Evaluation of Cold Tolerance at Booting Stage and Cluster Analysis for Japonica Rice Landraces in China

The cold tolerance at the booting stage of 329 japonica rice landraces from 18 provinces in China were evaluated under natural low temperature and cold water irrigation,and the cluster of different landraces was analyzed.The result showed that performance of cold tolerance at the booting stage and main agronomic traits associated with cold tolerance among the landraces had significant differences under natural low temperature and cold water irrigation.Seed setting rate and cold water response index(CRI) of the landraces from Tianjin,Sichuan and Taiwan,which had stronger cold tolerance,and not sensitive to cold water at the booting stage,were higher than those of other provinces under natural low temperature and cold water irrigation.Yunnan japonica rice landraces showed stronger cold tolerance(seed setting rate) at booting stage under natural low temperature,and CRI of sowing to heading days and plant height were also higher,and not sensitive to cold water under cold water stress.From the overall trend,beside specific provinces,the cold tolerance(seed setting rate) at booting stage of landraces from relatively higher latitude of north provinces were stronger than those from relatively low latitude of southern provinces.In addition,the cluster results of the landraces were closely associated with geographical location and cold tolerance under natural low temperature and cold water irrigation.Moreover,the cluster results were more closely correlated with geographical location under cold water stress than that of natural low temperature.