Table3_Distribution characteristics of selenium, cadmium and arsenic in rice grains and their genetic dissection by genome-wide association study.XLSX

High selenium (Se) and low cadmium (Cd) and arsenic (As) contents in rice grains were good for human health. The genetic basis and relationship of Se, Cd and As concentrations in rice grains are still largely unknown. In the present study, large variations were observed in Se, Cd and As concentrations in brown and milled rice in normal and Se treatment conditions in 307 rice accessions from 3K Rice Genomes Project. Se fertilizer treatment greatly increased Se concentrations but had no obvious changes in concentrations of Cd and As both in brown and milled rice. Total of 237 QTL were identified for Se, Cd and As concentrations in brown and milled rice in normal and Se treatment conditions as well as ratio of concentrations under Se treatment to normal conditions. Only 19 QTL (13.4%) were mapped for concentrations of Se and Cd, Se and As, and Se, Cd and As in the same or adjacent regions, indicating that most Se concentration QTL are independent of Cd and As concentration QTL. Forty-three favorable alleles were identified for 40 candidate genes by gene-based association study and haplotype analysis in 14 important QTL regions. Se-enriched rice variety will be developed by pyramiding favorable alleles at different Se QTL and excluding undesirable alleles at Cd and As QTL, or combining favorable alleles at Se QTL with the alleles at Se-sensitive QTL by marker-assisted selection.

稻米籽粒中高硒（Se）、低镉（Cd）与低砷（As）含量对人体健康有益。目前学界对稻米中硒、镉、砷含量的遗传基础及其相互关联仍知之甚少。本研究以3000份水稻基因组计划（3K Rice Genomes Project）中的307份水稻种质为材料，在正常培养与硒处理两种条件下，检测了糙米与精米的硒、镉、砷含量，发现三者均存在较大变异。施加硒肥可显著提升稻米的硒含量，但对糙米与精米中的镉、砷含量无明显影响。本研究共鉴定出237个数量性状位点（QTL），涵盖正常与硒处理条件下糙米、精米的硒、镉、砷含量，以及硒处理与正常条件下的含量比值。其中仅19个QTL（占比13.4%）同时或相邻定位在调控硒与镉、硒与砷、或硒/镉/砷含量的区域，这表明绝大多数调控硒含量的QTL与调控镉、砷含量的QTL相互独立。通过基于基因的关联分析与单倍型分析，本研究在14个关键QTL区域内，为40个候选基因鉴定出43个有利等位基因。未来可通过标记辅助选择，聚合不同硒含量QTL的有利等位基因并剔除镉、砷含量QTL的不利等位基因，或将硒含量QTL的有利等位基因与硒敏感QTL的等位基因相结合，培育富硒水稻品种。