Tag: greenhouse vertical farming

Are the viroid-like molecules the evolutionary link between the RNA and DNA world? We hope that the current and the future generations of citrus scientists will carry on the 80 years old journey of viroid research and that they will provide exciting answers, new discoveries, and even more questions for scientific advancement.Citrus exocorThis viroid , is a member of the genus Pospiviroid within the Pospiviroidae family. CEVd is the causal agent of exocortis disease characterised by bark scaling and dwarfing symptoms in sensitive citrus hosts commonly used as rootstocks and limiting crop production of the grafted commercial species. Since symptom expression takes 3-5 years to show on inoculated trifoliate orange Raf the biological characterization of CEVd usually relies on the use of indicator plants. Etrog citron has been widely used for indexing purposes, bio-amplification of the viroid RNA and strain characterization. Following infection with CEVd, Etrog citron displays a characteristic syndrome that includes severe stunting, leaf epinasty and midvein necrosis in 3-6 months. Furthermore, the effect of a severe isolate of CEVd on the gene expression of Etrog citron has been examined, using a citrus cDNA microarray approach that revealed that infection triggered important changes in chloroplast, cell wall, peroxidase and symporter activities. However the changes in gene expression found in CEVd infected Etrog citron may not be necessarily responsible for the bark scaling symptoms that are the most characteristic exocortis syndrome in trifoliate orange. Four trifoliate orange seedlings that were graft inoculated with a severe strain of CEVd and were planted in a field plot in June 1993,led grow lights developed the characteristic bark scaling symptoms, yellowing of the twigs and remained stunted as compared with the non-inoculated controls.

In 2010 plant material was collected in order to accomplish a gene expression analysis using the same genome-wide 20-K cDNA microarray developed under the Citrus Functional Genomic Project . For that, the gene expression profiles of the CEVd infected trifoliate oranges and uninfected control ones were compared. Subsequently, Significance Analysis of Microarrays was performed to identify those genes differentially expressed in both conditions and lastly, they were classified with gene ontology analysis by using the Blast2GO tool . As expected, results showed similarities and differences with those obtained for Etrog citron that could account for some of the differences found in the symptomatology. We developed a semi-automated, high throughput, RNA extraction and purification procedure optimized for citrus tissues. The system utilizes the SPEX SamplePrep’s Cryo-station and Geno Grinder 2010, and the Applied Biosystems’ MagMAXTM Express-96 along with a modified 5x MME-96 Viral RNA Isolation Kit. The detection of viral RNA with reverse transcription quantitative real time polymerase chain reaction requires high quality RNA as defined by concentration, purity, and integrity. RNA concentration and purity were assessed by spectrophotometry at 260 nm, and 260/280 and 260/230 ratios, respectively. The RNA concentration of 304 citrus samples ranged from 14.4 to 886.0 ng/μl with an average of 180.082 . The majority of the samples had concentrations ≥50ng/μl while 89.1% of the samples had concentrations of 50-400 ng/μl. The RNA purity ratios were higher than the desirable 1.8 for all samples tested with a mean value of 2.404 while 98% of the samples had 260/280 ratio ≥2.0. The 260/230 ratios had a broader variation in comparison to the 260/280. The 260/230 ratio mean value was 1.883 . The majority of the samples had the desirable 260/230 ratio of 1.8-2.0 .

The remaining 27% of the samples had 260/230 ratio of 1.0-1.7 and the remaining 11% had 260/230 ratio ˂1.0. Subsequent experimentation with adjusted grinding and washing buffers significantly improved and standardized the 260/230 ratios to the desirable values of 1.8-2.0.The RNA integrity of 23 samples was evaluated by 118 RT-qPCR reactions targeting the mRNA of the NADH dehydrogenase citrus gene. The mean Ct value of the RT-qPCR was 21.948 with maximum and minimum values 28.5 and 16.29, respectively. The cost of supplies for the presented RNA extraction and purification procedure was estimated at US$4.03 per sample. Citrus vein enation disease is characterized by woody galls on the trunk and vein enations on the leaves of susceptible citrus species. This disease is graft transmissible and naturally spread by aphid species in a persistent manner. With the aim of identifying the putative virus associated with vein enation, small interfering RNAs from three different field citrus trees that tested positive to citrus vein enation by indexing and that are located in Valencia, Tenerife and Gran Canaria, Spain, were analyzed by next generation sequencing Illumina technology. Bioinformatic analysis of individual samples allowed the identification of a new Luteoviridae present in the three samples. Bioinformatic analysis using the CLC Genomic Workbench, Velvet, Geneious and Bowtie software allowed the reconstruction of a sequence of 5077 nucleotides, corresponding to a new viral species for which the name Citrus vein enation virus is proposed. Open reading frames were identified coding for an hypothetical protein, the polymerase, the aphid transmission protein and the coat protein. Protein homology analyses for these ORFs showed similarities with Luteoviridae members: 44% , 66% , 62% and 70% , respectively. Specific primers and a TaqMan probe based on the new sequence were designed for real-time RTPCR detection of the agent.

The method allowed the successful detection of this virus in plant material and in various aphid species, even using direct systems of sample preparation. This novel diagnostic could greatly simplify and reduce the cost of routine detection of this highly prevalent disease in certification and sanitary programs.It is widely assumed that fleshy fruits are involved in mediating the attraction of seed dispersal organisms and the avoidance of consumption by seed predators. It is thought that the primary function of secondary metabolites present in immature fruits is to defend them against all types of potential consumers. Changes in size, texture, taste, aroma and color occur during ripening. Frugivores include not only legitimate dispersers such as vertebrates and birds but also less appreciated but more abundant consumers of fleshy fruits, microbes. Plant volatile organic compounds comprise a wide diversity of low-molecular-weight secondary metabolites, including terpenoids. In general, flowers and fruits release the widest variety of VOCs, with emission rates peaking before pollination and at ripening. Sweet orange fruits accumulate mainly terpenoids in mature peel oil glands,vertical grow system and Dlimonene accounts for about 97% of their content. In nature, D-limonene content is usually low in orange fruits during the 2 to 3 months post-anthesis; it then drastically increases when the fruit is still green but contains seeds and remains at a high level until the fruit becomes fully mature. To investigate the role of VOCs in mature fruit interactions with specialized pathogenic microorganisms, we have generated transgenic orange plants carrying a D-limonene synthase gene in antisense configuration. Transgenic expression caused a dramatic decrease in the accumulation of D-limonene in fruit peels, being about 80-100 times lower in AS samples than in empty vector transgenic ones. A global gene expression analysis of these fruits linked the decrease of D-limonene to the upregulation of genes involved in innate immunity. Additionally, this caused the activation of J jasmonic acid signalling and metabolism upon challenge with different economically important fungal and bacterial pathogens, which led to strong general resistance against Xanthomonas citri subsp. citri, Penicillium digitatum and PhyllocThista citricarpa in AS orange peels, indicating that D-limonene and related terpene accumulation not only attract legitimate seed dispersers but also facilitate infection by specialized microorganisms.Citrus tristeza viruscauses one of the most devastating diseases of citrus worldwide inducing the death of sweet orange, mandarin, lime and grapefruit trees budded on sour orange. The availability of a CTV-resistant rootstock with the sour orange attributes of productivity, fruit quality and tolerance to abiotic stresses would be a major benefit to the citrus industry worldwide. The objective of the field trial was to evaluate the response to CTV of 10 sour orange transgenic lines carrying CTV-derived sequences. They were obtained in the laboratories of IVIA, Spain and planted at the INTA Experiment Station in Concordia, Argentina where CTV is endemic and efficiently transmitted by the brown citrus aphid .

Rooted cuttings of transgenic sour orange lines were budded with non-transgenic and virus-free Valencia Late sweet orange . Valencia trees budded on tolerant rootstocks as well as on non-transgenic sour orange were planted as controls. Trees were planted in a complete randomized design with two trees per plot and 5 replications. Every six months imprints were taken to determine the progress of CTV infection in each tree. Based on direct immuno printing-ELISA, differences in disease progress were observed till June 2012 on the different transgenic rootstocks. By December 2012 the percentage of diseased trees was over 80%. The sudden increase in disease progress in the last semester could be due to post-freeze effects. Four years after planting, almost 100 % of the trees are CTV infected, showing stunted growth and yellowing of foliage. Trees from each transgenic line were grouped according to symptom severity in the field. The better looking trees were those of two of the ten transgenic lines carrying CTVderived sequences.Citrus tristeza disease was reported in Northeast Argentina in 1930 and in the Northwest in 1947. Later, millions of citrus trees on sour orange died from quick decline in both citrus regions. The most efficient vector, Toxoptera citricida and other aphids are present and consequently, the disease is endemic. Nowadays, citrus varieties are only grafted on tolerant rootstocks. Independent of rootstock, grapefruit is affected by stem pitting, and disease expression is severe in some selections. Biological characterization of Citrus tristeza virusisolates from Northwest Argentina has been carried out since 2008 in the Centro de Saneamiento de Citrus of the EEAOC although molecular identification of isolates has not been performed thus far. In order to identify isolates, a reverse-transcription polymerase chain reaction was performed. Five sets of genotype-specific CTV primers within the open reading frame -1a of well recognized genotypes were used for characterization. CTV isolates were collected from Citrus limon, C. sinensis, C. paradisi, C. reticulata C. reshni, C. latifolia, C. macrophylla, Poncirus trifoliata and Troyer citrangeaccording to the following criteria: species or cultivars of the source tree, visual symptoms on the source tree, and symptom expression in greenhouse tests with Mexican lime , Pineapple sweet orange , sour orange and Duncan grapefruit indicator plants. Most of the source trees showed no remarkable symptomatology in the field tree. Of the five CTV genotypes analyzed, severe genotypes were widely distributed, whereas mild isolates were detected at a very low incidence. The genotypes T3 and VT were predominant in mixed infections, independent of host species and variety. Data obtained are relevant because they complement existing information for CTV biological diversity in Northwest Argentina. This is the first characterization and classification of northwestern CTV isolates.Twelve Citrus tristeza virusisolates, collected from 5 different orchards in Hunan, China, were simultaneously characterized by RT-PCR of the p23 gene, capillary electrophoresis of single strand conformation polymorphisms of the p23, p25 and p27 genes as well as multiple molecular marker analysis with four standard isolates, namely T3, T30, T36, and VT. Results from RT-PCR of the p23 gene indicated that all the isolates were virulent. CE-SSCP and MMM characterization revealed high levels of genetic diversity among the isolates ranging from single genotype infections to highly mixed infections. Out of 12 isolates, 11 contained the T3 genotype, three being single T3 genotypes, two contained T3+VT and six had T3+VT+T36+T30. The remaining isolate was the VT+T36+T30 genotype. T3 and VT, reported to be virulent genotypes, are widely distributed in Hunan Province. As the isolates were from trees showing stem pitting, the single T3 profile of CE-SSCP was likely to be related to stem pitting. Further confirmation is to be performed with more samples showing obvious stem pitting symptoms. In young orchards, single genotype isolates are usually detected, and mixed ones are found in old orchards.The characterization by the three different molecular methods resulted in consistent results with some inconsistency among different methods. In the latter case, sequencing should be conducted for further characterization.Despite millions of trees being indexed by ELISA, Citrus tristeza disease continues to spread worldwide, confirming that quarantine restrictions, eradication, and tristeza-free propagation material are not enough to combat the virus once it becomes established in an area.

Resistant starch is a popular nutritional additive to produce food with enhanced quality attributes, i.e., higher fiber content, and starchy horticultural commodities are similarly attractive. Te yield penalty of high amylose crops may be alleviated by picking an ideal AP/AM ratio through a coordinate change in the relative balance of starch biosynthetic enzymes. In the case of potato, it is plausible that down regulation of SBEs not only produces healthy fiber-starch, but also lessens the CIS severity and acrylamide problem . However, the sugars derived from starch during CIS may be an adaptive mechanism to enhance plant chilling tolerance. Rapid sugar accumulation upon cold stress have been reported in fruit. Te sugars freed from starch may promote metabolic activity and serve as an osmoprotectant, thus alleviating chilling injury. Te major functional SBEs were found to be upregulated in cold-stressed banana fruit, potato tuber, and Arabidopsis leaf , which may facilitate the ‘sugaring’ process. Modulating SBE activities may alter the rate of sugar released from the highly digestible starch polymers, thus changing the fruit/tuber cold responses. In fruiting species, the importance of ‘transitory-storage starch’ may be underestimated due to the lack of enough direct knowledge of its function, gained from experimental data. Tomato serves as a functional genomics model for feshy fruit, as it is easily transformed and genetically manipulated. Te putative function of ‘transitory-storage starch’ in fruit ripening, respiration, and sweetness enhancement may be revealed by engineering AP/AM ratio through over expression or suppression of SBEs. We hypothesize that high amylose, resistant starch tomato fruit may have reduced available starch, sugars,nft hydroponic system and changes in fruit ripening and other processes that are dependent on starch as a carbon supply and source of energy post harvest.

