It is noteworthy that at harvest only two transcription factors were differentially expressed, both showing higher expressions in T fruits and in the case of the ortholog of PAP2/IAA27, also at 1 week of cold storage . SlIAA27 silencing results in greater auxin sensitivity in tomato. Moreover, a gain-of-function mutation in IAA16 confers poorer responses to auxins and ABA in Arabidopsis. Thus, it is likely that high levels of these genes at harvest contribute to delay the ripening program or protect fruits LS during cold storage, at least at the beginning of cold storage. The analysis of the expression profiles during cold of the genes differentially expressed in M fruits resulted in important and unexpected expression characteristics. In fruits LS, these genes behaved like ripening genes and were able to continue with the ripening program in the cold in fruits LS, while the ripening expression of other ripening genes was normally halted , which is not the case of high sensitive fruits. The ability of cold to stop fruit ripening has been previously reported, even if no details of how this happens at the molecular level have yet been provided. Although we have no hypothesis about why these genes continued with the ripening program in the cold , we believe that this may be because these genes are part of the adaptation mechanism or simply reflected that LS fruits perform better in the cold than S fruits. In apples the ability to set up ripening during cold seems to be an adaptative mechanism to shorten ripening time in colder autumns. On the other hand, 25 liter square pot this unexpected behavior of some of the genes differentially expressed at harvest indicates that they not only can form part of a mechanism for the interaction between endogenous and exogenous signals, they could also be able to contribute to mealiness in response to cold stress.
In light of this, it is interesting to remember that environmental/ripening stage/cultural preharvest practices have a strong effect on CI sensitivity during the post harvest which, together with the genetic background, may be responsible for the differences noted in the M stage that condition the cold response.Fruit trees differ from landscape trees in that they are best kept relatively small to facilitate routine pruning, fruit thinning, managing pests, and harvesting fruit from the ground or a ladder. Fruit trees that are allowed to grow above a manageable height produce excessive fruit, leading to branch breakage, smaller-size fruit, and, in some cases, pest problems . Most fruit trees are trained to the open center system and are topped annually to reduce limb breakage. However,some fruit trees lend themselves to central leader training, so these considerations are less important. The major problem with those that do grow very tall, however, is that the fruit are borne higher in the tree and the lower branches become shaded. This results in the decline of these branches and ultimately renders them fruitless. Unlike fruits, nuts are knocked, shaken, or allowed to fall. They are not usually picked by hand, so tree height is less important. Some size control is necessary for preventing branch failures and maximizing nut production, because large trees are more difficult to knock. Pruning of nut trees generally consists of thinning or cutting back selected branches to suitable lateral branches. Walnut and pistachio trees should be trained to a modified central leader to maximize fruit production and maintain a branch structure that can support the nut crop .The best strategy for keeping trees relatively small is to use a dwarfing rootstock when available. However, semidwarf rootstocks differ in their ability to cause dwarfing, and many semidwarf trees sold in retail nurseries are only slightly dwarfing. For example, apple rootstocks can range from about 80 percent of the size of a standard tree to about 60 percent to about 30 percent . Therefore, some semidwarfs are still, practically speaking, full-size trees. Other fruit species do not have this range of dwarfing rootstocks available, and most are only slightly dwarfing. For the stone fruits, such as peaches and nectarines, the dwarfing rootstock most commonly available is Citation, which produces a tree that is somewhat smaller.
Citrus can be dwarfed to approximately 50 percent by growing trees on the ‘Flying Dragon’ trifoliate orange rootstock. However, availability of trees grafted to ‘Flying Dragon’ is limited due to the very slow growth of grafted trees. Genetic dwarf trees are very easy to manage and are aesthetically pleasing in the landscape . They naturally produce short internodes and are usually planted on standard rootstocks. A limited number of genetic dwarf varieties are available for almond, apple, apricot, nectarine, and peach.Deciduous fruit and nut trees are ideally planted bare root, but containerized trees can also be used. All bare-root trees intended solely for fruit or almond production should be headed 18 to 24 inches above the ground at planting to force low branching; walnuts and pecans should be headed higher. If this were not done, the first laterals would typically form around 5 to 6 feet above the ground, growth would be weak, and much of the fruit would be out of reach from the ground. It is important to develop a new leader in headed trees if the central leader method is to be maintained. Select one of the shoots that grow near the heading cut, and tie it to a stake in an upright position if it is not growing upright naturally. Additional pruning may be needed to eliminate branch crowding or prevent codominant trunks from forming. Higher branching may be desirable for fruit trees in some urban settings to allow for maintenance of vegetation under and around the tree. In areas where deer are a problem, lower branching may not be practical without proper protection. Containerized fruit trees are often planted in spring or summer, so they cannot be headed without removing all the foliage. Either leave the tree as it was headed in the nursery, or make the lower heading cut in the next dormant season. In hot regions where afternoon sun hits the trunk, apply a white interior latex paint diluted 50-50 with water to the trunk to prevent sunburn injury.Each fruit and nut species has a preferred training method based on the species’ growth habits and fruiting characteristics. Ideally, most of the fruit should be produced low in the tree to facilitate fruit thinning, pest management, and harvest. Because fruit is produced on spurs or 1-year-old branches that require sunlight for flower development, direct sun must penetrate into the lower portions of the canopy for fruit production low in the tree. Nearly all fruits and nuts are borne mainly on spurs, but peach and nectarine fruit are borne only on 1-year-old shoots that grew the previous summer. Most stone fruits and almonds are best trained to the “open center” or “open vase” method, where the center of the tree is routinely kept free of vigorous shoots. In this manner, lower fruiting branches receive sufficient light through the tree’s center. Apples and pears can also be trained to the open center system but are better adapted to central leader training, where lateral branches are trained outward from a vertical leader allowing sunlight to penetrate from the sides.
