Genetic Variation of Cold Tolerance Characters of Yunnan Rice Landraces at Indica and Japonica Rice Cropping Regions

Genetic variation of chaff and anther size and seed setting rate at indica rice cultivated region, and warm cool region of japonica rice, and mixed belt of indica and japonica rice cultivated using 15 crosses and five different cold tolerance parents.The results are as follows:(1) Narrow chaff, stable anther size and higher seed setting rate were observed in cold damage condition.There was a negative correlation between anther shorting rate and seed setting rate;and the weakest cold tolerance Towada was the most significant (0.924 ** ).(2)GCA is higher for Kunmingxiaobaigu and Lijing 2 with the strongest cold tolerance. Some near isogenic lines with cold tolerance have been bred using Kunmingxiaobaiogu and Lijing 2 for the donor of cold tolerance gene, and Towada for recurrent parents. (3) SCA and cold tolerance characters differ from generation and rice cropping regions.(4) Variation of indica character and cold tolerance gene accumulated at warm cool region of japonica rice, and genetic evolution to indica characters.