Structure of genetic diversity in the two major gene pools of common bean (Phaseolus vulgaris L., Fabaceae) |
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Authors: | Myounghai Kwak Paul Gepts |
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Institution: | (1) Department of Plant Sciences/MS1, Section of Crop and Ecosystem Sciences, University of California, 1 Shields Avenue, Davis, CA 95616-8780, USA |
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Abstract: | Domesticated materials with well-known wild relatives provide an experimental system to reveal how human selection during
cultivation affects genetic composition and adaptation to novel environments. In this paper, our goal was to elucidate how
two geographically distinct domestication events modified the structure and level of genetic diversity in common bean. Specifically,
we analyzed the genome-wide genetic composition at 26, mostly unlinked microsatellite loci in 349 accessions of wild and domesticated
common bean from the Andean and Mesoamerican gene pools. Using a model-based approach, implemented in the software STRUCTURE,
we identified nine wild or domesticated populations in common bean, including four of Andean and four of Mesoamerican origins.
The ninth population was the putative wild ancestor of the species, which was classified as a Mesoamerican population. A neighbor-joining
analysis and a principal coordinate analysis confirmed genetic relationships among accessions and populations observed with
the STRUCTURE analysis. Geographic and genetic distances in wild populations were congruent with the exception of a few putative
hybrids identified in this study, suggesting a predominant effect of isolation by distance. Domesticated common bean populations
possessed lower genetic diversity, higher F
ST, and generally higher linkage disequilibrium (LD) than wild populations in both gene pools; their geographic distributions
were less correlated with genetic distance, probably reflecting seed-based gene flow after domestication. The LD was reduced
when analyzed in separate Andean and Mesoamerican germplasm samples. The Andean domesticated race Nueva Granada had the highest
F
ST value and widest geographic distribution compared to other domesticated races, suggesting a very recent origin or a selection
event, presumably associated with a determinate growth habit, which predominates in this race.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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