Tomato SBEs may not reflect the functionality of all fruit SBEs, but it would produce fundamental knowledge and expand our understanding of species-, organ- and developmental-specific regulations of the core starch biosynthetic enzymes.Starch, in general, plays an essential role in balancing the plant’s carbon budget as a reserve of glucose that is tightly related to sucrose metabolism and sugar signaling pathways.Starch is considered as an integrative mediator throughout the plant life cycle, regulating plant vegetative growth, reproductive growth, maturation and senescence, and response to abiotic stresses. This comprehensive regulation is achieved by changes in the synthesis and degradation of starch to balance glucose levels, after developmental and environmental triggers in different organs. Transitory starch and its biosynthesis have been well studied in the model plant Arabidopsis, but little research has been conducted on post harvest leafy greens. Quality metrics such as shelf-life, favor, color, firmness, and texture are of consumers’ choice, and they are related to the limited pools of storage compounds in detached leaves, which cells rely on to maintain basic cellular activities. A hypothesized function for the starch in packaged leaves could be presented as such: starch may act as a buffer against sugar starvation, and protect against cellular autophagy, by serving as an alternative energy source . If the biosynthesis and degradation of starch could be adjusted in a controlled way, then the modulated release of sugars may influence the post harvest shelf-life in detached leafy greens . A continuous, paced supply of sugars may preserve vacuolar nutrients and water content, leaf cellular structure and integrity, and, thus extend the ‘best by’ post harvest date of the produce. Although the eco-physiological role of amylose is poorly understood in Arabidopsis, the AP/AM ratio may set a threshold for the optimum usage of starch.

SBE action in leafy crops may differ from those in Arabidopsis given the dissimilar numbers of their isoforms and domain features . Modifying the quantity and quality of the starch in leafy greens such as spinach, lettuce, and watercress, by targeting starch biosynthetic enzymes, may provide evidence to its post harvest function in terms of produce longevity. Resistant starch is a popular nutritional additive to produce food with enhanced quality attributes, i.e., higher fiber content, and starchy horticultural commodities are similarly attractive. Te yield penalty of high amylose crops may be alleviated by picking an ideal AP/AM ratio through a coordinate change in the relative balance of starch biosynthetic enzymes. In the case of potato, it is plausible that down regulation of SBEs not only produces healthy fiber-starch, but also lessens the CIS severity and acrylamide problem . However, the sugars derived from starch during CIS may be an adaptive mechanism to enhance plant chilling tolerance. Rapid sugar accumulation upon cold stress have been reported in fruit. Te sugars freed from starch may promote metabolic activity and serve as an osmoprotectant, thus alleviating chilling injury. Te major functional SBEs were found to be upregulated in cold-stressed banana fruit, potato tuber, and Arabidopsis leaf , which may facilitate the ‘sugaring’ process. Modulating SBE activities may alter the rate of sugar released from the highly digestible starch polymers, thus changing the fruit/tuber cold responses. In fruiting species, the importance of ‘transitory-storage starch’ may be underestimated due to the lack of enough direct knowledge of its function, gained from experimental data. Tomato serves as a functional genomics model for feshy fruit, as it is easily transformed and genetically manipulated. Te putative function of ‘transitory-storage starch’ in fruit ripening, respiration, and sweetness enhancement may be revealed by engineering AP/AM ratio through overexpression or suppression of SBEs. We hypothesize that high amylose, resistant starch tomato fruit may have reduced available starch, sugars, and changes in fruit ripening and other processes that are dependent on starch as a carbon supply and source of energy post harvest.

Tomato SBEs may not reflect the functionality of all fruit SBEs, but it would produce fundamental knowledge and expand our understanding of species-, organ- and developmental-specific regulations of the core starch biosynthetic enzymes.Cell size correlates strongly with key aspects of cell physiology, including organelle abundance and DNA ploidy. Maintenance of uniform size may also underlie the efficient functioning of tissues and organs. While cells employ diverse strategies to regulate their size in different situations, it is unclear how these mechanisms are integrated to provide robust, systems-level control. In budding yeast, a molecular size sensor restricts passage of small cells through G1, enabling them to gain proportionally more volume than larger cells before progressing to Start . In contrast, size control post-Start is less clear. The duration of S/G2/M in wild type cells has been reported to exhibit only a weak dependence on cell size, so larger cells would be expected to add a greater volume than smaller ones. Yet it is also the case that even large mother cells produce smaller daughter cells, suggesting that additional regulation may play a role during S/G2/M, either by limiting bud growth rate or shortening the duration of budding. There is also conflicting evidence regarding the molecular size control mechanisms that might operate during S/G2/M, such as whether the kinase Swe1,mobile grow rack the budding yeast homolog of fission yeast Wee1, regulates growth by sensing bud size or bud morphogenesis. Furthermore, while G1 size control mechanisms act on cells smaller than their set-point size, no mechanisms have been clearly defined to limit size as cells become larger. Since physiological perturbations can result in abnormally large cells, mechanisms must exist to ensure cells that grow too large are able to return to the set-point volume after successive rounds of growth and division. Underscoring the importance of this aspect of size homeostasis, tumor cells lacking functional size-homeostasis pathways often grow far larger than normal. In sum, how cells regulate size during S/G2/M and whether such mechanisms might enforce an upper limit on cell volume remains an important open question. To gain further insight into post-Start size control, we prepared ‘giant’ yeast using two approaches to reversibly block cell cycle progression but not growth: optogenetic disruption of the cell polarity factor Bem1 or a temperature sensitive cdk1 allele. We reasoned that giant yeast would satisfy pre-Start size control while enabling us to uncover post-Start size-limiting mechanisms though the identification of invariant growth parameters . Upon release from their block, giant mothers reentered the cell cycle and populations of their progeny returned to their unperturbed size within hours. Volume regulation in these cells was inconsistent with two major classes of size control mechanisms: an ‘adder’ specifying a constant volume increment added over the course of a cell cycle and a ‘sizer’ specifying daughter cell volume. Instead, our data support a ‘timer’ mechanism that specifies the duration of S/G2/ M across the full range of daughter sizes. Our data thus provide evidence that cell size homeostasis is maintained by at least two separable mechanisms of size control: a pre-Start size sensor enabling size-dependent passage through Start, and a post-Start timer ensuring that daughters are smaller than their mothers. Together, these mechanisms ensure that yeast populations generated from cells at either size extreme rapidly return to a set-point within only a few cell division cycles.To achieve reversible control over cell size in the budding yeast S. cerevisiae, we first took advantage of the light-responsive PhyB/PIF optogenetic system to control the localization of Bem1, a cell polarity factor. In this “optoBem1” system, red light illumination relocalizes the PIF-Bem1 fusion protein to mitochondria-anchored PhyB . Light induced Bem1 re-localization produces an acute loss-of-function phenotype where cells fail to form a site of polarized Cdc42 activity, fail to initiate budding, and instead undergo continuous isotropic growth.

Strikingly, this effect is quickly reversed upon illumination with infrared light, which releases PIF-Bem1 from the mitochondria within seconds. Upon release, cells form a bud within minutes and proceed to cytokinesis . The PIF-Bem1 fusion protein appears to fully recapitulate normal Bem1 function: when it is not sequestered to the mitochondria, overall cell sizes and cell growth rates are similar to an isogenic wild type strain. We performed additional experiments to more completely characterize optoBem1 giant cells. Our initial experiments quantifying the growth of red light-illuminated optoBem1 cells revealed two sub-populations of cells that grew at different rates . We hypothesized that cell growth rates differed depending on the cell cycle phase at the time of Bem1disruption. Indeed, we found that synchronizing optoBem1 cells before red light stimulation led to unimodally-distributed growth . Furthermore, restricting our analysis to measure growth only following entry into G1 yielded a unimodal distribution . We also observed that a substantial fraction of optoBem1 yeast burst as they become increasingly large , and hypothesized that cell lysis may be a result of large cells’ increased susceptibility to osmotic pressure. Supporting this hypothesis, growing cells in high-osmolarity media containing 1 M sorbitol decreased the frequency of cell lysis without affecting the rate of isotropic growth . We therefore supplemented our media with sorbitol for all subsequent experiments involving optoBem1-arrested cells. Finally, to test whether growth was isotropic during the entire time period, we pulsed cells with fluorescent Concanavalin A to mark the existing cell wall, followed by a washout of free FITC-ConA. We found that cells exhibited uniform dilution of FITC-ConA around their surface, consistent with isotropic growth .Prior studies have established that unperturbed, freely-cycling budding yeast cells appear to exhibit an exponential growth in volume over time. However, most of this growth is localized to the bud, with only a minor contribution from the mother cell’s isotropic growth during G1.Since distinguishing between growth patterns is difficult to achieve during the growth interval of normal sized yeast, we reasoned that the ability to prepare isotropically-growing yeast with volumes spanning an order of magnitude would permit high-quality measurements of this growth law, and potentially reveal processes that limit cell growth as size increases.We imaged optoBem1 cells during red light illumination at multiple z-planes and used a custom code to automatically measure cell diameter every 10 min over a 12 h period. Following entry into G1 after Bem1 arrest, we found that isotropically-growing optoBem1 cells exhibited a linear increase in cell diameter over time, corresponding to a rate of volume growth proportional to 3 . Since these volume increases also show a strong correlation with protein content, as assessed by fluorescence , our data suggest that the growth we observed primarily arises from increases in cell mass rather than cell swelling . This result is inconsistent with two classic models of cell growth: a constant growth law, where volume increases linearly over time; and exponential growth, where the rate of growth is proportional to the cell’s current volume. In contrast, a linear increase in cell diameter is the expected result for volume increasing in proportion to cell surface area .

Despite the physiological relevance of the BIA assumptions and the number of BIA studies, a suitable solution for the characterization of the current pathways in roots is missing. Thus far, only indirect information obtained from invasive and time-consuming experiments have been available to address this issue . Mary et al. , and Mary et al. 2020 tested the combined use of ERT and Mise A La Masse methods for imaging grapevine and citrus roots in the field. An approach hereafter called inversion of Current Source Density was used to invert the acquired data. The objective of this inversion approach is to image the density and position of current passing from the plant to the soil. The current source introduced via the stem distributes into “excited” roots that act as a distributed network of current sources . Consequently, a spatial numerical inversion of these distributed electric sources provides direct information about the root current pathways and the position of the roots involved in the uptake of water and solutes. The numerical approach used to invert for the current source density is a key component required for such an approach. Mary et al. used a nonlinear minimization algorithm for the inversion of the current source density. The algorithm consisted of gradient-based sequential quadratic programming iterative minimization of the objective functions described in Mary et al. . The algorithm was implemented in MATLAB, R2016b, using the fmincon method.

Because no information about the investigated roots was available,flood and drain tray the authors based these inversion assumptions and the interpretation of their results on the available literature data on grapevine root architecture. Consequently, Mary et al. highlighted the need for further iCSD advances and more controlled studies on the actual relationships between current flow and root architecture. In this study, we present the methodological formulation and evaluation of the iCSD method, and discussits applications for in-situ characterization of current pathways in roots. We perform our studies using laboratory rhizotron experiments on crop roots. The main goals of this study were: 1) develop and test an iCSD inversion code that does not rely on prior assumptions on root architecture and function; 2) design and conduct rhizotron experiments that enable an optimal combination of root visualization and iCSD investigation of the current pathways in roots to provide direct insight on the root electrical behavior and validate the iCSD approach; and 3) perform experiments to evaluate the application of the iCSD method on different plant species and growing medium that are common to BIA and other plant studies.The relationship between hydraulic and electrical pathways has been the object of scientific debate because of its physiological relevance and methodological implications for BIA methods .The distribution of the current leakage is controlled by 1) the electrical radial and longitudinal conductivities , and 2) by the resistivity contrast between root and soil.

With regard to σcr and σcl, when σcl is significantly higher than σcr, the current will predominantly travel through the xylems to the distal “active” roots, which are mostly root hairs. Based on the link between hydraulic and electrical pathways, this is consistent with a root water uptake process where root hairs play a dominant role while the more insulated and suberized roots primarily function as conduits for both water and electric current . On the contrary, if the σcr is similar to σcl, the electrical current does not tend to travel through the entire root system but rather starts leaking into the surrounding medium from root proximal portions. The coexistence of proximal and distal current leakage is in line with studies that suggest the presence of a more diffused zone of RWU, and a more complex and partial insulation effect of the suberization, possibly resulting from the contribution of the cell-to-cell pathways . Soil resistivity can affect the distribution of the current leakage by influencing the minimum resistance pathways, i.e., whether roots or soil provide the minimum resistance to the current flow. In addition, soil resistivity strongly relates to the soil water content, which, as discussed, affects the root physiology. Therefore, information on the soil resistivity, such as the ERT resistivity imaging, has the potential for supporting the interpretation of both BIA and iCSD results. Dalton proposed a model for the interpretation of the plant root capacitance results in which the current equally distributes over the root system. Because of the elongated root geometry this model is coherent with the hypothesis of a low resistance xylem pathway . Numerous studies have applied Dalton’s model documenting the predicted correlation between root capacitance and mass . In fact, recent studies with wheat, soy, and maize roots continue to support the capacitance method .

