Differences in Cd-tolerance of rice and screening for Cd low-accumulation rice germplasm resources

To develop genetic materials for breeding Cd-safe rice cultivars, the difference in Cd tolerance among rice parent materials were compared, and low Cd accumulation rice germplasms identified. The characteristics of growth and Cd accumulation of 145 rice parent materials were studied by using hydroponic method. Rice germplasms with low Cd accumulation were also identified based on Cd tolerance indices and Cd concentration. The results indicated that while dry weight (DW) and plant height (PH) of tested rice materials were inhibited on different extents under the stress of Cd ions, root lengths and root-to-shoot ratios were increased. Maximum Cd concentration and accumulation were 2.79 and 6.45 times the minimum of the restorer line materials, respectively. Similarity, maximum Cd concentration and accumulation were 2.00 and 2.98 times the minimum of the maintainer line materials, respectively. Based on Cd tolerance identification, the restorer line and maintainer line materials were divided into five groups, respectively. A total of 13 restorer line materials with low Cd accumulation were obtained. They were "MR183", "MR86", "R047", "R364", "Luhui 602", "Luhui 615", "Luhui 17", "GR548/M63//527_2", "R18", "Chenghui 838", "GR548/M63//M63_5", "GRL17/IRBN95-199_3" and "GRL17/ATTP//L17_3". Also an additional 2 maintainer line materials ("Yuxiang B" and "D62B") low in Cd accumulation were obtained. Among high Cd tolerant materials, maximum Cd concentration and accumulation were 1.97 and 2.03 times the minimum of the restorer line materials, respectively. Furthermore, maximum Cd concentration and accumulation were 1.43 and 1.40 times the minimum of the maintainer line materials, respectively. No significant difference was noted in Cd concentration and accumulation between the restorer and maintainer line materials. Identification Cd-safe rice germplasms and breeding Cd-safe rice cultivars were critical for Cd risk for human health.