Fresh tomatoes must have acceptable flavor, color, texture, and other taste parameters to satisfy consumer demands and handling requirements. Processing tomatoes, on the other hand, must have intrinsic rheological characteristics that make them suitable for various processing applications, such as juice, ketchup, or sauce production. Traditional breeding requires the selection of a tomato genotype or a related wild species that has a desirable trait, such as early ripening or disease resistance, and crossing it with another tomato cultivar that has a good genetic background. The desired result is an earlier ripening tomato that makes it to the market sooner, or cultivars that resist pathogen attack. In this way,nft channel several thousands of tomato cultivars have been developed over the years. The final goal of vegetable breeding programs is then to release new cultivars having elite combinations of many desirable horticultural characteristics.
Consumers are seeking new eating experiences, different quality attributes and improved convenience, and are prepared to pay a premium for such produce if their expectations are met. Plant breeding for improved taste, convenience, and consumer appeal has already contributed to increased per capita vegetable consumption with the development of products such as baby carrots, yellow and orange peppers, cherry and pear tomatoes, non-bitter cucumbers, mild tasting eggplants, seedless watermelons, and lettuces with different colors, textures and flavors for baby leaf and precut salads. In some instances, these premiums are considerable and bring benefit to the overall vegetable industry through improving the popularity of the vegetable crop overall. Further, the premiums achieved can exceed those that consumers are prepared to pay for the choice of consuming organic produce. Other important objectives of vegetable breeding are disease and pest resistances. Since the early days of the 20th century, traditional breeding for disease resistance in vegetables has been a major method for controlling plant diseases.
Cultivars that are resistant or tolerant to one or a few specific pathogens are already available for many vegetable crops. Resistant hybrids with multiple resistances to several pathogens exist and are currently used in vegetable production. For example, in tomato, the genetic control of pathogens is a very useful practice and most resistances are monogenic and dominant. So far, tomato breeding has resulted in cultivars with resistance to at least 15 pathogens, hydroponic nft although with varying stability and level of expression . Tomato cultivars with some resistance to fungi or oomycetes , bacteria , virus , and nematodes are available.With the increasing use of F1 hybrids it is possible to use cultivars combining from four up to six resistances . Pest resistance is essential in vegetable production but is marginal in vegetable breeding research. There are few vegetable cultivars resistant to insects. Resistance may be unstable due to genetic variants of the insect that are able to overcome that source of resistance. Depending on the complexity of the interaction between the pest and the vegetable plant, plant resistance may break down rapidly or be long-lived. Insects, including aphids, whiteflies, thrips and leafhoppers, are also very important in vegetables because they vector many viruses.
Viruses can substantially reduce production and quality and are be-coming increasingly problematic worldwide due to the absence of virus resistant germplasm for many important vegetable crops. Aphid vectored viruses are particularly problematic because many are transmitted in a non-circulative and non-persistent manner . This means that a very short time, i.e. a few seconds or minutes, is sufficient for aphids to acquire virus particles when probing on infected plants. A similarly short time period is enough for aphids to release virus particles when probing on healthy plants. The primary injury caused by aphid-vectored viruses arises not from direct feeding damage by the aphids, but from their ability to allow the virus to enter the plant and initiate the disease. A successful application of biotechnology has been the development of vegetable cultivars that resist insect transmit-ted viruses, as well as cultivars that directly resist insect feeding or development. Bt potato cultivars expressing resistance to Colorado potato beetle , and aphids associated with potato virus Y, and potato leaf roll virus, were approved for sale in the United States in 1995. The economic return of investment in breeding for disease and pest resistance may be low because it is dispersed among many different vegetable crop types. Also resistant cultivars compete directly with non–resistant ones that may still be used by growers with minimum problems.