Despite accumulating studies supporting the capacitance method, hydroponic laboratory results of Dietrich et al. and other studies have begun to uncover potential inconsistencies with Dalton’s assumptions. In their work, Dietrich et al. explored the effect of trimming submerged roots on the BIA response and found negligible variation of the root capacitance. Cao et al. reached similar conclusions regarding the measured electrical root resistance . Urban et al. discussed the BIA hypotheses and found that the current left the roots in their proximal portion in several of their experiments. Conclusions from the latter study are consistent with the assumption that distal roots have a negligible contribution on root capacitance and resistance. Because of the complexity of the hydraulic and electrical pathways, their link has long been the object of scientific research and debate. For recent reviews see Aroca and Mancuso ; for previous detailed discussions on pathways in plant cells and tissues see Fensom , Knipfer and Fricke , and Findlay and Hope ; see Johnson and Maherali et al. in regard to xylem pathways. See Jackson et al. and Hacke and Sperry for water pathways in roots. Thus, above discrepancies in the link between electrical and hydraulic root properties can be, at least to some degree, attributedto differences among plant species investigated and growing conditions. Among herbaceous plants,hydroponic equipment maize has been commonly used to investigate root electrical properties . For instance, Ginsburg investigated the longitudinal and radial current conductivities of excited root segments and concluded that the maize roots behave as leaking conductors. Similarly, Anderson and Higinbotham found that σcr of maize cortical sleeves was comparable to the stele σcl. Recently, Rao et al. found that maize root conductivity decreases as the root cross-sectional area increases, and that primary roots were more conductive than brace roots. By contrast, BIA studies on woody plants have supported the hypothesis of a radial isolation effect of bark and/or suberized tissues.Plant growing conditions have been shown to affect both water uptake and solute absorption due to induced differences in root maturation and suberization . Redjala et al. observed that the cadmium uptake of maize roots grown in hydroponic conditions was higher than in those grown aeroponically. Tavakkoli et al. demonstrated that the salt tolerance of barley grown in hydroponic conditions differed from that of soil-grown barley. Zimmermann and Steudle documented how the development of Casparian bands significantly reduced the water flow in maize roots grown in mist conditions compared to those grown hydroponically. During their investigation on the effect of hypoxia on maize, Enstone and Peterson reported differences in oxygen flow between plants grown hydroponically and plants grown in vermiculite. The results reported above and in other investigations are conducive to the hypothesis that root current pathways are affected by the growing conditions, as suggested in Urban et al. .

For example, the observations by Zimmermann and Steudle and Enstone and Peterson may explain the negligible contributions to the BIA signals from distal roots under hydroponic conditions . At the same time, the more extensive suberization in natural soil and weather conditions could explain the good agreement between the rooting depth reported by Mary et al. based on the iCSD and the available literature data for grapevines in the field. To minimize these ambiguities and to develop a more robust approach for non-invasive in-situ root imaging, we aim to develop iCSD inversion code that does not rely on prior assumptions on root architecture and function and use rhizotron experiments to validate the iCSD approach.The phrase “inversion of Current Source Density” was introduced by Łęski et al. to describe the 2D imaging of current sources associated with the brain neural activation. Similar inversion methodologies have been developed for the interpretation of the self potential data, where the distribution of naturally occurring currents is investigated . With regard to active methodologies, Binley et al. developed an analogous approach for detecting pollutant leakage from environmental confinement barriers. Although there are physical and numerical intrinsic differences between application of the iCSD to detect brain neuronal activity and current pathways in roots, we decided to adopt the term iCSD as the general physical imaging of current source density remains valid. With iCSD, we indicate the coupling of ERT and MALM through the proposed numerical inversion procedure for the imaging of the current source density, and its correlation with root architecture. We introduce the necessary aspects regarding the ERT and MALM methods in this section. However, we direct the inTherested readers to more in-depth discussion about the ERT method , and to Schlumberger and Parasnis with regard to the MALM method. In the following discussion we use ρmed to represent the 2D or 3D distribution of the electrical resistivity in the growing medium . CSD represents the 2D, or 3D, distribution of the Current Source Density within the same medium. In the case of roots, the CSD is controlled by the current conduction behavior of the roots, specifically by the leakage pattern of the root system . Both ERT and MALM are active methods. In these methods the current is forced through the medium by applying a potential difference between two current electrodes. In ERT, both current electrodes are positioned in the investigated medium, while for MALM the positive current pole is installed in the plant stem,similar to BIA . The potential field resulting from the current injection depends on CSD, resistivity of the medium , and boundary conditions. The boundary conditions are known a priori and their impact on the potential field can be properly modeled. In ERT, the current sources correspond to the electrodes used to inject current, allowing us to invert for ρmed. Then, the iCSD accounts for the obtained ρmed and explicitly inverts the MALM data to obtain current source distribution.The rhizotrons used in this study were designed to enable the concurrent direct visualization of the roots and electrical measurements. Rhizotron dimensions were 52 cm × 53 cm × 2 cm , see Fig. 2. Figure 2a shows the rhizotron setup with 64 silver/silver chloride electrodes located on the back viewing surface. The viewing surfaces were covered with opaque material to stop the light from affecting the development of the roots. The back viewing surface was removable, allowing homogeneous soil packing for the plant experiments and convenient access to the electrodes. Besides the top opening, the rhizotrons were waterproof to enable hydroponic experiments and controlled evapotranspiration conditions during the soil experiments and plant growth. All the experiments were performed in a growth chamber equipped with automatic growth lights and controlled temperature and humidity. The temperature varied with a day/night temperature regime of 25/20 °C. The humidity ranged from 45 to 60%. For both ERT and MALM methods, the electrical potential field is characterized by a set of potential differences measured between pairs of electrodes. It is important to properly arrange the electrodes on the rhizotron viewing surface and design a suitable acquisition sequence to obtain a good sensitivity coverage of the investigated system . This is particularly true for the iCSD, as both ERT and MALM acquisitions affect its result. The 64 electrodes were arranged in a 8 by 8 grid on the back viewing surface of the rhizotron, leaving the front surface clear for the observation . For the ERT, the designed arrangement of the electrodes offers a good compromise between a high coverage on the central part of the rhizotron, which encompasses the root zone, and a sufficient coverage on the rhizotron sides to avoid an excessive ERT inversion smoothness. For the MALM, the arrangement of the electrodes is highly sensitive to the position of the investigated current sources.

Downstream firms transform the paste in final consumer products. According to the Food Institute, at the end of the process, raw material account for 39%-45% of total production cost. According to the ERS, there was a radical structural change in the processing industry in the late 1980’s and early 1990’s. A period of relatively high prices in the late 1980s triggered new investments. This finally resulted in excess supply and decreasing prices. As a consequence, many processors went bankrupt and the whole industry was restructured. The current structure is the result of such adjustments.A brief industry description highlights two key points prior to the estimations. Price expectations. The majority of production is sold under contract. This has two implications: i) producers know prices when planning production, so we do not need to model expectations; rather we assume perfect information, ii) the actual contract price is unobservable, being industry private information.We use the spot price as a proxy for the real contract price. However, since the measurement error is likely to be correlated with the error terms in the production equations we use an instrumental variable approach. The instrument is the previous year’s spot price, which is correlated with the current spot price, but uncorrelated with random shocks in current production. Structural change. The industry underwent structural changes from the late ‘80s until the early ‘90s. Much of the change is likely due to continued expansion in food-service demand, especially for pizza, taco,4×8 flood tray and other Italian and Mexican foods .

Increased immigration and changes in America’s tastes and preferences have contributed to rising per capita tomato use . Commercial varieties were developed to expedite packing, shipping, and retailing in the processing market. Mechanical harvesting and bulk handling systems replaced hand harvest of processing tomatoes in the California in the 1960’s as the new varieties were introduced. Increases in yields are due to the development of higher yielding hybrid varieties and improved cultural practices such as increases in use of transplanting . The hypothesis of structural change was tested on both the supply and demand side.The acreage model was estimated assuming a partial adjustment process. Price expectations have been modeled using the previous year’s price for the period 1960-1987 and a two-year lagged price before the period 1988-2002. This was done because after the structural change, the prices exhibits an alternate pattern, so that the current price is negatively correlated with the previous year, but positively correlated with two periods before. Finally we tested the influence of the processing industry on the fresh tomato acreage, by using the price of processing tomato as a regressor. What accounts for the structural break in 1987 in fresh tomato acreage? Much of the increase in California acreage can be explained as a response to changes in consumption patterns, according to the USDA. In terms of consumption, tomatoes are the Nation’s fourth most popular fresh-market vegetable behind potatoes, lettuce, and onions. Fresh-market tomato consumption has been on the rise due to the enduring popularity of salads, salad bars, and sandwiches such as the BLT and subs. Perhaps of greater importance has been the introduction of improved tomato varieties, consumer interest in a wider range of tomatoes , a surge of immigrants with vegetable-intensive diets, and expanding national emphasis on health and nutrition.

After remaining flat during the 1960s and 1970s at 12.2 pounds, fresh use increased 19 percent during the 1980s, 13 percent during the 1990s, and has continued to trend higher in the current decade. Although Americans consume three-fourths of their tomatoes in processed form , fresh-market use exceeded 5 billion pounds for the first time in 2002 when per capita use also reached a new high at 18.3 pounds. Because of the expansion of the domestic greenhouse/hydroponic tomato industry since the mid-1990s, it is likely per capita use is at least 1 pound higher than currently reported by USDA . One medium, fresh tomato has 35 calories and provides 40 percent of the U.S. Recommended Daily Amount of vitamin C and 20 percent of the vitamin A. University research shows that tomatoes may protect against some cancers.The own price elasticity of tomatoes is estimated to be -0.32, which is highly statistically significant. Therefore demand for fresh tomatoes is relatively inelastic with respect to changes in retail prices. The own-price elasticity of carrots is -0.53 and for lettuce it is -0.71. The estimate of the own price elasticity of cabbage is positive at 0.12, which is counter intuitive. This finding, however, is not statistically significant. The estimated second-stage expenditure elasticities are all positive and range in values from 0.89 to 1.44. In all cases the expenditure elasticities are statistically significant. All of the cross prices elasticities are negative indicating that the four fresh vegetables are complements. Only the complementarities between tomato quantity with carrot and lettuce prices are statistically significant.Models for both fresh and processed tomatoes were developed and estimated. An almost ideal demand subsystem was estimated for four fresh vegetables that included tomatoes, carrots, lettuce, and cabbage. The second-stage own-price elasticities were all inelastic except for cabbage which was unexpectedly positive. The conditional expenditure or income elasticites varied from 0.89 for fresh tomatoes to 1.44 for carrots. All of the cross-price elasticities were negative indicating that the four fresh vegetables aregross complements. A plausible explanation for this is that the four commodities are used in salads, especially given that no significant complementarities were found with respect to fresh cabbage.

Ordinary least squares and instrumental variable techniques were used to obtain estimated partial adjustment acreage functions of processing tomatoes. The estimated short-run own-price elasticity estimates were between 0.47 and 0.41. Chow tests confirmed a possible structural break in the acreage function for processed tomatoes around 1988. One possible explanation of the break is the increase use of contracts around this time period. Estimated own-price elasticities for processed tomatoes in the production function varied between 0.45 and 0.55. Producers respond to prices increases in a positive manner, in accordance with theory. With respect to demand for processing tomatoes, the own-price elasticity was estimated to be – 0.18 and the cross-price estimated elasticity of tomato paste on processing tomatoes was 0.16. Thus, as the price tomato paste increases the derived demand for processed tomatoes increases, as expected. For the second period the estimated own-price elasticity in the acreage equation was 0.23 indicating that producers respond positively to increases in prices. The short-run elasticity of fresh tomato production with respect to price was 0.22 prior to 1987 and 0.27 after 1987. Thus, through out the sampling period, the own-price elasticity in the fresh tomato production function was found to be inelastic. The exchange of CO2 between forested ecosystems and the atmosphere has received significant attention in recent years in the context of global carbon cycling. In contrast, the role of forests as sources or sinks of less abundant carbon trace gases such as methane , methanol,indoor garden and other volatile organic carbon compounds is relatively poorly understood. It is challenging to measure the atmospheric exchange of such gases because of low fluxes and high spatial variability, yet scaled over large areas the mass flux of these compounds is sufficient to influence atmospheric chemistry and climate. Methane is particularly noteworthy because it is an important greenhouse gas, contributing about 20% of current radiative forcing, and a key compound governing hydroxyl radical concentrations that regulate much atmospheric chemistry. This paper provides a brief review of recent evidence suggesting that our knowledge of CH4 production in upland forests is insufficient to meet the demand for accurate accounting of radiatively active gas sources. It was motivated by the groundswell of interest that followed the first report of CH4 production by aerobic plant tissues . We begin with an overview of CH4 cycling because the topic is unfamiliar to many tree physiologists.Our current understanding is that CH4 is an end product of organic carbon degradation performed by a consortium of microbes in an O2-free environment . After a series of hydrolytic and fermentation reactions that simplify complex organic matter, microorganisms within the domain Archaea—the methanogens—produce CH4 as a respiratory end product of either H2 oxidation coupled to CO2 reduction, or acetate fermentation. Because methanogens are poor competitors for H2 and acetate, their activity is suppressed by other microbes that couple oxidation of the same electron donors to the reduction of nitrate, ferric iron and sulfate . Exposure to O2 inhibits methanogens indirectly by regenerating oxidized forms of N, Fe and S that support competing microorganisms, and directly through O2 toxicity.

