Exploitation of latent cool-injury resistance genes among rice cultivars grown in warm region.

拟开发水稻孕穗期耐冷新基因（以下称简单性耐冷基因）。为了鉴定新的耐寒基因，进行了耐寒基因分析和耐寒试验系的开发。对易感系EG3和耐受性系EG5杂交的F3和F4系进行分离分析，发现EG5携带两个互补的耐受性显性基因。EG3/Aikoku3（耐受性品种）和EG3/CTH5（早草源引种耐受性品种）杂交结果表明，耐受性亲本均携带至少两个耐受性基因。比较EG3/Rikuu20和EG3/Shinriki杂交组合获得的F3株系，前者大部分具有耐受性，后者大部分具有易感性。结果表明，Aikoku来源的耐受性基因为显性基因，Shinriki来源的耐受性基因为隐性基因。同时，利用CTH5和Kirara397近等基因系对高耐受性品种锡勒瓦耐受性基因的功能进行了研究。抽穗前1个月将植株置于冷水浴中（冷处理），观察冷水对花药长度、花粉肥力和种子肥力的影响。与耐受性基因型无关，所有品系的花药长度都有所减少。冷处理植株的花药变白变薄，而对照植株的花药变黄变厚。在相对花药长度方面，有耐受性基因的品系比没有耐受性基因的品系减少得更少。在花粉育性方面，前系育性高于后系。由此可见，耐受性基因的作用不仅表现在花粉的育性上，还表现在雄性生殖器官的生长上。

Exploitation of new genes for cold tolerance at booting stage of rice (Hereafter these genes are called tolerance genes for simplicity) was intended. To identify new tolerance genes, gene analyses for cold tolerance and development of new tester lines for cold tolerance were carried. Segregation analysis using F3 and F4 lines derived from the cross between EG3 (susceptible line) and EG5 (Aikoku : tolerant line) revealed that EG5 carried two complementary dominant genes for tolerance. Results from crosses of EG3/Aikoku3 (tolerant variety) and EG3/CTH5 (introduced tolerance from Hayakogane) suggested that both tolerant parents carried at least two tolerance genes. Comparing F3 lines derived from the cross combinations of EG3/Rikuu20 and EG3/Shinriki, most of the F3 plants were tolerant in the former combination while most of them were susceptible in the latter combination. This indicated that tolerance gene of Aikoku origin was dominant and that of Shinriki origin was recessive. Also, function of tolerance gene was investigated using CTH5 and near isogenic lines of Kirara397 for tolerence gene of Silewah (highly tolerant variety). Plants were put into the cold bath one month before the heading time (cold treatment) and effect of cold water on anther length, pollen fertility and seed fertility were observed. Irrespective of genotype for tolerance, all lines were severally reduced in anther length. Furthermore, anthers of plants grown under cold treatment become white and thin, while those of control plants were yellow and thick. For the relative anther length, lines with tolerance gene showed less reduction in it than the ones without tolerance gene. In pollen fertility, the former lines showed higher fertility than the later. Thus, it was suggested that effect of tolerance gene was expressed not only in pollen fertility but also in the growth of male reproductive organs.