中文摘要：

以云南稻核心种质和云南主栽籼稻品种滇屯502、粳稻品种合系35配制的杂种BC3F5和BC4F4（172份）为材料，在云南新平相同栽培条件下种植，研究供体亲本及其回交后代稻谷粒形性状的遗传变异．结果表明：1）供体亲本及其后代的谷粒长和谷粒宽遗传力较高，且均表现出较高的遗传变异，选择潜力较大．2）谷粒长、谷粒宽和谷粒长宽比3个谷粒性状的遗传变异度不同．利用供体亲本及其后代进行粒形新品种选育时，除应考虑各谷粒性状的表现特点和遗传潜力大小外，还应考虑籼粳、稻谷粒形、供体亲本与其后代的遗传差异和特点．3）籼粳间、稻谷粒形间的3个谷粒性状多样性指数均较高，表现出显著的粒形多样性．遗传改良可使粒形多样性明显降低，表现为籼稻大于粳稻，阔卵形大于椭圆形和中长形．

英文摘要：

The BC3F5 and BC4F4 （172）, backcross hybirded by Yunnan rice core idioplasm and Yunnan rice landrice Diantun 502 （Oryza satica）, hexi 35 （Oryza satica） were taken as materials, and their genetic variation of grain shape characteristics were studied planted under similar environment in Xinping county of Yunnan province. The results showed： 1） Grian length（GL） and grain width（GW） from donor parent and backcross hybrids produced great habitability and genetic variation. The potential selection of these traits were high. 2） The degrees of genetic variation of three shape characteristics office grains, GL, GW and GL/GW were different. The expressional characteristics and value of genetic potential of each grain character should be considered while selecting new variety by donor parent and backcross hybrids. In addition, the genetic differences and characteristics ofindica and japonica, different shapes office grain, donor and backcross hybrids should be considered. 3） The average diversity index of three shapes characteristics of rice grain was high between indica and japonica; There was a significant diversity in grain shapes. Genetic improvement led to a decrease in diversity of grain shaps, greater decrease in indica than in japonica, greater decrease in ovum shape than in oval shape, but a moderate decrease in rectangularity.