Methane can be produced in soils without being emitted to the atmosphere because it is also consumed by aerobic microorganisms that oxidize CH4 to CO2. Methanotrophic bacteria grow by coupling the oxidation of CH4 to the reduction of O2. They are ubiquitous in soils and explain why upland soils are generally net CH4 sinks . Despite much research on methanotrophs in upland soils, there are no isolates of these organisms to date and little is known about their ecology. To our knowledge, no one has investigated the possibility that methanotrophs exist on the surfaces of upland plants. However, they occur symbiotically on Sphagnum tissues where they provide CO2 to support photosynthesis . Methane is produced abiotically from combustion of organic carbon during biomass burning and by thermal alteration of sedimentary organic carbon. It has been proposed that CH4 is produced abiotically in aerobic plant tissues .Despite generally inhospitable conditions, there is abundant evidence of methanogenic activity in upland soils. Andersen et al. used a 14CH4-labeling technique to infer that two forest soils produced CH4 even though the soils as a whole were net CH4 sinks. von Fischer and Hedin used a stable isotope technique to make direct measurements of gross CH4 production in 130 soil cores from 17 sites and found that even dry, oxic soils produced CH4. Aerobic forest and agricultural soils have been reported to switch from net CH4 uptake to CH4 emission in the presence of a compound that blocks CH4 oxidation . Finally, upland soils incubated anaerobically begin producing CH4 within days or weeks . Collectively, these studies suggest that upland soils harbor populations of methanogens and are capable of becoming net sources of CH4 when sufficiently wet. The possibility of CH4 production in upland soil microsites is consistent with the occurrence of denitrification and Fe reduction in upland soils, and observations that acetate, a CH4 precursor, is found in upland soils . Although studies of methanogen isolates suggest they are extremely O2 sensitive, other evidence suggests that they can tolerate a certain amount of O2 . Methanogens have been reported to survive long periods in dry and oxic soils , perhaps protected from O2 by reactive soil minerals . The evidence that upland soils can support low rates of methanogenesis suggests that CH4 oxidizing bacteria consume CH4 from two sources, the atmosphere and the soil itself . The juxtaposition of these sources may explain a puzzling observation about the response of CH4 fluxes to changes in soil water content. Andersen et al. reported that an intact upland forest soil core left uncovered at room temperature changed from a net sink for atmospheric CH4 to a net source. Isotopic data showed that CH4 oxidation fell to almost zero over this period, suggesting that CH4 oxidizing bacteria attached to soil surfaces were more sensitive to soil drying than methanogens buried in the anaerobic center of soil aggregates. The cessation of CH4 oxidation could have been caused by a physiological drought response among methanotrophic bacteria, more rapid CH4 diffusion from the soil to the atmosphere due to low tortuosity , or both. In other circumstances, decreases in soil water content can enhance CH4 oxidation in upland soils by increasing CH4 diffusion from the atmosphere into soil pore spaces . In addition to microsites, anaerobic conditions occur in saturated zones that coincide with the water table surface. Soils with a deep source of CH4 have a soil CH4 concentration profile characterized by two maxima—one at the soil surface and the other near the water table—separated by a minimum. Such profiles have been observed in a variety of upland ecosystems, including desert , temperate hardwood forest and temperate coniferous forest . It is possible that plants transport CH4 from a deep groundwater source through the transpiration stream, effectively bypassing the zone of CH4 oxidation . The most direct evidence of methanogenesis in upland soils is that they occasionally emit CH4 to the atmosphere.

We plotted the highlighted spectral bands into Fig. 3, and it is seen that the selected spectral bands in each LDA-based classification were located near known pigment peaks involved in photosynthesis and/or near spectral bands used in published indices to predict chlorophyll or nitrogen content in leaves. Thus, it appears that seed germination may be successfully classified based on reflectance in narrow spectral bands associated with the primary metabolism function and performance of plants. Although this study has demonstrated proof of concept in the potential utilization of machine-vision systems for managing ex situ seed resources several questions remain. Seeds in this study were aged under artificial conditions so the seed coat changes detected using hyperspectral analysis may not be indicative of changes that occur to seeds when stored under standard seed bank conditions. Across the plant kingdom, seeds vary greatly in colors, color patterns, shapes, and sizes. In addition, they have species-specific responses to environmental conditions. Different classification algorithms were therefore used for each of the three seed species, and successful use of this technology among other native plant species will require development of species specific classification algorithms. Availability of machine-vision systems to automate non-destructive assessments of seed germination may greatly improve the management of seed banks in future once further more detailed assessments of the technology are undertaken. Indeed, it may also be possible that such machine-vision systems can be used in advanced research into seed dormancy and other studies of seeds and their responses to environmental conditions and thus provide fresh insights into the underlying seed biology and physiology.

California organic strawberry producers face the challenge of controlling soil borne diseases,ebb and flow bench notably Verticillium wilt caused by Verticillium dahliae, Fusarium wilt caused by Fusarium oxysporum and charcoal rot caused by Macrophomina phaseolina . The main approach used to control these pathogens is crop rotation, however, many of the vegetable crops that can economically be rotated with strawberry are also hosts to one or more of the pathogens. Brassica species, notably broccoli have been found to suppress V. dahliae , but other key crops like lettuce are hosts. Furthermore, microsclerotia of V. dahliae can persist in the soil for many years. There is a clear need for additional disease control strategies and two that have shown promise are anaerobic soil disinfestation and use of mustard seed meals . Anaerobic soil disinfestation was developed in Japan and The Netherlands and has been shown to control soilborne pathogens and nematodes in strawberries. Previous studies conducted were aimed at optimizing ASD for California strawberry systems, and in conventional systems ASD was shown to be consistently effective at suppressing Verticillium dahliae in coastal California when 20 t ha-1 of rice bran was pre-plant incorporated and 75 to 100 mm of irrigation was applied in sandy-loam to clay-loam soils . California berry growers have started to adopt ASD at a commercial scale with ASD acreage increasing from 2 ha to over 400 ha in the last four years , the majority in organic production.It has also been evaluated in strawberry systems and showed neutral to positive effects on fruit production and disease suppression when used alone or in combination with other non-fumigant approaches such as ASD. Here we report on a recent rotation experiment testing ASD and MSM in a long term organic field site, and some large scale field demonstrations carried out in two different regions of California.In June 2011, a 4 replicate randomized block split-plot experiment with crop rotation as the main plots and ASD, mustard seed meal , ASD+ MSM, and untreated control as sub plots was established at the Center for Agroecology and Sustainable Food Systems organic farm on the University of California, Santa Cruz campus.

After strawberries, a legume/cereal mix winter cover crop was planted and followed with summer lettuce in all treatment plots. For management details see Zavatta et al. . Briefly broccoli ‘Gypsy’ and cauliflower ‘Snow crown’ were grown from June to September 2011 as main plots which were split prior to planting strawberries. For ASD plots, 20 t ha-1 of rice bran was applied to the bed surface and rototilled to 15 cm depth. For MSM plots 3.4 t ha-1 MSM was incorporated. For ASD+MSM plots, 16.9 t ha-1 of rice bran and 3.4 t ha-1 of MS were applied. ASD and ASD+MSM plots were drip irrigated to create and sustain anaerobic conditions for 3 weeks with a total of 108 mm of water applied. Strawberry plants ‘Albion’ were transplanted in November 2011, and fruit yield monitored from 20 plants bi-weekly from April to September 2012. A legume/cereal cover crop , 45% vetch , 10% rye was planted in all plots in the fall 2012 and grown until the following spring at which time they were mowed and incorporated into the soil. Romaine lettuce ‘Salvius’ was grown in the summer 2013. The numbers of viable V. dahliae microsclerotia in 0-15 cm of soil were estimated using a modified Anderson sampler and NP10 selective medium before and after each crop, and pre- and post-ASD treatment. V. dahliae infection on strawberry plants was evaluated at the end of the growing season for four plants per plot. A split plot ANOVA was used for statistical analysis. Two non-replicated large-scale ASD demonstration trials were conducted at a grower’s farm in Watsonville, California during the 2012-2013 growing season. One trial was on conventionally farmed land and the other in a nearby organic field. Main treatments were ASD using rice bran at 20 t ha-1 or RB 10 t ha-1 + Molasses 10 t ha-1, and subtreatments with or without pre-plant fertilizer. For the conventional field, a 673 kg ha-1 of slow release fertilizer was added pre-plant, and for the organic site feather meal at a rate of 1,122 kg ha-1. For ASD, RB 20 or 10 t ha-1 was broadcast onto the assigned plots and rototilled to a depth of 15 cm. Beds were formed, drip tapes and plastic mulch applied, and the first irrigation began two days later. Mol was diluted with water at 1:2 to 1:5 in a water tank prior to application, then 6.5 t ha-1 was applied through the drip tapes. Seven days later,hydroponic growing the remaining Mol was applied in the same manner. All plots were intermittently drip irrigated for three weeks from the first irrigation, with total irrigation amount of 60-75 mm. Soil Eh at 15 cm depth was monitored continuously using ORP sensors connected to a datalogger. Strawberries were harvested from 4 sections of each plot bi-weekly from March 19 to October 28, 2013.

A second strawberry demonstration trial was established in Oxnard, CA, in August 2014 with unreplicated 0.4 ha blocks of treatments of ASD RB 20 t ha-1, ASD RB 15 t ha-1, MSM 5.6 t ha-1 and grower standard practices. A 2.24 t ha-1 of pre-plant organic fertilizer was applied only to the grower standard plot. The same treatments, except for the RB 15 t ha-1 plot, had been applied to the same plots for the previous strawberry crop which was followed by a wheat cover crop incorporated in early August 2014. Instead of RB 15 t ha-1, the previous treatment had been ASD using RB 6.7 t ha-1 plus MSM 4.5 t ha-1 as Csources. RB and MSM were both applied on August 25 by broadcaster then beds shaped, drip lines added and TIF plastic tarp laid down. Approximately 200 mm of water was applied during ASD. Anaerobic conditions and soil temperatures were measured during ASD as above, and strawberries were harvested by the grower from January to May 2015. Plant mortality was measured by counting dead or nearly dead plants in each plot. Soil samples were taken from 0 to 6 inch depth in all plots post-treatment for microbial analysis by USDA-ARS WA using real-time quantitative PCR and terminal restriction fragment length polymorphism analysis. There was no significant effect of previous crop on the growth and yield response of strawberries irrespective of the disease management strategy used . However, when averaged across all previous crop treatments yields were highest in the ASD treatment with RB+MSM as the carbon source and ASD with RB only . This was likely due to a combination of enhanced fertility in the early season and disease suppression in the later season. Indeed disease severity was significantly reduced with the ASD treatments . What is particularly inTheresting, however, is that the numbers of V. dahliae microsclerotia present in the soil were still lower in the ASD treatments almost 2 years later . This is despite a cover crop being grown and incorporated and a lettuce crop produced in the interim, and suggests a long term suppression of disease by the ASD treatment. This agrees with observations by Goud et al. that ASD provided long term suppression of V. dahliae, but in their case the soil was undisturbed during the intervening 3 years. As discussed below, microbial community changes associated with ASD have been found to persist for many months and may be responsible for the longer term suppression. Excellent anaerobic conditions were created in this field demonstration , in both the organic and conventional fields and were associated with excellent strawberry yields . Previous work found that around 50,000 mV h below 200 mV was necessary for good control of V. dahliaand this threshold was greatly exceeded in both fields. In the conventional fields yields were equivalent to the adjacent fumigated areas, and in both cases there was little or no additional yield benefit from adding pre-plant fertilizer. Rice bran and MSM both contain large amounts of nutrients which can substitute for preplant fertilizer, however, current work is focusing on either reduced rates of application or alternative carbon sources to avoid potential excess losses of nutrients into the environment. Treatments connected by a line are not significantly different at p<0.05 . Main plot treatments are previous crop: fallow, broccoli or cauliflower; and sub plots: ASD=ASD 20 t ha-1 rice bran, ASD+MC=ASD 16.9 t ha-1 rice bran + 3.4 t ha-1 mustard seed meal, MC=3.4 t ha-1 mustard seed meal, UTC = untreated control. Macrophomina phaseolina is present at this location and is a serious concern for strawberry production. In both years of the demonstration ASD greatly improved crops yields relative to the grower’s standard practice and reduced disease severity as measured by crop mortality . The second year trial again demonstrated that no pre-plant fertilizer was necessary at ASD RB 20 t ha-1 plot. There was a significant shift in fungal community composition in soils post ASD, relative to the MSM and the grower standard . However, prior to treatment the following year and after an intervening wheat cover crop, the ASD RB9 treatment still clus.

