CIRAD, UMR AGAP, Avenue d'Agropolis, 34398, Montpellier, France.
Theor Appl Genet. 2011 Nov;123(7):1231-46. doi: 10.1007/s00122-011-1662-0. Epub 2011 Aug 3.
Gene flow between domesticated plants and their wild relatives is one of the major evolutionary processes acting to shape their structure of genetic diversity. Earlier literature, in the 1970s, reported on the interfertility and the sympatry of wild, weedy and cultivated sorghum belonging to the species Sorghum bicolor in most regions of sub-Saharan Africa. However, only a few recent surveys have addressed the geographical and ecological distribution of sorghum wild relatives and their genetic structure. These features are poorly documented, especially in western Africa, a centre of diversity for this crop. We report here on an exhaustive in situ collection of wild, weedy and cultivated sorghum assembled in Mali and in Guinea. The extent and pattern of genetic diversity were assessed with 15 SSRs within the cultivated pool (455 accessions), the wild pool (91 wild and weedy forms) and between them. F (ST) and R (ST) statistics, distance-based trees, Bayesian clustering methods, as well as isolation by distance models, were used to infer evolutionary relationships within the wild-weedy-crop complex. Firstly, our analyses highlighted a strong racial structure of genetic diversity within cultivated sorghum (F (ST) = 0.40). Secondly, clustering analyses highlighted the introgressed nature of most of the wild and weedy sorghum and grouped them into two eco-geographical groups. Such closeness between wild and crop sorghum could be the result of both sorghum's domestication history and preferential post-domestication crop-to-wild gene flow enhanced by farmers' practices. Finally, isolation by distance analyses showed strong spatial genetic structure within each pool, due to spatially limited dispersal, and suggested consequent gene flow between the wild and the crop pools, also supported by R (ST) analyses. Our findings thus revealed important features for the collection, conservation and biosafety of domesticated and wild sorghum in their centre of diversity.
基因流是塑造家养植物及其野生亲缘种遗传多样性结构的主要进化过程之一。20 世纪 70 年代的早期文献报道了在撒哈拉以南非洲的大多数地区，属于二色高粱种的野生、杂草和栽培高粱之间的可交配性和同域分布。然而，只有少数最近的调查研究了高粱野生亲缘种的地理和生态分布及其遗传结构。这些特征记录甚少，特别是在该作物的多样性中心西非。我们在此报告了在马里和几内亚进行的一次详尽的野生、杂草和栽培高粱的实地采集。利用 15 个 SSR 标记评估了栽培种（455 个品系）、野生种（91 种野生和杂草形式）和两者之间的遗传多样性程度和模式。利用 F（ST）和 R（ST）统计、基于距离的树、贝叶斯聚类方法以及距离隔离模型，推断了野生-杂草-作物复合体中的进化关系。首先，我们的分析突出了栽培高粱内部遗传多样性的强烈种族结构（F（ST）=0.40）。其次，聚类分析突出了大多数野生和杂草高粱的渐渗性质，并将它们分为两个生态地理群。野生和作物高粱之间的这种接近可能是高粱驯化历史和农民实践增强的后驯化作物向野生的基因流的结果。最后，距离隔离分析表明，由于空间扩散有限，每个群体内部都存在强烈的空间遗传结构，并暗示野生和作物群体之间存在基因流，这也得到了 R（ST）分析的支持。我们的研究结果揭示了在其多样性中心收集、保护和生物安全方面家养和野生高粱的重要特征。
