Table1_Discovering useful genetic variation in the seed parent gene pool for sorghum improvement.xlsx

Multi-parent populations contain valuable genetic material for dissecting complex, quantitative traits and provide a unique opportunity to capture multi-allelic variation compared to the biparental populations. A multi-parent advanced generation inter-cross (MAGIC) B-line (MBL) population composed of 708 F6 recombinant inbred lines (RILs), was recently developed from four diverse founders. These selected founders strategically represented the four most prevalent botanical races (kafir, guinea, durra, and caudatum) to capture a significant source of genetic variation to study the quantitative traits in grain sorghum [Sorghum bicolor (L.) Moench]. MBL was phenotyped at two field locations for seven yield-influencing traits: panicle type (PT), days to anthesis (DTA), plant height (PH), grain yield (GY), 1000-grain weight (TGW), tiller number per meter (TN) and yield per panicle (YPP). High phenotypic variation was observed for all the quantitative traits, with broad-sense heritabilities ranging from 0.34 (TN) to 0.84 (PH). The entire population was genotyped using Diversity Arrays Technology (DArTseq), and 8,800 single nucleotide polymorphisms (SNPs) were generated. A set of polymorphic, quality-filtered markers (3,751 SNPs) and phenotypic data were used for genome-wide association studies (GWAS). We identified 52 marker-trait associations (MTAs) for the seven traits using BLUPs generated from replicated plots in two locations. We also identified desirable allelic combinations based on the plant height loci (Dw1, Dw2, and Dw3), which influences yield related traits. Additionally, two novel MTAs were identified each on Chr1 and Chr7 for yield traits independent of dwarfing genes. We further performed a multi-variate adaptive shrinkage analysis and 15 MTAs with pleiotropic effect were identified. The five best performing MBL progenies were selected carrying desirable allelic combinations. Since the MBL population was designed to capture significant diversity for maintainer line (B-line) accessions, these progenies can serve as valuable resources to develop superior sorghum hybrids after validation of their general combining abilities via crossing with elite pollinators. Further, newly identified desirable allelic combinations can be used to enrich the maintainer germplasm lines through marker-assisted backcross breeding.

多亲群体是解析复杂数量性状的珍贵遗传材料，相较双亲亲本群体，其独特优势在于能够捕获多等位基因变异。本研究近期构建了一套由4个多样性亲本衍生的多亲高级互交（Multi-parent Advanced Generation Inter-Cross, MAGIC）保持系（B-line, MBL）群体，该群体包含708个F6代重组自交系（Recombinant Inbred Lines, RILs）。该研究所选用的4个亲本均经过策略性筛选，分别代表了粒用高粱[Sorghum bicolor (L.) Moench]中4种最主流的植物学变种（kafir、guinea、durra与caudatum），旨在捕获充足的遗传变异以开展粒用高粱数量性状研究。

研究团队在2个田间试验点对MBL群体开展了7个产量相关性状的表型鉴定，包括穗型（Panicle Type, PT）、抽穗天数（Days to Anthesis, DTA）、株高（Plant Height, PH）、籽粒产量（Grain Yield, GY）、千粒重（1000-grain Weight, TGW）、每米分蘖数（Tiller Number per Meter, TN）以及单穗产量（Yield per Panicle, YPP）。所有数量性状均表现出较高的表型变异，其广义遗传力范围为0.34（TN）至0.84（PH）。

采用多样性阵列技术（Diversity Arrays Technology, DArTseq）对整个群体进行基因分型，共获得8800个单核苷酸多态性（Single Nucleotide Polymorphism, SNPs）标记。筛选得到3751个多态性且质量合格的SNP标记，结合表型数据开展全基因组关联分析（Genome-Wide Association Studies, GWAS）。利用2个试验点重复试验的最佳线性无偏预测（Best Linear Unbiased Prediction, BLUP）值，本研究共鉴定得到与7个性状相关的52个标记-性状关联（Marker-Trait Association, MTAs）。同时，基于影响产量相关性状的株高位点（Dw1、Dw2与Dw3），筛选得到了优良等位基因组合。此外，在1号染色体（Chr1）与7号染色体（Chr7）上各鉴定得到1个与产量性状相关的新型标记-性状关联，且该关联不受矮化基因影响。

进一步开展多变量自适应收缩分析，共鉴定得到15个具有多效性的标记-性状关联。最终筛选得到5个表现最优的MBL后代株系，其均携带优良等位基因组合。由于MBL群体的构建初衷即为捕获保持系（B-line）种质的丰富遗传多样性，因此这些后代株系在与优良恢复系杂交验证其一般配合力后，可作为培育优质高粱杂交种的珍贵遗传资源。此外，新鉴定得到的优良等位基因组合可通过标记辅助回交育种，用于扩充保持系种质资源库。