Thered together and were distinct from the other plots again indicating longer term changes in the soil following ASD. Following the second year with ASD treatment soil fungal communities again showed very distinct clustering based on treatment . This pattern has been observed in other field trials and we are in the process of identifying which species become more prevalent following ASD and if this is related to type of carbon source. Initial screening of NextGen sequencing data suggest that enhanced strawberry yields in response to ASD conducted using rice bran was associated with elevated detection of sequences representing various genera within the Flavobacteria known to have anti-fungal properties. In this opinion-based article, we discuss how indirect effects of drought may adversely affect both the performance of systemic insecticides and also lead to increased risk of insect pests developing behavioral insecticide resistance. Furthermore, we argue that the possible adverse effects of drought on the performance of systemic insecticides has to be given increased research attention, as climate change will likely lead to increased severity and frequency of drought in many agricultural regions. The Food and Agriculture Organization of the United Nations defines a pesticide as “Any substance or mixture of substances intended for preventing, destroying, or controlling any pest … The term includes substances intended for use as a plant growth regulator, defoliant, desiccant, or agent for thinning fruit or preventing the premature fall of fruit.” . Systemic insecticides are chemicals absorbed by plants and distributed internally via the vascular system, delivering the insecticide to untreated plant tissues .

California has the largest and most complex agricultural labor market in the United States, reflecting seasonal employment demands, the predominance of immigrant workers and the significant role of labor contractors in matching workers and jobs. Whether measured in sales, production or acres, California agriculture expanded in the 1990s . Farm sales reached $27 billion in 2000, with about 77 million tons of crops produced on 8.8 million acres. More than half of these sales were in fruits and nuts, vegetables and melons, and horticultural specialties , such as flowers and nursery products. Rising yields meant that more tons of vegetables were produced from the same acreage, while acreage of fruits and nuts rose from 2 million acres in 1990 to 2.4 million acres in 2000, a 19% increase over the 1990s. Many FVH commodities are labor intensive, with labor accounting for 15% to 35% of production costs. Most of the workers employed on FVH farms are immigrants from Mexico, and a significant percentage are believed to be unauthorized . In recent years, several proposals have aimed to reduce unauthorized worker employment in agriculture . In September 2001, Mexican President Vincente Fox called for a U.S.-Mexico labor migration agreement so that “there are no Mexicans who have not entered this country [U.S.] legally, and that those Mexicans who come into the country do so with proper documents. Regularization does not mean rewarding those who break the law. Regularization means that we give legal rights to people who are already contributing to this great nation.” President George Bush agreed: “When we find willing employer and willing employee,plastic pot manufacturers we ought to match the two. We ought to make it easier for people who want to employ somebody, who are looking for workers, to be able to hire people who want to work” .

The United States and Mexico appeared close to agreement on a program to legalize farm and other workers before September 11, 2001. However, after the war on terror was declared, the momentum for a newguest-worker program and the legalization of immigrants already in the country slowed. In summer 2003, there were several new proposals for a migration agreement with Mexico to legalize the status of currently unauthorized workers and allow some to earn immigrant status by working and paying taxes in the United States. There is little agreement, however, on what impacts such a program would have on California’s farm labor market. We used a unique database to examine farm employment trends in California agriculture. The data suggests that: about three individuals are employed for each year-round equivalent job, helping to explain low farm worker earnings; there was a shift in the 1990s from crop farmers hiring workers directly to farmers hiring via farm labor contractors ; and there is considerable potential to improve farm labor market efficiency, by using a smaller total workforce with each worker employed more hours and achieving higher earnings.California employers who pay $100 or more in quarterly wages are required to obtain an unemployment insurance reporting number from the California Employment Development Department . The EDD then assigns each employer or reporting unit a four-digit Standard Industrial Classification or, since 2001, a six-digit North American Industry Classification System code that reflects the employer’s major activity . Major activities are grouped in increasing levels of detail; for example, agriculture, forestry and fisheries are classified as a major industrial sector and, within this sector, SIC 01 is assigned to crops, 017 to fruits and nuts and 0172 to grapes. We defined “farm workers” as unique Social Security numbers reported by farm employers to the EDD, and then summed their California jobs and earnings. This enabled us to answer questions such as how many farm and non-farm jobs were associated with a particular SSN or individual in 1 year, and in which commodity or county a person had maximum earnings.

We adjusted the raw data before doing the analysis. Farm employers have reported their employees and earnings each quarter since 1978, when near universal UI coverage was extended to agriculture. Although it is sometimes alleged that farm employers, especially FLCs, do not report all their workers or earnings, there is no evidence that under reporting of employees or earnings is more common in agriculture than in other industries that hire large numbers of seasonal workers, such as construction. We excluded from the analysis SSNs reported by 50 or more employers in 1 year . We also excluded wage records or jobs that had less than $1 in earnings and jobs, or that reported earnings of more than $75,000 in one quarter. These adjustments eliminated from the analysis 2,750 SSNs, 62,571 wage records or jobs and $803 million in earnings. These exclusions were about 0.25%, 2.7% and 6.1% of the totals, respectively, and are documented more fully in Khan et al. . There is no single explanation for the outlier data we excluded. In some cases, several workers may share one SSN, while in others our suspicion that a SSN had “too many” jobs may represent data-entry errors. During the 1990s, the Social Security Administration cleaned up SSNs, including threatening to fine and reject tax payments from employers with too many mismatches between SSNs and the names associated with those SSNs, which should have reduced the number of SSNs reported by employers. We think the rising number of SSNs reflects more individuals employed in agriculture, not more noise in the data.Agricultural employment can be measured in three major ways: at a point in time, as an average over time or by counting the total number of individuals employed over some period of time.If 100 workers are employed during each month and there is no worker turnover from month to month, then point in time, average and total employment is 100. However, agricultural employment during the six summer months may be 150, versus 50 during the six winter months, meaning that point, average and total employment counts differ.

We began with all SSNs reported by agricultural employers , summed the jobs and earnings of these SSNs within each SIC code, and assigned each SSN to the four-digit SIC code in which the worker had the highest earnings. This means that a SSN reported by a grape employer as well as by an FLC would be considered a grape worker if his highest-earning job was in grapes. Farm workers had a total of 1.5 million farm jobs in 1991, 1.7 million in 1996 and 1.8 million in 2001. One-quarter also had at least one non-farm job — about 407,000 workers were both farm and non-farm workers in 1991, 453,000 in 1996 and 697,000 in 2001 . The total California earnings of persons employed in agriculture were $11.1 billion in 1991, $12.0 billion in 1996 and $15.8 billion in 2001 . The share of total earnings for farm workers from agricultural employers was 77% in 1991, 77% in 1996 and 71% in 2001, indicating that in the late 1990s,black plastic plant pots wholesale farm workers tended to increase their supplemental earnings via non-agricultural jobs. Average earnings per job were highest in livestock, $13,800 per job in 2001. There was little difference between average earnings per job in agricultural services and crops . Average earnings per job were higher for the non-farm jobs of agriculture workers than for agriculture jobs .In 2001, California’s farm workers held 2.5 million jobs, including 1.8 million jobs with agricultural employers. These agricultural jobs included 630,000 in crops, 69,000 in livestock and 1.1 million in agricultural services. The agricultural services sector includes both farm and non-farm activities, such as veterinary and lawn and garden services; FLCs accounted for 70% of the employees reported by farm agricultural services. Fruits and nuts accounted for 53% of the crop jobs, dairy for 39% of the livestock jobs and FLCs for 58% of the agricultural services jobs. The major change between 1991 and 2001 was the drop of 54,000 jobs in crop production and increase of 313,000 jobs in agricultural services. We placed SSNs in the detailed commodity or SIC code that reflected the maximum reported earnings for the worker, and considered workers to be primarily employed in the SIC with maximum earnings. In 2001, there were 877,000 primary farm workers, and they included 322,000 reported by crop employers, 50,000 reported by livestock employers and 504,000 reported by agricultural service employers. Fruit and nut employers accounted for 47% of the crop-reported workers, dairy for 40% of the livestock-reported workers and FLCs for 44% of the agricultural services–reported workers. The major change between 1991 and 2001 was the increase in number of SSNs with their primary job in agriculture — from 758,000 to 877,000. There was a slight drop in the number of workers reported by crop employers, a slight increase in livestock workers and a sharp 135,000 increase in agricultural services workers, anchored by a 59,000 increase in workers reported by FLCs in 2001. Most farm workers had only one job. In 2001, 53% of the SSNs were reported by only one employer to the EDD, 26% were reported twice, 12% three times, 5% four times and 4% five or more times.

During the 1990s, about 65% of farm workers were reported by one agricultural employer only, 17% to 21% by two agricultural employers, 5% by at least two agricultural employers and one non-farm employer, and 9% to 12% by one farm and one non-farm employer. In the three-digit SIC codes representing more detailed commodity sectors, 60% to 83% of the employees had only one job. For example, in 2001 79% of the employees reported by dairy farms had one dairy farm job, while 7% also had a second agricultural job — 3% had a dairy job, a second farm job and a non-farm job, and 11% had a non-farm job in addition to the dairy job. About two-thirds of the employees of FLCs and farm management companies had only jobs with one such employer; 22% had another farm job; 6% had an FLC job, another farm job and a non-farm job; and 6% had a non-farm job in addition to the FLC job. Even more detailed four-digit SIC codes showed the same pattern: the commodities or SICs most likely to offer year-round jobs such as dairies and mushrooms had 70% to 80% of employees working only in that commodity, while commodities or SICs offering more seasonal jobs, such as deciduous tree fruits and FLCs, had 53% to 63% of employees working only in that commodity. At the four-digit, SIC-code level, the five largest SICs accounted for about 45% of the agricultural wages reported.Agricultural employers paid a total of $11 billion in wages in 2001, an average of $10,200 per worker . Earnings were highest for the 64,000 workers primarily employed in livestock; they averaged $14,800, followed by those primarily employed by crop employers and those employed by agricultural farm services, custom harvesters and FLCs . There was considerable variation in earnings among workers in agricultural farm services: workers in soil preparation services averaged $21,100 in 2001, versus $12,700 for crop preparation services for market and $4,400 for FLC employees. The average earnings of primarily farm workers varied significantly, even within detailed four-digit SIC codes — in most cases, the standard deviation exceeded the mean wage . Median earnings were generally less than mean earnings, reflecting that higher wage supervisors and farm managers pulled up the mean. If the workers in detailed commodities are ranked from lowest-to-highest paid, the lowest 25% of earners in an SIC category generally earned less than $4,000 a year. For example, among workers primarily employed in vegetables and melons in 2001 , the first quartile or 25th percentile of annual earnings was $3,000. This reflects relatively few hours of work — if these workers earned the state’s minimum wage of $6.25 an hour in 2001, they worked 480 hours. The 25th percentile earnings cutoff was lowest for those employed primarily by FLCs, only $634, suggesting that FLC employees receiving the minimum wage worked 101 hours. The highest 25th percentile mark was in mushrooms , $9,491, which reflects 1,519 hours at minimum wage. The 75th percentile marks the highest earnings that a non-supervisory worker could normally expect to achieve — 75% of workers reported earning less than this amount and 25% earned more.

Five hotpots were found in chloroplast genome of Veroniceae , and two universal marker, trnH-psbA and matK were identified, respectively. Then highly variable regions were selected as potential molecular markers for Fritillaria, including ycf1, which was also selected in this study. Sequences of these variable regions founded in this study could be regarded as potential molecular markers for species identification and evolutionary studies and have been shown to be valuable for studies in other groups.Oligonucleotide repeats play an important role for generating indels, inversion and substitutions. Repeat sequences in the chloroplast genome could provide valuable information for understanding not only the sequence divergence but the evolutionary history of the plants. We have detected five types of large repeats in the seven Pulsatilla cp genomes. Among them, the most common repeat types are forward and palindromic repeats, followed by reverse repeats, and only little complement repeats were found in Pulsatilla cp genomes . Most of the repeats were short, ranging from 30–49 bp . We also identified multiple microsatellite repeats, also known as simple sequence repeats or short tandem repeats. Due to their codominant inheritance and high variability, SSRs are robust and effective markers for species identification and population genetic analyses. Most of the mononucleotide repeats were composed of A/T. The other microsatellites types were also dominated by AT/TA, with very little G/C . In this study, plentiful microsatellite loci were found through the comparative analysis of Pulsatilla cp genome sequences. In total,raspberry grow in pots we detected six types of microsatellite based on the comparison of seven Pulsatilla cp genomes . Each Pulsatilla cp genome had 69–87 microsatellites. The lengths of repeat motifs of these microsatellites ranged from 10 to 21 bp .

Among the four structural regions in the cp genomes, most of the repeats and microsatellites were distributed in LSC, followed by SSC, and fewest in IRa/IRb , which were also reported in other studies in angiosperms. These SSRs and repeat sequences are uncorrelated with genome size and phylogenetic position of the species, but will provide important information for further studies of phylogenetic reconstruction and infra- and inter-specifc genetic diversity.Chloroplast genomes have been widely used and have made significant contributions to phylogeny reconstruction at different taxonomic levels in plants. To better clarify the evolutionary relationships within Pulsatilla, we used each data set to construct phylogenetic trees using the ML analytical methods. We also construct phylogenetic trees with those eight highly variable regions using the ML, MP analytical methods. All tree topology structures were identical. Therefore, here we presented the phylogenetic studies using the ML tree with the support values from the MP analyses recorded at the corresponding nodes . The phylogenetic tree based on all data sets from the complete plastid genome sequences yielded the same topology. The phylogenetic tree based on chloroplast genome differed from that of the DNA barcode combination rbcL+matK+trnH-psbA, but with higher support values. The phylogenetic trees based on data from complete plastid genome sequences showed that the species of Pulsatilla formed a monophyletic group which in turn includes two strongly supported clades. One clade comprised P. alpina and P. occidentalis, members of subg. Preonanthus. The other comprised two subclades: members of P. hirsutissima, P. ludoviciana, P. multifdi, P. patens and P. vernalis, and species of P. chinensis, P. dahurica, P. grandis and P. pratensis. All the species of the two subclades are members of the subg. Pulsatilla. These results were congruent with our former results based on universal markers.

