籽粒镉低积累水稻地上部镉高积累遗传特性分析

农田土壤镉（Cd）污染日益严重，导致稻米Cd含量超标事件频繁出现，使粮食安全问题备受关注。因此，合理利用Cd污染农田、降低水稻籽粒Cd含量成为亟待解决的问题。籽粒Cd低积累水稻雅恢2816的地上部具有较强的Cd积累能力，研究旨在弄清其地上部Cd积累能力的遗传稳定性，进一步揭示控制该性状的遗传基础，为利用分子标记辅助选育地上部Cd富集能力强、籽粒Cd安全的水稻提供途径。以水稻雅恢2816和3个不同品种水稻分别组配获得的F₁为研究对象，分析地上部Cd积累相关性状的杂种优势。进一步以优势组合C268A/雅恢2816构建F₂作图群体，对地上部Cd积累相关性状进行QTL定位分析。结果表明：（1） F₁地上部Cd积累相关性状杂种优势明显，遗传稳定性强。地上部Cd积累相关性状属数量性状，F₂中/超亲分离现象明显。（2）在第4、6号染色体上共挖掘到1个控制水稻地上部生物量和3个控制地上部Cd积累量的QTL位点，分别为qSB-6、qSCdA-4、qSCdA-6-1和qSCdA-6-2，表型贡献率为10.6%—14.4%，且增效等位基因均来自雅恢2816。（3）地上部Cd积累量与地上部生物量、Cd含量，根、糙米的生物量、Cd积累量，根-地上部转移系数均呈极显著正相关，与地上部-籽粒转移系数呈极显著负相关，存在4个QTL集簇区Cl-4-1、Cl-6-1、Cl-6-2和Cl-6-3。（4）区间marker 04171-marker 04197控制着地上部生物量和Cd积累量，与控制糙米Cd含量的QTL不重叠。研究表明：籽粒Cd低积累水稻雅恢2816携带控制地上部Cd高积累的等位基因，可在世代间稳定遗传，QTL位点qSCdA-4、qSCdA-6-1、qSCdA-6-2是控制该性状的重要遗传基础，可为分子标记辅助选育地上部Cd高积累、籽粒Cd低积累水稻提供理论依据。

Pivotal genetic mechanisms of the shoot cadmium accumulation in a low grain cadmium-accumulating rice

Farmland soil is gradually polluted by cadmium (Cd), which leads to the excessive Cd concentration in grain. Food security has attracted much attention of people all over the world. Therefore, the utilization of Cd polluted farmland soil and reduction of the Cd concentration in grain have become an urgent issue to be resolved. Yahui2816, a low grain Cd-accumulating rice line with high shoot Cd-accumulation, is potential to achieve these goals simultaneously. The genetic stability of shoot Cd accumulation and the relevant genetic basis in Yahui 2816 was investigated in this study, providing an idea for molecular marker-assisted selection of low grain Cd-accumulating rice with high shoot Cd accumulation. Three types of F₁ hybrids were constructed by rice restorer line Yahui 2816 and three male sterile lines (Lu98A, 5406A and C268A) to analyze the heterosis of shoot Cd accumulation. The F₂ population was constructed by Yahui2816 and C268A. The F₁ population (constructed by Yahui2816 and C268A) showed a distinct advantage and thus met the basic requirement of quantitative trait locus (QTL) analysis of phenotypic isolation. Furthermore, the F₂ was used to analyze the QTLs of shoot Cd accumulation combined with the genetic linkage map. The results revealed that:(1) F₁ hybrids showed a good heterosis phenomenon of shoot Cd accumulation, indicating Yahui2816 had strong genetic stability. Meanwhile, a mid-/super-parent segregation was observed in F₂ population. (2) A QTL controlling shoot biomass (qSB-6) and three QTLs controlling shoot Cd accumulation (qSCdA-4, qSCdA-6-1 and qSCdA-6-2) were detected on chromosome 4 and 6, explaining 10.6%-14.4% of the phenotypic variance in the shoot Cd accumulation of the F₂ population. (3) Shoot Cd accumulation showed significantly positive correlations with shoot biomass and Cd concentration, root and grain biomass and Cd accumulation, transfer factor of Cd to shoot, and a negative correlation with transfer factor of Cd to grain. In addition, there were 4 overlap regions (Cl-4-1, Cl-6-1, Cl-6-2 and Cl-6-3) controlling two or more traits at the same time. (4) Marker 04171-marker 04197 controlled shoot biomass and Cd accumulation simultaneously and did not overlap with the QTLs controlling grain Cd concentration. In conclusion, Yahui2816 carried an allele which can enhance the ability of shoot Cd accumulation, and its related traits could be stably inherited from generation to generation. QTLs (qSCdA-4, qSCdA-6-1 and qSCdA-6-2) controlling shoot Cd accumulation were beneficial for molecular marker-assisted breeding of rice with high shoot Cd accumulation and low grain Cd accumulation.