Abstract
The wild progenitor of common-bean has an exceptionally large distribution from northern Mexico to northwestern Argentina, unusual among crop wild progenitors. This research sought to document major events of range expansion that led to this distribution and associated environmental changes. Through the use of genotyping-by-sequencing (∼20,000 SNPs) and geographic information systems applied to a sample of 246 accessions of wild Phaseolus vulgaris, including 157 genotypes of the Mesoamerican, 77 of the southern Andean, and 12 of the Northern Peru–Ecuador gene pools, we identified five geographically distinct subpopulations. Three of these subpopulations belong to the Mesoamerican gene pool (Northern and Central Mexico, Oaxaca, and Southern Mexico, Central America and northern South America) and one each to the Northern Peru–Ecuador (PhI) and the southern Andean gene pools. The five subpopulations were distributed in different floristic provinces of the Neotropical seasonally dry forest and showed distinct distributions for temperature and rainfall resulting in decreased local potential evapotranspiration (PhI and southern Andes groups) compared with the two Mexican groups. Three of these subpopulations represent long-distance dispersal events from Mesoamerica into Northern Peru–Ecuador, southern Andes, and Central America and Colombia, in chronological order. Of particular note is that the dispersal to Northern Peru–Ecuador markedly predates the dispersal to the southern Andes (∼400 vs. ∼100 ky), consistent with the ancestral nature of the phaseolin seed protein and chloroplast sequences observed in the PhI group. Seed dispersal in common bean can be, therefore, described at different spatial and temporal scales, from localized, annual seed shattering to long‐distance, evolutionarily rare migration.
Highlights
Common bean (Phaseolus vulgaris) is one of the most important crops for human nutrition, being a source of proteins, vitamins, fibers, and essential micronutrients worldwide (Gepts et al 2008)
A third gene pool, from Northern Peru and Ecuador, only consists of wild populations (Gepts et al 1986; Debouck et al 1993). This gene pool is characterized by a specific phaseolin seed protein type (“I” phaseolin), which is ancestral based on the absence of tandem direct repeats in the phaseolin genes; the type I phaseolin is absent in the Mesoamerican and Andean gene pools (Kami et al 1995)
We developed a broad sample of wild P. vulgaris accessions, representing most of the extensive geographic distribution of this wild progenitor and used the GBS genotyping approach, which resulted in some 20,000 SNPs
Summary
Common bean (Phaseolus vulgaris) is one of the most important crops for human nutrition, being a source of proteins, vitamins, fibers, and essential micronutrients worldwide (Gepts et al 2008) This species belongs to a highly diversified genus that comprises approximately 70 different species, of which five of them have been domesticated (Freytag and Debouck 2002). Current knowledge highlights the presence of two distinct wild gene pools in common bean, in Mesoamerica and the southern Andes, which were domesticated independently (Gepts 1998; Kwak and Gepts 2009; Kwak et al 2009; Bitocchi et al 2013; Schmutz et al 2014; Vlasova et al 2016) These domesticated pools underwent local adaptations and diversified into landraces with distinct characteristics (Singh et al 1991; Chacon et al 2007). This gene pool is characterized by a specific phaseolin seed protein type (“I” phaseolin), which is ancestral based on the absence of tandem direct repeats in the phaseolin genes; the type I phaseolin is absent in the Mesoamerican and Andean gene pools (Kami et al 1995)
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