Biotechnology in Horticultural Crops Biotechnology offers a vast potential in horticulture. Genetic transformation, micropropagation, in-vitro conservation of germplasm, synseed technology, virus-cleaning through STG techniques, biofertilizers, biopesticides and postharvest biotechnology are important areas in biotechnology of horticultural crops. Gene transfer has been attempted through Agrobacterium mediation and particle bombardment process to introduce DNA inside cells. In fruit crops, gene transfer is limited due to slow response of the techniques. Nevertheless, a number of important genes have been transferred in certain apple rootstocks for resistance to Erwinia amylovora, in cirtrus for resistance to tristeza virus, in apple for scab and fire-blight resistance and in papaya for ring-spot disease resistance. Owing to easy transformation in vegetables, 11 transgencis of tomato have been released since 1998. Insect resistant transgenic in tomato have been produced by incorporating Bt protein against fruit-borer and other Lepidopteran insects. In squash, a virus resistant transgenic "Freedon II’ against watermelon mosaic virus 2 (WMV2) and Zucchini yellow mosaic virus (ZYMV) has been released. In many ornamental and flower crops, transgenic plants have been made. Petunia has been a model plant for gene transfer studies. Introduction of DFR gene from maize has led to the development of transgenic petunias with brick-red flowers. In root and tuber crops, molecular maps of cassava and sweet potato are under construction. Transgenic cassava plants have been developed. Transgenics having resistance to common mosaic virus (CCMV) through viral coat protein mediated resistance and for African cassava mosaic virus (AC) with a dysfunctional ACMV genes are identified. In sweet potato, transgenic sweet potato resistant to pest Cylas formicarus has been claimed. At the Central Potato Research Institute (CPRI), Shimla, several transgenic potato lines have been developed expressing a synthetic analog of truncated cry 1 Ab gene. In USA, a transgenic potato cultivar. ‘New LeafTM’ has already been commercialized by the Monsanto company. Successful cryopreservation of seeds, meristems, somatic or zygotic embryos have been reported in cassava, potato, coconut, citrus, Prunus sp., Allium sp., taro, yam, black pepper, cardamom and grapes. Freezing of encapsulated meristems is possible in pears, strawberry and potato. In-vitro germplasm storage is now routinely followed in horticultural crops. Genetic manipulation through biotechnology to develop more efficient strains of nitrogen-fixing and phosphorous-solubilizing microorganisms is likely to increase biofertilizer efficacy. Biotechnology has enhanced the efficiency of output of processes producing biocontrol agents. Baculo viruses, nuclear polyhedrosis viruses (NPV), granulosis virus (GV), Trichoderma species and genus Bacillus are often used as biocontrol agents, Bacillus thuringiensis (Bt) based biopesticides are largely used in fruits, vegetables and potatoes. Commercial formulation of Bt is now available to control a number of insect pests in different horticultural crops. Application of genetic engineering in postharvest biotechnology is slowly taking shape and cloning of genes paved the way for creating plants with delayed ripening in fruits. The transgenics in tomato and apple with inhibited ACC synthese gene expression have been developed with delayed ripening and prolonged shelf life. The longer shelf life and better fruit quality can also be obtained by manipulating genes other than ACC synthase and ACC oxidase. Genetically Transformed Horticultural Crops
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