Papa R, Acosta J, Delgado-Salinas A, Gepts P
Department of Plant Sciences, Section of Crop and Ecosystem Sciences, University of California, Mailstop 1, Davis, CA 95616-8780, USA.
Theor Appl Genet. 2005 Oct;111(6):1147-58. doi: 10.1007/s00122-005-0045-9. Epub 2005 Oct 11.
Lack of introgression or divergent selection may be responsible for the maintenance of phenotypic differences between sympatric populations of crops and their wild progenitors. To distinguish between these hypotheses, amplified fragment length polymorphism markers were located on a molecular linkage map of Phaseolus vulgaris relative to genes for the domestication syndrome and other traits. Diversity for these same markers was then analyzed in two samples of wild and domesticated populations from Mesoamerica. Differentiation between wild and domesticated populations was significantly higher in parapatric and allopatric populations compared to sympatric populations. It was also significantly higher near genes for domestication compared to those away from these genes. Concurrently, the differences in genetic diversity between wild and domesticated populations were strongest around such genes. These data suggest that selection in the presence of introgression appears to be a major evolutionary factor maintaining the identity of wild and domesticated populations in sympatric situations. Furthermore, alleles from domesticated populations appear to have displaced alleles in sympatric wild populations, thus leading to a reduction in genetic diversity in such populations. These results also provide a possible experimental framework for assessing the long-term risk of transgene escape and the targeting of transgenes inside the genome to minimize the survival of these transgenes into wild populations following introduction by gene flow.
缺乏基因渗入或趋异选择可能是导致作物同域分布种群与其野生近缘种之间表型差异得以维持的原因。为区分这些假说，相对于驯化综合征及其他性状的基因，扩增片段长度多态性标记被定位到菜豆的分子连锁图谱上。随后，对来自中美洲的野生和驯化种群的两个样本中相同标记的多样性进行了分析。与同域分布种群相比，异域分布和异地分布种群中野生和驯化种群之间的分化显著更高。与远离驯化基因的区域相比，在驯化基因附近的分化也显著更高。同时，野生和驯化种群之间的遗传多样性差异在这类基因周围最为明显。这些数据表明，在存在基因渗入的情况下进行选择似乎是在同域分布情况下维持野生和驯化种群特性的主要进化因素。此外，驯化种群的等位基因似乎已取代了同域分布野生种群中的等位基因，从而导致这类种群的遗传多样性降低。这些结果还为评估转基因逃逸的长期风险以及将转基因定位在基因组内部以尽量减少这些转基因通过基因流引入后在野生种群中存活的可能性提供了一个可能的实验框架。
