两系法杂交水稻研究的进展

 两用核雄性不育系是两系法杂交水稻的基础，我国现已育成17个达到规定标准的两用核不育系。根据育性对光温条件的不同反应，它们分为光敏型和温敏型两个基本类型，在生产上均有实用价值，但要因地制宜选用。两系法品种杂交水稻已经研究成功，一批优良组合开始在生产上试种和示范。两系法亚种间杂交水稻的选育也取得了很大的进展。

PROGRESS OF TW0-LINE SYSTEM HYBRID RICE BREEDING

Recently two new kinds of rice genetic tools viz., photoperiod sensitive genic male sterile (PGMS) lines and thermo-sensitive genic male sterile (TGMS) lines have been successfully developed in China. Their male sterility is mainly controlled by a pair of recessive nuclear genes, and has no relation to cytoplasm. Exploitation of these MSlines to develop hybrid rice has the following advantages over the classical three-line or CMS system:1. B line is not needed. Under longer daylength the PGMS lines or under higher temperature the TGMS lines show complete pollen sterility, thus they can be used for hybrid seed production in these conditions. Under shorter daylenghth or temperate conditions they show almost normal fertility, thus can multiply themselves.2. The choice of parents in developing heteroic hybrids is greatly broadened.Studies showed that over 97.6% varities tested (within subspecies) can restore such MS lines. In addition, PGMS and TGMS genescan be easily transferred to any rice cultivar.3. There is no negative effects caused by sterile cytoplasm and the unitary cytoplasm situation will be avoided.Several better inter-varietal hybrid combinations produced by two-line,system were under regional trial and farmer's field trail in 1989.The results were promising, some of them outyielded the best existing hybrids by about 5%. It is estimated that the planting area of two-line system hybrid rice will be extended more than 17,000 ha in 1990.The development of inter-subspecies especially indica/japonica hybrids with very high yield potential through two-line system is still under way.The major problems presented in such F_1 hybrids, namely semi-sterility, too tall plant height and long growth duration, have been overcome. But the plumpness of many fertilized grains is not good in most combinations. Now, efforts are focused on solving this problem.