i
production of ginseng saponins from Panax ginseng. Diasgenin, a female contraceptive produced from in vitro cultured Dioscorea spp. and a male contraceptive based on gossypol from tissue-cultured Gossypium spp. are under extensive trials in China. In addition, tissue culture technique has been successfully used in the cultivation of Scopolia acutangular, Artemisia annua, and Rauwolfia yunnanesis. India is also using this technique for production of diasgenin and other medicinal and aromatic products.
17.
The exploitation of in vitro culture technique, although ideally suited to developing countries, is not being effectively used in several countries. This gap is due to poor development support and inadequate linkages among development agencies, private sector and farmers. However, there are certain exceptions. For instance, Thailand provides a successful example of integration of public, private and grower sectors for in vitro selection, micropropagation, and distribution of orchid planting materials, field growing of selected clones by contract growers, and marketing and export of flowers. Such experiences should be documented critically and shared with other countries in the Region.
Increased Resistance to Biotic and Abiotic Stresses
18.
Biotechnology holds great promise for alleviating the losses, estimated at about 30 percent, due to pests and diseases. Besides freeing the desired clones of viruses, viroids and other pathogens and increasing the ability to diagnose pathogens, two developments, namely, de novo synthesis of biopesticides by the host plant for its own defence, and microbial sprays, have opened tremendous opportunities for pest management.
19.
Genes for de novo synthesis of toxins against certain pests have been engineered into plants and are being field tested. However, so far none of the engineered plants are being commercially exploited. Nevertheless, tobacco, tomato, soybean and cotton have been made resistant, by the introduction of bacterial and fungal genes, to the herbicides glyphosate and chlorsulphuron. Genes from Bacillus thuringiensis or cowpea engineered into potato and tomato have rendered these species resistant to insects. Similar work is in progress on maize. Resistance to virus diseases has been engineered into potato, tomato and cotton. Resistance to brown plant hoppers in rice is being biotechnologically transferred from wild related species.
20. Besides developed countries in the Region, China has already produced transgenic plants of tobacco resistant to cucumber mosaic virus (CMV). Soybean lines resistant to herbicides have also been produced. An insect-killing-gene has been introduced in rice. These lines of tobacco, soybean and rice derived through genetic transformation are under observational trials before being recommended for general use.
21. India is exploiting the technology of spraying Bacillus thuringiensis suspensions for biological control of insect pests. Pakistan is also using this technology for controlling lepidopterous pests in oilseeds. In the Republic of Korea, work is in progress on (i) standardization of a model system for plant gene transformation; (ii) isolation and identification of useful genes by isozyme technique and other techniques, particularly for antibiosis against white-back plant-hopper, an antagonist for soil-borne diseases and resistance to rice virus; and (iii) improvement of vector for plant transformation. In Thailand, genetically engineered coat protein cross protection against two major virus diseases of papaya and tomato has been established. It is expected that transgenic papaya and tomato plants