In phylogenetic analyses, compared to the combination of barcodes, the full chloroplast genome sequence data formed distinct clades with high bootstrap support, improving the inadequate resolution of barcodes combination. The LSC regions and coding regions have the same topology structures with robust support. However, sequencing of genomic DNA is still expensive. It is necessary to utilize variation within chloroplast regions for rapid species-specific assay. Here we found that phylogenetic inference based on highly variable regions yielded a tree with the same topology as the one recovered based on complete chloroplast genome sequences, demonstrating the high utility of hot spots of variability for species identification and phylogenetic analysis. More samples and laboratory works are needed in the future to increase the number of these variable regions available for study.High frequency irrigation systems involve fastidious planning and complex designs, so that timely and accurate additions of water and fertilizer can result in sustainable irrigation. At the same time these production systems are becoming more intensive, in an effort to optimise the return on expensive and scarce resources such as water and nutrients. Advanced fertigation systems combine drip irrigation and fertilizer application to deliver water and nutrients directly to the roots of crops, with the aim of synchronising the applications with crop demands , and maintaining the desired concentration and distribution of ions and water in the soil . Hence a clear understanding of water dynamics in the soil is important for the design, operation, and management of irrigation and fertigation under drip irrigation . However, there is a need to evaluate the performance of these systems, because considerable localised leaching canoccurnear the driplines, evenunderdeficitirrigation conditions .

The loss of nutrients, particularly nitrogen, from irrigation systems can be expensive and pose a serious threat to receiving water bodies . Citrus is one of the important horticultural crops being grown under advanced fertigation systems in Australia. Fertigation delivers nutrients in a soluble form with irrigation water directly into the root-zone, thus providing ideal conditions for rapid uptake of water and nutrients. Scholberg et al. demonstrated that more frequent applications of a dilute N solution to citrus seedlings doubled nitrogen uptake efficiency compared with less frequent applications of a more concentrated nutrient solution. Delivery of N through fertigation reduces N losses in the soil-plant system by ammonia volatilisation and nitrate leaching . However, poor irrigation management, i.e., an application of water in excess of crop requirements, plus the storage capacity of the soil within the rooting depth, can contribute to leaching of water and nutrients below the root zone. Therefore, optimal irrigation scheduling is important to maximise the uptake efficiencies of water and nutrients . Most of the citrus production along the Murray River corridor is on sandy soils, which are highly vulnerable to rapid leaching of water and nutrients. Nitrogen is the key limiting nutrient and is therefore a main component of fertigation. An increasing use of nitrogenous fertilizers and their subsequent leaching as nitrate from the root zone of cropping systems is recognised as a potential source of groundwater contamination,30 planter pot because the harvested crop seldom takes up more than 25–70% of the total applied fertilizer . Several researchers have reported substantial leaching of applied N under citrus cultivation in field conditions . Similarly, in lysimeter experiments, Boaretto et al. showed 36% recovery of applied nitrogen by orange trees, while Jiang and Xia reported N leaching of 70% of the initial N value, and found denitrification and leaching to be the main processes for the loss of N. These studies suggest that knowledge of the nitrogen balance in cropping systems is essential for designing and managing drip irrigation systems and achieving high efficiency of N fertilizer use, thereby limiting the export of this nutrient as a pollutant to downstream water systems. Quantifying water and nitrogen losses below the root zone is highly challenging due to uncertainties associated with estimating drainage fluxes and solute concentrations in the leachate, even under well-controlled experimental conditions . Moreover, direct field measurements of simultaneous migration of water and nitrogen under drip irrigation is laborious, time-consuming and expensive . Hence simulation models have become valuable research tools for studying the complex and interactive processes of water and solute transport through the soil profile, as well as the effects of management practices on crop yields and on the environment . In fact, models have proved to be particularly useful for describing and predicting transport processes, simulating conditions which are economically or technically impossible to carry out in field experiments . Several models have been developed to simulate flow and transport processes, nutrient uptake and biological transformations of nutrients in the soil .

HYDRUS 2D/3D has been used extensively for evaluating the effects of soil hydraulic properties, soil layering, dripper discharge rates, irrigation frequency and quality, timing of nutrient applications on wetting patterns and solute distribution because it has the capability to analyse water flow and nutrient transport in multiple spatial dimensions . In the absence of experimental data we can use multidimensional models solving water flow and nutrient transport equations to evaluate the multi-dimensional aspect of nitrate movement under fertigation . However, earlier simulation studies have reported contradictory results on nitrate distribution in soils. For example, Cote et al. reported that nitrate application at the beginning of an irrigation cycle reduced the risk of leaching compared to fertigation at the end of the irrigation cycle. On the other hand, Hanson et al. reported that fertigation at the end of an irrigation cycle resulted in a higher nitrogen use efficiency compared to fertigation at the beginning or middle of an irrigation cycle. These studies very well outlined the importance of numerical modelling in the design and management of irrigation and fertigation systems, especially when there is a lack of experimental data on nutrient transport in soils. However, there is still a need to verify the fate of nitrate in soils with horticultural crops and modern irrigation systems. Therefore, a lysimeter was established to observe water movement and drainage under drip irrigated navel orange, and to calibrate the HYDRUS 2D/3D model against collected experimental data. The model was then used, in the absence of experimental data on nitrate, to develop various modelling scenarios to assess the fate of nitrate for different irrigation and fertigation schemes.The study was conducted on a weighing lysimeter assembled and installed at the Loxton Research Centre of the South Australian Research and Development Institute. The lysimeter consisted of a PVC tank located on 1.2 m × 1.2 m pallet scales fitted with 4 × 1 tonne load-cells, and connected to a computerised logging system which logged readings hourly. A specially designed drainage system placed at the bottom of the lysimeter consisted of radially running drainage pipes, which were connected to a pair of parallel pipes, which facilitated a rapid exit of drainage water from the lysimeter . These pipes were covered in a drainage sock and buried in a 25-cmlayer of coarse washed river sand at the base of the lysimeter, which ensured easy flushing of water through the drainage pipe. A layer of geo-textile material was placed over the top of the sand layer to prevent roots growing down into it, as this layer was intended to be only a drainage layer. A healthy young citrus tree was excavated from an orchard at the Loxton Research Centre and transplanted into the lysimeter. A soil profile approximately 85 cm deep was transferred to the tank with the tree and saturated to remove air pockets and to facilitate settling. The final soil surface was around 10 cm below the rim of the tank. Soil samples were collected from0 to 20, 20 to 40, 40 to 60, 60 to 85, and 85 to 110 cm depths to measure bulk density and to carry out particle size analysis. Two months after transplanting, the lysimeter was installed amongst existing trees in the orchard. Measurements were initiated after about six months, in order to enable the plant to adjust to the lysimeter conditions. The lysimeter was equipped with Sentek® EnviroSCAN® logging capacitance soil water sensors installed adjacent to the drip line at depths of 10, 20, 40, 60, and 80 cm to measure changes in the volumetric soil water content.The experimental site was approximately 240 m from an established weather station, which measured air temperature, relative humidity, wind speed , rainfall, and net radiation.Irrigation was applied using 3 pressure compensated emitters with a discharge rate of 4 L h−1. Emitters were located on a circle 25 cm away from the tree trunk at an equal distance from each other . The irrigation schedule was based on the average reference evapotranspiration during the last 10 years at the site, multiplied by the crop coefficient taken from Sluggett .

Delayed sleep onsets may be due to a phase-delay of the circadian pacemaker controlling sleep onset, an acute effect of evening light on alertness or both. Additional studies designed to measure circadian phase physiologically are required to address this. In either case, the results support a hypothesis that exposure to artificial light after sunset can delay sleep onset and reduce sleep duration. Such effects can be expected to increase as access to electricity on Tanna Island expands. Historical writings have been taken to suggest that in pre-industrial western European populations, nocturnal sleep habitually occurred in two bouts – so-called ‘first and second sleep’ – separated by an hour or more of midnight waking. Segmented patterns suggestive of ‘first and second sleep’ have been observed in a small-scale agricultural society in Madagascar. In the present study, 14% of the 519 recorded nights exhibited a bout of nocturnal waking that was sufficient for the state detection algorithm to score two separate bouts of sleep. However, this pattern does not appear to ft with the concept of ‘first and second sleep’ as a reliable sleep phenotype. About 50% of the subjects showed evidence of split sleep, and among those that did, the pattern was sporadic, with split sleep typically evident on only one of up to eight nights of recording. Splits also occurred at variable times of night. Nocturnal sleep in the indigenous residents of Tanna Island is therefore best described as monophasic, with occasional opportunistic daytime naps. An increase in the number of sleepers sharing the same sleep surface or room can reduce sleep efficiency or duration. Te number of co-sleepers was slightly greater in the non-electric communities,raspberry container size but sleep duration and efficiency were lower in the electric communities. Also, there was no association between the number of co-sleepers and sleep duration and efficiency in either community.

In addition, residents of Tanna commonly sleep on hard surfaces, which would not transfer movement between adjacent co-sleepers. For these reasons, it is unlikely that any differences in the number of co-sleepers would account for differences in sleep duration and efficiency between communities.Although the range of ages was limited in the present sample , a negative relationship with age and sleep efficiency did emerge, but only in non-electric communities. In communities with an electric grid, the lack of a relationship indicated that young adults also exhibited lower sleep efficiency, something that was not apparent in the young adults of the non-electric communities. A non-electric Haitian population showing lower sleep efficiency in younger adults suggests lifestyle factors, such as, increased childcare responsibilities, nocturnal household duties, or engagement in social activities that mask physiological age differences, all of which may be more easily facilitated in Tanna’s electric communities. On Tanna Island, males are often up late drinking kava, which is an important custom in Vanuatu, as the nakamal, where kava is consumed, is an important gathering place for older men to pass along knowledge and advice to young males in the village. Kava is mildly sedating, but males and non-breastfeeding females pooled separately across communities did not exhibit difference in sleep duration or efficiency, suggesting minimal effect of Kava consumption on sleep. We do not have sufficient information to be able to separate and compare sleep on nights with and without Kava consumption, and any effects might not be detectable by actigraphy. A limitation of this study is that data were collected only in April and May, during the transition from summer to winter, when daylength averages ~11.5 h. Seasonal variation in sleep timing has been reported in traditional hunter-gatherer societies, with daily wake-up time in one study population tracking seasonal changes in the time of the daily minimum of environmental temperature more closely than changes in the time of sunrise. In the present study, temperature recorded in representative sleeping huts showed a daily minimum that occurred on average 26min after sunrise, in both the coastal and the inland villages. Wake onsets on average were closer to sunrise than to the ambient temperature minimum in both groups. Ambient temperature may be less significant for sleep timing on Tanna Island because nights are milder, the daily temperature range is modest , and the transition from decreasing to increasing temperature is gradual.

Also, temperature is mild throughout the year and seasonal variation is modest. In this respect, the natural sleep environment on Tanna Island may be more similar to modern built sleep environments, in which temperature changes from day to night are minimized. If ambient temperature plays a role in sleep timing, then we would not expect to see a large effect of seasonal temperature changes on sleep parameters in residents of Tanna Island. The results of this study indicate that sleep measured by actigraphy in the small-scale traditional society on Tanna Island can be differentiated from sleep in western industrialized samples by relatively long duration and low efficiency. Availability of on-demand electric light appears to have a detectable effect on nocturnal sleep onset and duration, but this effect is likely mitigated by exposure to natural light throughout the day. Actigraphy studies of indigenous Ni-Vanuatu living in industrialized population centers elsewhere in Vanuatu may provide further insight into how lifestyle and industrialization shape sleep.Decades of both theoretical and empirical research based on the polygyny threshold model have suggested that polygyny should be more common and more pronounced in populations in which males differ substantially in resource control. In humans, this will be in socio-cultural contexts where wealth is held predominately by men, and where there is high inequality in its distribution. Historical and cross-cultural records, however, suggest that polygyny became less common as relatively egalitarian horticultural production systems transitioned into agricultural production systems, in spite of the fact that agriculture is characterized by both a greater importance of material wealth in the production process and greater levels of material wealth inequality than horticulture. This is the polygyny paradox. Existing hypotheses for the rise of monogamy with historic agricultural populations invoke the increasing importance of rival1 material wealth among agriculturalists, inheritance rules in conjunction with paternity certainty, male power relations, declines in female contributions to production, pathogen risk and punishment and cultural group selection via the imposition of norms.

