Analysis on cold tolerance at seedling stage of the backcross hybrids of Indica with core collection for rice landrace in Yunnan

The low temperature of early spring and the continual rain is the primary factors causing Indica(Oryza sativa L. ) rotting seedlings, screening endures cold the idioplasm resources, induct the cold resistance gene the high production in the Indica(Oryza sativa L. )variety are prevented the low temperature cold damage is most economical the effective method. It cold provide conditions for Indica(Oryza sativa L. ) cold resistance breeding to enhance its hybrid descendant’s seedling stage cold resistance research. Under natural low temperature in Kunming, Cold tolerance at seedling stage of parents and hybrids at 3 leaf stage were analyzed by using parents Indica core collection rice landrace in Yunnan for 235 accessions and yunnan domain varierity Diantun502 for Indica(Oryza sativa L. ), and their F5, BC1F4, BC2F3 and BC3F2 generations. The result shows that: (1) There is big differences of seedling stage endureing cold during different backcross generation and the hybrid and the parent. The whole trends is the backcross donor parents F5BC1F4BC2F3BC3F2 . The cold tolerance of seedling stage for backcross hybrids decreased while the increase of backcross generation, and it was tend to the cold tolerance of backcross parent. It is easy to to obtain the material to endure cold in the seedling stage by chosing the backcross donor parent and the early generation material during the breeding of enduring cold. (2) The backcross donor parent seedling stage endures cold much more strongly than the hybrid descent in the same rice cropping region. The variated trend of cold tolerance at seedling stage is close between Donor parents and hybrids F5 between rice cropping region, In central yunnan single cropping region of indica-japonica and northeast Yunnan plateau japonica region material endures cold strongly. there was great difference in BC1F4、BC2F3 and BC3F2 between rice regions and generations.