Screening and analysis of cadmium-tolerant rice variety resources.

In order to find out the difference in cadmium tolerance of different rice varieties in central Hunan, 26 varieties of conventional rice, two-line hybrid rice and three-line hybrid rice were used as materials. The effects of cadmium stress（0.5 mmol/L）on germination percentage, germination index, vigor index, root length, bud length and fresh weight of root buds of rice seeds were studied by indoor bioassay. The results showed that cadmium stress had little effect on seed germination rate and germination index of different rice varieties, but had obvious effect on vigor index, root and bud growth, and the inhibitory effect of cadmium stress on root was significantly greater than that on bud. There were some differences in the mean values of six indexes among different types of rice varieties, but the differences were not significant. The tolerance responses of 26 varieties to cadmium stress were quite different. According to the cluster analysis of comprehensive effects of stress, they could be divided into three types: sensitive type, intermediate type and tolerant type. Among them, the sensitive rice varieties were Xiangwanxian 16, Y Liangyou 9918, C Liangyou 651 and Xin You 215, accounting for 15.38% of the total tested varieties; the tolerant varieties were Y Liangyou 1 and Neixiang 2128, accounting for 7.69% of the tested varieties; the other varieties fell within tolerant intermediate type, accounting for 76.92%.