Table_1_Phenotypic Evaluation and Genetic Analysis of Seedling Emergence in a Global Collection of Wheat Genotypes (Triticum aestivum L.) Under Limited Water Availability.DOCX

The challenge in establishing an early-sown wheat crop in southern Australia is the need for consistently high seedling emergence when sowing deep in subsoil moisture (>10 cm) or into dry top-soil (4 cm). However, the latter is strongly reliant on a minimum soil water availability to ensure successful seedling emergence. This study aimed to: (1) evaluate 233 Australian and selected international wheat genotypes for consistently high seedling emergence under limited soil water availability when sown in 4 cm of top-soil in field and glasshouse (GH) studies; (2) ascertain genetic loci associated with phenotypic variation using a genome-wide association study (GWAS); and (3) compare across loci for traits controlling coleoptile characteristics, germination, dormancy, and pre-harvest sprouting. Despite significant (P < 0.001) environment and genotype-by-environment interactions within and between field and GH experiments, eight genotypes that included five cultivars, two landraces, and one inbred line had consistently high seedling emergence (mean value > 85%) across nine environments. Moreover, 21 environment-specific quantitative trait loci (QTL) were detected in GWAS analysis on chromosomes 1B, 1D, 2B, 3A, 3B, 4A, 4B, 5B, 5D, and 7D, indicating complex genetic inheritance controlling seedling emergence. We aligned QTL for known traits and individual genes onto the reference genome of wheat and identified 16 QTL for seedling emergence in linkage disequilibrium with coleoptile length, width, and cross-sectional area, pre-harvest sprouting and dormancy, germination, seed longevity, and anthocyanin development. Therefore, it appears that seedling emergence is controlled by multifaceted networks of interrelated genes and traits regulated by different environmental cues.

澳大利亚南部早播小麦生产面临的核心挑战在于：当播于深层土壤水分区（>10厘米）或4厘米厚的干表土层时，需保障稳定的高幼苗出苗率（seedling emergence）。而针对干表土层的播种，其成功出苗强烈依赖最低土壤含水量保障。本研究旨在：(1) 在田间与温室（glasshouse, GH）试验中，针对4厘米厚表土层且土壤水分有限的种植条件，评估233份澳大利亚及精选国际小麦基因型（genotype）的稳定高幼苗出苗率表现；(2) 通过全基因组关联分析（genome-wide association study, GWAS）挖掘与表型变异相关的遗传位点；(3) 对比调控胚芽鞘（coleoptile）特性、发芽、休眠及穗发芽（pre-harvest sprouting）的性状相关遗传位点。尽管田间与温室试验内部及试验间均存在显著（P < 0.001）的环境效应及基因型-环境互作，仍有8份小麦基因型（含5个栽培品种、2个地方品种及1个自交系）在9个试验环境中均表现出稳定的高幼苗出苗率（平均出苗率>85%）。此外，通过GWAS分析在1B、1D、2B、3A、3B、4A、4B、5B、5D及7D染色体上共检测到21个环境特异性数量性状位点（quantitative trait loci, QTL），表明调控幼苗出苗的遗传机制具有复杂的多基因调控特性。我们将已知性状及单个基因的QTL定位到小麦参考基因组上，发现16个与幼苗出苗相关的QTL与胚芽鞘长度、宽度、横截面积、穗发芽、休眠、发芽、种子寿命（seed longevity）及花青素发育（anthocyanin development）相关的性状位点处于连锁不平衡（linkage disequilibrium）状态。综上可见，幼苗出苗受由不同环境信号调控的多基因互作与性状关联网络所控制。