Evaluation Of Cold Tolerance At The Booting Stage And Analysis Of Genetic Diversity For Japonica Rice Landrace In China

The booting stage of rice is the most sensitive to low temperature at whole growth period, which causes the most serious yield loss. Therefore, correct identification and evaluation of rice germplasm resources to cold tolerance and selection of germplasm to cold tolerance for rice breeding have an important practical significance. Moreover, even though the rice yield has been increasingly growing in our country recent years, breeders focus on limit numbers of rice varities and exclude rice landrace and wild relatives of rice, which cause a great loss of genetic diversity and narrow genetic basis. So it is vulnerable to sudden natural disasters and pest invasion, and have a serious influence on rice production. Therefore, the study of genetic diversity in rice has important theoretical significance and practical value to our excellent genetic resources protection and utilization.The cold tolerance at the booting stage for 331 Japonica landrace varieties from 20 provinces of China were evaluated under natural low temperature and cold water irrigation, and the dendrogram among different provinces was analyzed. This study was conducted based on 72 pairs SSR markers for the assessment using 328 Japonica landrace varieties, and investigated the genetic diversity and cluster analysis of different provinces and different rice cropping regions. The results were as follows:1) From the whole trend, beside specific provinces, the cold tolerance of Japonica landrace varieties from relatively higher latitude of northern provinces were stronger than those from relatively low latitude of southern provinces. The cluster results of Japonica landrace varieties from different provinces were closely associated with geographical location and cold tolerance for Japonica landrace varieties under natural low temperature and cold water irrigation.2) Heikezhan, Hongmangdazu, Hongxuguizhouhe, Lengshuigu, Xunuo etc, 31 Japonica landrace varieties with higher cold tolerance at the booting stage were selected. Among them, Heikezhan from Guizhou province showed the highest cold tolerance at the booting stage under natural temperature and cold water stress.3) The cold tolerance at the booting stage under natural temperature was positively correlated with that under cold water stress (r=0.3378**). Results of two identification had a high consistency.4) Correlation analysis showed that it was necessary to choose that the height was relatively high, relatively early maturity and longer panicle materials at low temperatures to improve efficiency of rice germplasm selection for cold tolerance.5) Compared with Indica landrace varieties, genetic diversity of Japonica landrace varieties in China was more abundant and had more rare allelic variations.Japonica landrace varieties in the Central China and Southwestern region had abundant gene resources, whereas in Northeastern region, gene diversity was relatively low and it should explore new germplasm resources to broaden the genetic diversity of species. On the whole, Japonica landrace varieties in Yunnan, Guizhou and Sichuan had abundant genetic diversity. 6) The rule of cluster was obviously demonstrated that varieties from provinces which had similar geographical location could be divided into the same class. Cluster analysis among varieties from different rice cropping regions showed that the cluster rule was the same as varieties from different provinces. Above all, genetic relationship among varieties was correlated with geographical location.