Massive Sorghum Collection Genotyped with SSR Markers to Enhance Use of Global Genetic Resources

Large ex situ collections require approaches for sampling manageable amounts of germplasm for in-depth characterization and use. We present here a large diversity survey in sorghum with 3367 accessions and 41 reference nuclear SSR markers. Of 19 alleles on average per locus, the largest numbers of alleles were concentrated in central and eastern Africa. Cultivated sorghum appeared structured according to geographic regions and race within region. A total of 13 groups of variable size were distinguished. The peripheral groups in western Africa, southern Africa and eastern Asia were the most homogeneous and clearly differentiated. Except for Kafir, there was little correspondence between races and marker-based groups. Bicolor, Caudatum, Durra and Guinea types were each dispersed in three groups or more. Races should therefore better be referred to as morphotypes. Wild and weedy accessions were very diverse and scattered among cultivated samples, reinforcing the idea that large gene-flow exists between the different compartments. Our study provides an entry to global sorghum germplasm collections. Our reference marker kit can serve to aggregate additional studies and enhance international collaboration. We propose a core reference set in order to facilitate integrated phenotyping experiments towards refined functional understanding of sorghum diversity.大型迁地保存的高粱种质资源库需要合理的采样策略，以获取适量种质资源用于深度鉴定与利用。本研究针对高粱开展大规模多样性调查，共纳入3367份种质资源与41个核基因组参考简单序列重复（Simple Sequence Repeat, SSR）标记。每个位点平均包含19个等位基因，其中等位基因数量最多的类群集中分布于中非与东非地区。栽培高粱的群体结构依地理区域及区域内的类群而分化，本研究共划分出13个大小各异的类群。分布于西非、南非与东亚的边缘类群遗传均一性最高，且与其他类群分化最为显著。除卡佛尔（Kafir）类群外，栽培类群与基于分子标记划分的类群之间几乎不存在对应关系。双色（Bicolor）、卡丹姆（Caudatum）、道格拉斯（Durra）与几内亚（Guinea）型高粱均分散分布于3个及以上的类群中，因此这些栽培类群更适合被称为形态型（morphotypes）。野生与杂草型种质资源具有极高的遗传多样性，且分散分布于栽培种质样本中，这进一步证实不同种质类群间存在广泛的基因交流。本研究为全球高粱种质资源库的整合利用提供了切入点，所开发的参考标记套装可用于整合后续相关研究，助力国际科研合作。我们建议构建一套核心参考种质集，以推动整合型表型鉴定实验的开展，从而深化对高粱遗传多样性的功能认知。