TNAG-2110-FCO40-3009-Hong-Kong-participation-in-international-organisations-1990 — Page 229

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Faster Breeding, Better Targeted

7.

Conventional breeding approaches in one place require about 15 years or so to develop and release a new crop variety. Biotechnology can shorten the process. Using anther and microspore culture for production of haploids and homozygous lines, Chinese, Indian and Korean scientists have developed new varieties of rice in shorter durations. It took Chinese scientists only four years to develop the important variety SH528 in Shanghai. Using this method, Indian scientists have developed two promising rice varieties, R4 and R10.

8.

grapes, and

Chinese scientists have succeeded in inducing haploids in about 40 different plant species. They were the first to produce haploids through in vitro culture in wheat, maize, sugarcane, soybean, rubber, apple. Already 60 varieties/lines of rice and 20 varieties of wheat have been released through the use of haploids. The Republic of Korea released two rice varieties derived from anther-culture-haploid technique and screens annually about 6000 anther-derived rice lines. The technique has also been effective in heterosis breeding of Chinese cabbage. China and India are using this technique for exploitation of germplasm and breeding of potato and sweet potato.

9.

Positive selection of individual plants in segregating populations for many desirable attributes is not possible. This problem can be obviated if such genes are tagged with some marker genes. Biochemical markers, such as the linkage of the enzyme endopeptidase with the gene for eyesopt resistance in wheat, are now becoming available for identifying the desired carriers. DNA markers, in form of restriction fragment length polymorphisms (RFLPs), will enable the breeder to select without the need to score for the character of economic importance. Work is advanced with several important crops viz. rice, potato, tomato, wheat, barley, maize, etc. in China, India and Korea. These developments confer a degree of precision in selecting desired gene combinations.

Improved Productivity and Quality

10. HYV technologies were not available for pulses, oilseeds, and several roots and tubers. While the conventional breeding approaches have not been as successful in these crops as with cereals, biotechnological approaches, particularly tissue culture, somatic hybridization and even transformation are standardized for several of these crops and should be utilized for incorporating genes for increased photosynthetic efficiency, resistance against pests and diseases, tolerance to stress conditions and for quality traits viz. protein content, amino acid balance, oil content, fatty acid profile and composition, as well as freedom from antinutritional factors. It has already been shown that wheat protein genes can be engineered into the tobacco seed. Thus, it should be possible to engineer high sulfur-amino acid containing proteins of wheat into legumes and conversely high lysine content of pulses into wheat and other cereals. A potato line has been engineered which has a protein content of more than 4 percent against the usually less than 2 percent. In Pakistan, soybean protein gene is being cloned to improve the methionine and cystein contents of chickpea seed protein.