Kenya Agricultural Research Institute (KARI), National Genebank, Nairobi, Kenya.
Theor Appl Genet. 2011 Mar;122(5):989-1004. doi: 10.1007/s00122-010-1504-5. Epub 2010 Dec 14.
Understanding the extent and partitioning of diversity within and among crop landraces and their wild/weedy relatives constitutes the first step in conserving and unlocking their genetic potential. This study aimed to characterize the genetic structure and relationships within and between cultivated and wild sorghum at country scale in Kenya, and to elucidate some of the underlying evolutionary mechanisms. We analyzed at total of 439 individuals comprising 329 cultivated and 110 wild sorghums using 24 microsatellite markers. We observed a total of 295 alleles across all loci and individuals, with 257 different alleles being detected in the cultivated sorghum gene pool and 238 alleles in the wild sorghum gene pool. We found that the wild sorghum gene pool harbored significantly more genetic diversity than its domesticated counterpart, a reflection that domestication of sorghum was accompanied by a genetic bottleneck. Overall, our study found close genetic proximity between cultivated sorghum and its wild progenitor, with the extent of crop-wild divergence varying among cultivation regions. The observed genetic proximity may have arisen primarily due to historical and/or contemporary gene flow between the two congeners, with differences in farmers' practices explaining inter-regional gene flow differences. This suggests that deployment of transgenic sorghum in Kenya may lead to escape of transgenes into wild-weedy sorghum relatives. In both cultivated and wild sorghum, genetic diversity was found to be structured more along geographical level than agro-climatic level. This indicated that gene flow and genetic drift contributed to shaping the contemporary genetic structure in the two congeners. Spatial autocorrelation analysis revealed a strong spatial genetic structure in both cultivated and wild sorghums at the country scale, which could be explained by medium- to long-distance seed movement.
了解作物地方品种及其野生/杂草近缘种内和种间多样性的程度和分布，是保护和挖掘其遗传潜力的第一步。本研究旨在在肯尼亚国家尺度上对栽培和野生高粱的遗传结构和种间关系进行分析，并阐明一些潜在的进化机制。我们共分析了 439 个个体，其中包括 329 个栽培高粱和 110 个野生高粱，使用了 24 个微卫星标记。我们在所有个体和位点共观察到 295 个等位基因，其中在栽培高粱基因库中检测到 257 个不同等位基因，在野生高粱基因库中检测到 238 个等位基因。我们发现，野生高粱基因库的遗传多样性显著高于其驯化的对应基因库，这反映了高粱的驯化伴随着遗传瓶颈。总的来说，我们的研究发现栽培高粱与其野生祖先之间存在密切的遗传亲缘关系，且作物与野生亲缘关系的分化程度在不同的栽培区有所不同。观察到的遗传亲缘关系可能主要是由于两者之间的历史和/或当代基因流，而农民的实践差异解释了区域间基因流的差异。这表明，在肯尼亚部署转基因高粱可能导致转基因逃逸到野生杂草高粱的近缘种中。在栽培和野生高粱中，遗传多样性主要沿地理水平而不是农业气候水平结构。这表明基因流和遗传漂变有助于塑造这两个近缘种的当代遗传结构。空间自相关分析显示，在国家尺度上，栽培和野生高粱都存在强烈的空间遗传结构，这可以用中长距离的种子传播来解释。