Since human behavioural variation is often determined by many underlying factors, there are likely to be complementary effects among the potential causes identified in these hypotheses. Specifically, there should be coevolutionary interactions between the individual-level, economic- and fitness-based explanations for the rise of monogamy advanced here, and the cultural evolutionary explanations provided by Henrich et al. and Bauch & McElreath. Our results show how individual fitness maximization can explain the de novo origins of predominant monogamy within highly unequal populations. Should monogamy have group-level fitness benefits as suggested by Henrich et al., its emergence in specific groups via the mechanism we propose would provide the source populations for cultural group selection dynamics to propagate monogamy to other populations. Explanations for the rise of monogamy in agricultural societies in the spirit of Alexander and Henrich et al. develop the idea that powerful leaders might have imposed monogamy on the masses because such a marriage norm leads to greater in-group male–male cooperation,raspberry plant container improving the success of the group in inter-group contests. The economically grounded explanation for the rise of monogamy that we present here is not necessarily in competition with such theories. Our model, however, establishes that basic changes in the structuring of wealth inequality coinciding with the rise of class-based societies would have made monogamy adaptive at the individual level in a large fraction of the population—greatly increasing the scope for hypotheses advancing hierarchical imposition or even frequency dependent social transmission of norms for monogamy. The present analysis builds on work recognizing the importance of inherited wealth in structuring family relationships. To this existing literature, we introduce a new individual-level, cross-cultural dataset of wealth, marriage and reproductive outcomes, numbering 11 813 records from 29 human populations, including hunter –gathers, horticulturalists, agropastoralists and agriculturalists. Our dataset is unusual in both its scope and in the availability of individual-level information, rather than qualitative societal summaries. While not without its limitations—discussed in more detail throughout—it captures the core features of the polygyny paradox. Following Oh et al. , we develop a model of the equilibrium fraction of women married polygynously in a population where the extent of polygyny is determined by the fitness maximizing choices of both men and women. In contrast to the standard polygyny threshold model, which is a one-sided mate choice model that allows only for female choice, we develop a mutual or two-sided model. In this model, male choice refers not to selecting particular females on the basis of their quality , but rather to the male’s choice of the number of wives that will maximize his fitness. A male’s demand for wives depends on his level of wealth and the costs of mating investment, and can be more than, less than or equal to the total number of women who would choose to marry him. Mutual mate choice is rare in nature, but the conditions for it are met in species in which biparental care is important for the survival of offspring, as is typically true of humans.

From our theoretical model, we identify two conditions that jointly can lead to a decrease in the population-level frequency of polygyny in highly unequal agricultural populations: in these highly stratified economies, the fraction of men with sufficient wealth to make polygynous marriage an attractive option for them and their potential partners is low relative to other subsistence systems, and decreasing marginal fitness returns to increasing number of wives above and beyond the fitness costs of sharing a husband’s wealth sharply limit the number of wives acquired by exceptionally wealthy individuals. We use our empirical data to demonstrate that the transition to agriculture is associated with both of these factors identified as drivers of monogamy.The Standard Cross-Cultural Sample illustrates that the frequency of polygyny is relatively high in horticultural and pastoral populations, and low in agricultural populations. These findings are robust to use of quantitative or qualitative descriptors of polygyny. The third panel presents our estimates of the extent of material wealth inequality among males in the four production systems. Theoretical models of mating systems predict that polygyny should be positively associated with inequality in male resources, and more specifically with what Murdock terms ‘movable property or wealth which can be accumulated in quantity by men’. These forms of rival material wealth are, as we have just seen, more unequally held in horticultural economies than among foragers, which is consistent with the greater extent of polygyny in the former.Oh et al. show that inequality in reproductively important, non-rival forms of wealth—network ties, genes conferring adaptive phenotypes or acquired knowledge, for example— can also be a strong driver of polygyny, contributing to the explanation of substantial levels of polygyny in some societies with little rival wealth inequality. Indeed, there is empirical evidence that non-rival forms of wealth are associated with polygynyous marriage in some foraging and horticultural populations. While the polygyny threshold model has been effective in predicting the distribution of polygynous males within populations , the reduced level of polygyny in agricultural populations typically characterized by greater inequality poses a serious challenge to existing models of mating and marriage.To address this challenge, we build a comparative database of individual-level wealth, marriage and reproductive success measures in 29 diverse populations distributed over a wide geographical range . Table 1 provides population-specific background data. In order to use all cohorts of the adult male populations, relevant measures—wives and wealth proxies—are age adjusted in a Bayesian framework to represent their predicted values at age 60. This method of age adjustment assumes that the additional acquisition of wives and wealth from the time of censor to the age of 60 are unmeasured positive random variables, with mean values governed by the remaining time for acquisition and the age-specific acquisition rate trajectories inferred from the population cross sections . Our polygyny measures reflect the per cent of women who will ever be married to a man who marries more than once—in other words, in contrast to the data in figure 1a, we consider sequential marriage as a form of polygyny since the offspring of each mother are rival claimants to a father’s property.

For 186 of the 2320 species examined here, the cross-validated MAE produced by the phenological model was identical to that estimated using the collection dates of the specimens alone . Although these species were retained for use in PhenoForecaster, it should be noted that no climate data may be entered for these species, and the resulting predictions of flowering time consist only of a constant value reflecting an estimate of the mean observed flowering date for that species, which is not influenced by local climate conditions. Additional species will be added and models will be updated as new data or superior modeling techniques become available.Although many studies have examined patterns of phenological variation in response to local climate, few tools exist for the prediction of phenological timing under novel climate conditions. PhenoForecaster provides a free, quick, and easy-to-use software package that allows researchers of any background to quickly predict the mean flowering date of angiosperm species under novel annual conditions, or at locations where the phenology of that species has not previously been observed. Its intuitive user interface and compatibility with existing spatial climate estimation packages such as ClimateNA make phenological prediction easy to accomplish by researchers of any background without the need for extensive training or familiarity with phenoclimate modeling. It should be noted, however, that the accuracy of predictions by PhenoForecaster is variable and depends highly on the species selected for prediction. The expected accuracy of PhenoForecaster output, as reflected by the MAE value for that species, should be kept in mind when dealing with predicted MFD values generated by PhenoForecaster. Furthermore,blueberry plant size these models do not account for potential heterogeneity of phenological responsiveness among populations of a given species, but instead represent mean phenological responsiveness across all available specimens for each species.

These data were also based on models trained using phenological observations throughout North America only, and using derived estimates of local climate condition produced using ClimateNA; these estimates may exhibit some differences from ground-based observations of these climate parameters, or from estimates of these climate parameters derived using different methods. Thus, predictions of the phenology of these species outside of North America, or based on different sources of climate data, should be treated with caution. In addition, it should be remembered that PhenoForecaster models the timing of MFD only, and that the relationship of MFD to other phenophases, such as leaf-out, date of first flower, or date of last flower, may be highly variable among species and across climate gradients. These predictions should therefore be treated as dates on which the individuals of a given species are likely to be in flower where they have experienced a particular suite of climatic conditions, rather than as the onset or termination date of any specific phenophase. Where possible, we also recommend cross-checking predicted MFD values generated by PhenoForecaster against observed MFD values for that species, particularly when evaluating the phenology of a species under conditions that are outside of its historical range limits. Nevertheless, PhenoForecaster represents a freely available and powerful tool that allows any researcher to conduct rapid predictions of phenological timing under past, projected, or otherwise novel climate conditions.Many agricultural robots have been developed to perform precision farming operations and replace or augment humans in certain tasks. These robots come in two main types: I) self-propelled mobile robots, and II) robotic “smart” implements that are carried by a vehicle. Type-I robots span wide ranges of sizes and designs. Conventional agricultural self-propelled machines such as tractors, sprayers, and combine harvesters have been “robotized” over the last decade through the introduction of GPS/GNSS auto-guidance systems. These machines are commercially available today and constitute the large majority of “agricultural robots”.

They can drive autonomously in parallel rows inside fields while a human operator supervises and performs cultivation-related tasks; turn autonomously at field headlands to enter the next row; and coordinate their operations. Autonomous cabinless general purpose ‘tractor robots’ were recently introduced by several companies that are compatible with standard cultivation implements. These larger robots are designed primarily for arable farming related operations that require higher power and throughput, such as ploughing, multi-row seeding, fertilizing, and spraying, harvesting and transporting. A large number of smaller type-I special purpose mobile robots have also been introduced for lower-power applications such as scouting and weeding of a smaller number of rows at a time. Most of these robots are research prototypes introduced by various research groups. A few commercial or near-commercial mobile robots have emerged in applications like container handling in nurseries and seeding , respectively. Small robots like Xaver are envisioned to operate in teams and are an example of a proposed paradigm shift in the agricultural machinery industry, which is to utilize teams of small lightweight robots to replace large and heavy machines, primarily to reduce soil compaction.Recent review articles have discussed some of the opportunities and challenges for agricultural robots and analyzed their functional sub-systems ; summarized reported research grouped by application type and suggested performance measures for evaluation ; and presented a large number of examples of applications of robotics in the agricultural and forestry domains and highlighted existing challenges . The goals of this article are to: 1) highlight the distinctive issues, requirements and challenges that operating in agricultural production environments imposes on the navigation, sensing and actuation functions of agricultural robots; 2) present existing approaches for implementing these functions on agricultural robots and their relationships with methods from other areas such as field or service robotics; 3) identify limitations of these approaches and discuss possible future directions for overcoming them. The rest of the article is organized as follows.

The next section discusses autonomous navigation , as it is the cornerstone capability for many agricultural robotics tasks. Afterwards, sensing relating to crop and growing environment is discussed, where the focus is on assessing information about the crop and its environment in order to act upon it. Finally, interaction with the crop and its environment is discussed, followed by summary and conclusions. The operation computes a complete spatial coverage of the field with geometric primitives that are compatible with and sufficient for the task, and optimal in some sense. Headland space for maneuvering must also be generated. Agricultural fields can have complex, non-convex shapes, with non-cultivated pieces of land inside them. Fields of complex geometry should not be traversed with a single orientation; the efficiency would be too low because of excessive turning. Also,plant raspberry in container fields are not necessarily polygonal, they may have curved boundaries and may not be flat. Additionally, most agricultural machines are nonholonomic and may carry a trailer/implement, which makes computing turning cost between swaths non trivial . Finally, agricultural fields are not always flat and field traversal must take into account slope and vehicle stability and constraints such as soil erosion and compaction.Computing a complete spatial coverage of a field with geometric primitives is in principle equivalent to solving an exact cellular decomposition problem .Choset and Pignon, developed the Boustrophedon cellular decomposition . This approach splits the area into polygonal cells that can be covered exactly by linear back-and-forth motions. Since crops are planted in rows, this approach has been adopted by most researchers. A common approach is to split complex fields into simpler convex sub-fields via a line sweeping method, and compute the optimal driving direction and headland arrangement for each sub-field using an appropriate cost function that encodes vehicle maneuvering in obstacle-free headland space . This approach has been extended for 3D terrain .Existing approaches assume that headland space is free of obstacles and block rows are traversed consecutively, i.e., there is no row-skipping. These are simplifying assumption, as it has been shown that proper row sequences reduce total turning time substantially . However, dropping this assumption would require solving a routing optimization problem inside the loop that iterates through driving orientations, and many maneuvering/turning motion planning problems inside each route optimization; this would be very expensive computationally. Furthermore, all algorithms use a swath of fixed width, implicitly assuming that the field will be covered by one machine, or many machines with the same operating width. Relaxing this assumption has not been pursued, but the problem would become much more complicated. Planning could also be extended to non-straight driving patterns using nonlinear boustrophedon decompositions based on Morse functions , with appropriate agronomic, cultivation and machine constraints. Finally, as pointed out by Black more , row cultivation was historically established because it is easier to achieve with animals and simple machines. Crops do better when each plant has equal access to light, water and nutrients. Small robots could grow crops in grid patterns with equal space all around by following arbitrary driving patterns that may be optimal for the cropping system and the terrain. Hence the boustrophedon assumption could be relaxed and approximate cellular decomposition could be used to compute optimal driving patterns, where field shape is approximated by a fine grid of square or hexagonal cells. This approach has received very little attention, as field spatial planning has targeted existing large machines. An example of early work in this direction combined route planning and motion planning, with appropriate agronomic, cultivation and machine constraints .

