Key Laboratory of Southern Rice Innovation and Improvement, Ministry of Agriculture and Rural Affairs, Hunan Engineering Laboratory of Disease and Pest Resistant Rice Breeding, Yuan Longping High-Tech Agriculture Co., Ltd., Changsha, 410128, China.
State Key Laboratory of Hybrid Rice, Hunan Hybrid Rice Research Center, Changsha, 410125, China.
Sci Rep. 2021 Mar 15;11(1):6053. doi: 10.1038/s41598-021-85324-0.
Cadmium (Cd) contamination of rice is a serious food safety issue that has recently been gaining significant public attention. Therefore, reduction of Cd accumulation in rice grains is an important objective of rice breeding. The use of favourable alleles of Cd accumulating genes using marker-assisted selection (MAS) is theoretically feasible. In this study, we validated a segment covering OsHMA3-OsNramp5-OsNramp1 on chromosome 7 of japonica for establishing low-cadmium accumulating indica rice variety. The OsHMA3-OsNramp5-OsNramp1 haplotype significantly decreased grain Cd concentration in middle-season indica genetic background. The improved 9311 carrying the OsHMA3-OsNramp5-OsNramp1 haplotype with recurrent parent genome recovery of up to 91.6% resulted in approximately 31.8% decrease in Cd accumulation in the grain and with no penalty on yield. There is a genetic linkage-drag between OsHMA3-OsNramp5-OsNramp1 and the gene conditioning heading to days (HTD) in the early-season indica genetic background. Because the OsHMA3-OsNramp5-OsNramp1-Ghd7 haplotype significantly increases grain Cd concentration and prolongs growth duration, the linkage-drag between OsHMA3-OsNramp5-OsNramp1 and Ghd7 should be broken down by large segregating populations or gene editing. A novel allele of OsHMA3 was identified from a wide-compatibility japonica cultivar, the expression differences of OsNramp1 and OsNramp5 in roots might contribute the Cd accumulating variation between japonica and indica variety.
镉（Cd）污染大米是一个严重的食品安全问题，最近引起了公众的广泛关注。因此，减少大米中镉的积累是水稻育种的一个重要目标。利用有利的镉积累基因等位基因进行标记辅助选择（MAS）在理论上是可行的。在这项研究中，我们验证了位于第 7 号染色体上的粳稻 OsHMA3-OsNramp5-OsNramp1 区段，用于建立低镉积累籼稻品种。OsHMA3-OsNramp5-OsNramp1 单倍型显著降低了中季籼稻遗传背景下的籽粒镉浓度。携带 OsHMA3-OsNramp5-OsNramp1 单倍型的改良 9311，其轮回亲本基因组回收率高达 91.6%，导致籽粒镉积累减少约 31.8%，而产量没有损失。在早季籼稻遗传背景下，OsHMA3-OsNramp5-OsNramp1 与控制抽穗期的基因（HTD）之间存在遗传连锁拖曳。由于 OsHMA3-OsNramp5-OsNramp1-Ghd7 单倍型显著增加了籽粒镉浓度并延长了生长时间，因此应该通过大分离群体或基因编辑打破 OsHMA3-OsNramp5-OsNramp1 与 Ghd7 之间的连锁拖曳。从广亲和粳稻品种中鉴定到一个新的 OsHMA3 等位基因，根中 OsNramp1 和 OsNramp5 的表达差异可能导致了粳稻和籼稻品种之间镉积累的变异。