Persimmons are also well adapted to central leader training. For apples and pears it may be prudent to develop two or three leaders in case fire blight kills one of the leaders; lateral branches are directed to the outside of the tree. Apples and pears can also be espalier trained. This method involves pruning the tree to form a narrow, gallon pot flat plane on a trellis or against a wall or fence. Permanent, horizontal branches that resemble cordons on grapevines are selected to produce the fruiting spurs. Walnuts, pistachios, and persimmons can also be initially trained with a central leader, but then trees are allowed to develop a natural rounded crown; this method is referred to as “modified central leader” training. Fig trees can also be trained using this method or using open center training, and they can be kept fairly short or allowed to grow tall, or they can even be espalier trained. Modified central leader training can be used for pomegranates, but their rangy growth and constant root suckering make them better adapted to a system that allows them to grow into a large multit-runked bush. Pruning them typically involves heading back and thinning vigorous upright branches and removing old trunks or scaffold branches to rejuvenate trees. Citrus trees can be allowed to grow with little training except to eliminate scaffold branches with narrow crotch angles. Manage water sprouts by heading, shortening to a lower lateral, or, in some cases, completely removing. Save water sprouts that bend over, ultimately contributing to the typical mounding citrus canopy. Remove all root stock suckers; they often grow up the center and are difficult to see. Painting the trunk white not only helps to prevent sunburn but will also make root stock suckers easier to spot. Over time, the shaded inner fruiting branches of citrus trees die, and fruit production moves to the top and sides. This characteristic is considered acceptable for citrus. Citrus trees can also be hedged, and they are very adaptable to espalier training. Nearly all species can be trained as fruit bushes, using a method in which trees are trained in the first and second year by heading shoots when they reach about 2 feet in length. The resulting new shoots are headed again, and this is followed each time by some thinning of shoots as well. Once the desired tree height is achieved , pruning consists of removing shoots above the desired height and thinning remaining shoots and branches about twice a year. Nearly all pruning on fruit bushes should be done in the growing season to reduce their vigor, but touch-up pruning is useful in winter, when branch structure is more visible. Apricots and cherries should be pruned only in late summer, when dry weather is predicted for an extended period. These species are susceptible to branch canker diseases, caused mainly by Eutypa and Botryosphaeria fungi, which infect branch injuries made before or during wet weather or periods of very high humidity. However, most other fruit and nut trees can be pruned any time enough leaves have fallen to make the tree structure visible.After planting and heading bare-root stone fruit trees, two options are possible for the resulting shoots. Either they are allowed to grow through the summer, or training can begin during the first growing season by selecting three or four well-placed shoots when they are 1 to 3 feet long and heading back all other shoots to 4 to 6 inches. By winter, the primary scaffold branches are selected and headed, and all other upright branches are removed. Continue to develop the tree to a vase shape over the next 2 years. Ideally, each primary scaffold should branch into two secondary branches, which, in turn, branch into two tertiary branches. Prune out vigorous upright shoots in the tree’s center in winter, and maintain the open center by removing vigorous upright shoots once during summer. In winter, thin fruiting branches to reduce fruit load and minimize the need for fruit thinning. Head the trees back to about the same height every year, preferably to a height that can be reached using only a short ladder . With almond trees, scaffold branches are selected as with stone fruit trees. After that, however, the opening in the center of the tree can be somewhat narrower than stone fruit trees. Annual pruning involves thinning branches to avoid overcrowding.Apples, pears, persimmons, and pecan trees are best trained to develop a central leader similar to those in many shade and ornamental trees . Lateral branches grow outward from the leader, either in tiers of approximately four branches each or spaced fairly uniformly up and around the trunk. Rather than simply allowing the trunk to continue growing naturally after planting, the trunk is headed at about 18 to 24 inches above the ground, and the most vigorous and upright shoot that develops is selected to become the new leader. This practice is done to force the first tier of four lateral branches below the heading cut. When the new leader has grown about 2.5 feet, it is then headed back about 6 inches.