The basic version of route planning computes an optimal traversal sequence for the field rows that cover the field, for a single auto-guided machine with no capacity constraints. This is applicable to operations in arable land, orchards and greenhouses that do not involve material transfer or, when they do, the quantities involved are smaller than the machine’s tank or storage space; hence the machine’s limited storage capacity does not affect the solution. For operations where the machine must apply or gather material in the field the maximum number of rows it can cover is restricted by its capacity; the same applies to fuel. Hence, route planning with capacity constraints is a more complicated version of the problem. When many machines operate in the same field there are two classes of operations which have different characteristics. The first class is when machines are independent of each other, i.e., they do not share any resources. In such cases, coordinated route planning is straightforward because the machines can simply work on different swaths or sub-fields of the field; possible crossings of their paths at the headlands and potential collisions can be resolved during task execution. The second class is cooperative field operations, also known as in-field logistics, which are executed by one or more primary unit/s performing the main task and one or more service unit/s supporting it/them. For example, in a harvesting operation a self-propelled harvester may be supported by transport wagons used for out-of-the field removal of harvested grain . Similarly, in fertilizing or spraying operations the auto-guided spreader/sprayer may be supported by transport robots carrying the fertilizer/sprayer for the refilling of the application unit. Agricultural tasks are dynamic and stochastic in nature. The major issues with off-line route planning are that it breaks down in case of unexpected events during operations, and it can only be performed if the “demand” of each row is known exactly in advance. For example, if a sprayer’s flow rate is constant or the crop yield is known in advance, the quantity of chemical or harvest yield of each field row can be pre-computed and optimal routing can be determined. However, yield maps are either not available before harvest or their predicted estimates based on sampling or historic data contain uncertainty. Also, robotic precision spraying and fertilizing operations are often performed “on-the go” using sensors, rather than relying on a pre-existing application map. Hence, information is often revealed in a dynamic manner during the execution of the task. Vehicle routing for agricultural vehicles is based on approaches from operations research and transportation science. Optimal row traversal for a single or multiple independent auto-guided vehicles has been modeled and solved as a Vehicle Routing Problem . This methodology was conceptually extended to include multiple identical collaborating capacity-limited machines with time-window constraints, and to nonidentical vehicles . A review of similar problems in transportation science is given in . The problem of visiting a set of known, pre-defined field locations to take measurements or samples is not an area coverage problem, and was recently modeled as an orienteering problem for non-collaborating robots, and as VRP with time windows for capacitated cooperating vehicles .

Almond root stocks have been shown to alter root, shoot, trunk, and fruit development, probably by affecting the allocation of carbon assimilates between these tissues. Khadivi-Khub and Anjam evaluated the Iranian cultivar ‘Rabiee’ grown on P. scopariaand ‘Estahban’ root stock under normal and rainfed conditions. They reported significant differences in tree height, trunk diameter, annual growth, and internode length, observing reduced scion growth when grafted on P. scoparia root stock. P. scoparia, suggesting potential as a dwarfing root stock. Parvaneh et al. evaluated three Iranian cultivars on bitter almond, sweet almond, and peach root stocks and found that cultivars grafted on peach had greater vegetative growth, while scions grown on both bitter and sweet almonds had reduced growth, resulting in smaller trees. The magnitude of the effect varied with cultivar. In a regional root stock trial at California State University, Fresno, significant differences among root stocks were found in canopy growth, tree height, and tree circumference. Almonds grafted on peach root stock had larger scion diameters than on almond root stocks. Preliminary results from a vigor study showed that trunk diameter of the scion cultivar depends on the scion-root stock interaction. The root stock effect differed depending on the cultivar grafted and scion vigor itself. Lordan et al. studied the performance of two Spanish almond cultivars, ‘Marinada’ and ‘Vairo’, grafted onto different root stock genotypes and reporting strong root stock effects on vigor, bloom, and ripening dates, yield, and kernel weight. The effect of root stock on tree architecture is less clear. Rootstock effects on shoot length and shoot diameter have been reported,container growing raspberries but the magnitude of the effect varied as a function of specific scion-root stock combinations.

Similarly, the scion can influence root structure, primarily by altering auxin and cytokinin responses. This suggests the regulatory feedback between the root stock and scion ultimately modulates final tree architecture. The underlying molecular mechanisms of these interactions remains unknown. Studies of the effect of root stock on pecan scion vigor have demonstrated that common pecan root stocks vary by geographic region and have a diverse effect on scion growth. Before introducing clonal root stocks, open-pollinated seed stocks widely used for the vegetative propagation of commercial pecan cultivars had different growth responses. Grauke and Pratt evaluated bud growth of three pecan cultivars on seven open-pollinated seed stocks including ‘Curtis’, ‘Burkett’, ‘Elliott’, ‘Moore’, ‘Riverside’, ‘Apache’, and ‘Sioux’. They reported that scion growth was significantly influenced by root stock, with bud growth of ‘Candy’ on ‘Elliot’, and ‘Curtis’ root stocks were more than ‘Sioux’, ‘Riverside’, ‘Apache’, and ‘Burkett’ root stocks. Liu et al. studied the grafting-responsive MicroRNAs which are involved in growth regulation of grafted pecan and identified some miRNAs that regulate grafted pecan by regulating inorganic phosphate acquisition, auxin transport, and cell activity. The root stock effect on vigor of other nut trees has been less studied. In hazelnut, new root stocks have produced superior vigor compared to own-rooted varieties. This is an important improvement when trees are trained to a trunk, and not grown as bushes with many stems. Graft success depends on the root stock-scion physiological compatibility and the proper alignment of tissues in the graft union. Graft incompatibility is a complex physiological process defined by the adjustment of the metabolisms of the cultivar– root stock combinations, growth conditions, the presence or absence of viruses, environmental conditions, the nutritional status of trees, and as other stresses. Graft incompatibility can be detected by a variety of symptoms including poor graft success, yellow-colored leaves, slow vegetative growth, drying of the scion, a generally diseased appearance, symptoms of water stress, overgrowth in the graft area, thicker bark tissues of scion, and excessive sprouting on the root stock .

In pistachio, P. terebinthus, P. atlantica, P. integerrima, P. vera and their interspecific hybrids are commonly used root stocks. P. terebinthus is more difficult to bud than P. atlantica or P. integerrima due to scion-root stock incompatibility problems. Although root stock-scion incompatibility is not a serious problem in pistachio production, some evidence of incompatibility between P. veraas a scion and UCB1 as a root stock was observed in the late 1980s in the USA. This incompatibility appeared to be related to a single paternal P. integerrima tree used to produce the first UCB1 seedlings at the University of California, Berkeley. There have been fewer reports of root stock scion incompatibility since removal of this paternal tree. When facing root stock-scion incompatibility problems in pistachio it is worth testing different individuals within a single species to find a compatible genotype. The success of walnut grafting mainly depends on several factors such as root stock, scion, grafting methods, and environmental conditions. The specific graft incompatibility between different Juglans species has not been reported. Nevertheless, some literatures refer to black line disease as a delayed graft incompatibility in walnuts. California black walnut and its hybrids are considered as interesting root stocks for Persian walnut specially in California due to high vigor, resistance to soil-borne pests, and tolerance to saline and saturated soil. However, if Persian walnut was grafted on California black walnut and its hybrids and the tree was infected with CLRV virus, the symptoms of black line disease would appear, which is similar to a graft incompatibility. Therefore, in regions where there is a possibility of infection with the CLRV virus, Persian walnut is a more suitable root stock that can be used to avoid black line disease. Andrews and Marquez reported that black line disease has a long-delayed incompatibility where a CLRV virus migrates to a graft union. In almond, graft incompatibility appears to be genetically dependent. For example, ‘Nonpareil’ shows distinct graft-incompatibility on plum root stocks while the closely related ‘Carmel’ cultivar does not. Graft-incompatibilities can produce both slow general tree deterioration over time and distinct localized deterioration such as the stem-pitting decline seen on almond-Myrobalan plum combinations.

These more localized types of graft-incompatibility can often be observed as a weakness and occasional breakage at the graft-scion union. Because this often occurs at a critical time, when the tree is coming into bearing, several studies have pursued earlier physiological and molecular predictors of graft-compatibility as an aid to both breeding and orchard management. These studies generally involve anatomical, physiological, or molecular aspects of compatible graft union formation such as the similarities/differences in scion vs. root stock vascular size and configuration. Related studies have identified several molecular candidates that may contribute to compatible graft formation, however,raspberries in containers the specific cause and effect relationships remain vague. Studies have identified several metabolic pathways, including the phenylpropanoid pathway, cell wall biosynthesis, oxidative stress, and auxin signaling, that appear to be associated with graft-incompatibility, supporting the complex genetic control commonly encountered when breeding for this trait. Japanese and Chinese chestnuts are used in chestnut root stock breeding programs due to their root-rot resistance. The potential use of hybrid chestnut cultivars also has been evaluated; while incompatibility has been observed in the hybrids. Tokar and Kovalovsky grafted Chinese, European, and Chinese × Japanese hybrid chestnut cultivars onto European chestnut root stocks. The least successful grafting combinations were the Chinese × Japanese hybrid on European root stocks. Viéitez and Viéitez, used Chinese and European chestnuts for European, Chinese, and European × Chinese chestnut hybrid scions. The least successful grafting combinations were the Chinese root stocks with European chestnut cultivars.Soylu suggested that scions and root stocks of the same species should have better graft compatibility, but genetic intraspecies graft incompatibility was reported in Chinese and European chestnuts. Although graft compatibility in chestnut may be mostly controlled by genetic factors, graft success can also be affected by environmental factors, stress, and their interactions with genotype. Oraguzie et al. suggested that growing the root stock and the scion plant under the same environmental conditions would produce better graft compatibility. Oraguzie et al. divided graft incompatibility into two groups, early and late. Early graft incompatibility can be seen in the first two years and late incompatibility in 5 to 7 years. Chestnut mosaic virus can also induce graft incompatibility. The first hypothesis was suggested by Santamour et al.. They identified four different cambial peroxidase isozymes patterns in ten chestnut genotypes. They found that C. dentata, C. alnifolia, C. ashei, C. ozarkensis, and C. pumila species have A cambial peroxidase isozymes, C. crenata and C. seguinii have B pattern, C. sativa has A, B, and AB isozymes, C. henryii has A and B and C. mollissima has A, AB, B, and BC isozymes. Grafting plants with different isoenzyme bands could lead to graft incompatibility. Santamour tested his hypothesis with 200 Chinese chestnut seedlings. If the scion and the root stock belonged to the same cambial peroxidase isozymes group, the cambium layer in the graft area united and cambial continuity occurred. If the scion and the root stock cambial peroxidase isozymes groups were different, cambial continuity was interrupted. Thus, he suggested that cambial peroxidase isozymes groups could be used to predict graft incompatibility in Chinese chestnut. However, this hypothesis was not confirmed in subsequent study. The other hypothesis of graft incompatibility in Chinese chestnut is a mismatch of phloem fiber bundles. A very important aspect of this anatomical structure is the presence of a fiber bundle in four or more places in the branch. When the seedlings are 2–3 years old, phloem fiber bundles can be better distinguished. This situation should be considered when grafting, as the cambium of the root stock and scion may not combine uniformly. Given the importance of early detection of graft incompatibility, it is important to find specific markers for prediction in different root stock-scion combinations. Many studies have addressed strategies for compatibility detection such as phenolic marker identification and peroxidase isozyme studies.

Phenolic compounds, whose biosynthesis is triggered by wounding and infections, are produced and accumulated during the callusing phase. This suggests that quantitative and qualitative differences in phenolic patterns between scion and root stock may predict graft union dysfunctions and could be potential markers of graft incompatibility. Research at the University of Torino Chestnut R&D Center, demonstrated different chemical markers: six phenolic acids, five flavonols, two catechins, and two tannins. Chromatographic methods were used to identify and quantify the main bioactive compounds, benzoic acids, binnamic acids, batechins, flavonols, and tannins and obtained specific phytochemical profiles. Benzoic acids , catechins , and tannins were used to establish specific profiles for distinguishing compatible and incompatible chestnut scion-root stock combinations. Another promising technique is the analysis of peroxidase isozyme profiles of root stocks and scions. It appears peroxidases play an important role in grafting, as these enzymes are involved in lignin formation and lignin–carbohydrate bonding. Differences in peroxidase isozymes in root stock and scion graft performance have been reported in Chinese chestnut and peach–plum combinations. Other strategies for evaluating root stock–scion compatibility include describing the phenylalanine ammonia-lyase transcriptomic-level and phenotypic evaluation.Another important trait in root stock selection is suckering. Suckers not only divert water and nutrients from the main trunk, but also increase orchard management costs incurred in removing them. Suckering is an important issue in hazelnut cultivation, requiring four to five herbicide sprays per year in commercial orchards and occasional hand-removal in winter. This situation could be improved by use of non-suckering root stocks. Currently, three types of hazelnut root stocks are in use: C. colurna seedlings, C. avellana seedlings, and two clonal selections from open pollinated C. colurna: ‘Dundee’ and ‘Newberg’. A hazelnut root stock trial in IRTA-Mas Bové, Spain in 1989 led to selection of a clonal C. avellana root stock , which is a seedling of ‘Tonda Bianca’. One of the first European hazelnut root stock trials was conducted in Nebrosi, Sicilia in 1970 to compare self-rooted trees grafted on C. avellana root stock . After 12 years of evaluation, self-rooted trees showed better vegetative and productive behavior than grafted ones. Experience with C. colurna in the U.S.A. has demonstrated that members of this species are more drought tolerant and cold hardy than C. avellana cultivars. The C. colurna was non-suckering, deeply-rooted, and graft-compatible with all C. avellana cultivars and Corylus species, suggesting its potential use as a root stock. Due to differences in bark color and texture, the union between the Turkish and European hazelnut is readily evident. However, the Turkish hazelnut is difficult to propagate and its seedlings often require two additional years before reaching sufficient size for grafting.