Table_1_QTL Mapping Using a High-Density Genetic Map to Identify Candidate Genes Associated With Metribuzin Tolerance in Hexaploid Wheat (Triticum aestivum L.).xlsx

Tolerance to metribuzin, a broad-spectrum herbicide, is an important trait for weed control in wheat breeding. However, the genetics of metribuzin tolerance in relation to the underlying quantitative trait loci (QTL) and genes is limited. This study developed F8 recombinant inbred lines (RILs) from a cross between a highly resistant genotype (Chuan Mai 25) and highly susceptible genotype (Ritchie), which were used for QTL mapping of metribuzin tolerance. Genotyping was done using a diversity arrays technology sequencing (DArTseq) platform, and phenotyping was done in controlled environments. Herbicide tolerance was measured using three traits, visual score (VS), reduction of chlorophyll content (RCC), and mean value of chlorophyll content for metribuzin-treated plants (MCC). A high-density genetic linkage map was constructed using 2,129 DArTseq markers. Inclusive composite interval mapping (ICIM) identified seven QTL, one each on chromosomes 2A, 2D, 3A, 3B, 4A, 5A, and 6A. Three major QTL—Qrcc.uwa.2AS, Qrcc.uwa.5AL, and Qrcc.uwa.6AL—explained 11.39%, 11.06%, and 11.45% of the phenotypic variation, respectively. The 5A QTL was further validated using kompetitive allele-specific PCR (KASP) assays in an F3 validation population developed from Chuan Mai 25 × Dagger. Blasting the single-nucleotide polymorphisms (SNPs) flanking the QTL in the wheat reference genome RefV1.0 revealed SNP markers within or very close to annotated genes which could be candidate genes responsible for metribuzin tolerance. Most of the candidate genes were related to metabolic detoxification, especially those of P450 pathway and xenobiotic transmembrane transporter activity, which are reportedly key molecules responsible for herbicide tolerance. This study is the first to use specially developed populations to conduct QTL mapping on the metribuzin tolerance trait. The three major QTL and candidate genes identified in this study could facilitate marker-assisted metribuzin breeding in wheat. The QTL could be fine-mapped to locate the genes responsible for metribuzin tolerance, which could be introgressed into elite wheat cultivars.

嗪草酮（metribuzin）作为一种广谱除草剂，其耐受性是小麦杂草防控育种中的关键性状。但目前针对嗪草酮耐受性的遗传学解析，尤其是其关联的数量性状位点（quantitative trait loci, QTL）与功能基因的研究仍较为匮乏。本研究以高抗嗪草酮的川麦25（Chuan Mai 25）与高感材料Ritchie为亲本杂交，构建F8代重组自交系（recombinant inbred lines, RILs）群体，并将其用于嗪草酮耐受性的QTL定位研究。基因型鉴定采用多样性阵列技术测序（diversity arrays technology sequencing, DArTseq）平台完成，表型鉴定则在可控环境条件下开展。本研究通过3个表型指标量化除草剂耐受性：视觉评分（visual score, VS）、叶绿素含量降低率（reduction of chlorophyll content, RCC），以及嗪草酮处理植株的叶绿素含量平均值（mean value of chlorophyll content for metribuzin-treated plants, MCC）。研究团队利用2129个DArTseq标记构建了高密度遗传连锁图谱。采用完备复合区间作图法（inclusive composite interval mapping, ICIM）进行分析，共检测到7个QTL，分别分布于2A、2D、3A、3B、4A、5A及6A染色体上。其中3个主效QTL（Qrcc.uwa.2AS、Qrcc.uwa.5AL与Qrcc.uwa.6AL）分别解释了11.39%、11.06%与11.45%的表型变异。研究人员利用川麦25与Dagger杂交构建的F3验证群体，通过竞争性等位基因特异性PCR（kompetitive allele-specific PCR, KASP）标记，对5A染色体上的QTL进行了验证。将QTL侧翼的单核苷酸多态性（single-nucleotide polymorphisms, SNPs）与小麦参考基因组RefV1.0进行比对后发现，部分SNP标记位于注释基因内部或其邻近区域，这些基因可作为嗪草酮耐受性的候选基因。多数候选基因参与代谢解毒过程，尤其是细胞色素P450通路相关基因与外源性物质跨膜转运活性相关基因，已有研究表明这类分子是调控除草剂耐受性的关键因子。本研究为首次利用专门构建的群体开展嗪草酮耐受性性状的QTL定位研究。本研究鉴定的3个主效QTL与候选基因，可为小麦嗪草酮耐受性的分子标记辅助育种提供重要支撑。上述QTL可通过精细定位克隆其调控基因，并进一步将其导入优良小麦品种中。