The European Phaseolus coccineus L. landraces: population structure and adaptation, as revealed by of cpSSRs, nuSSRs and phenotypic analyses

Relatively few studies have analysed the genetic diversity of the runner bean through molecular markers. Here, we investigate the cytoplasmic diversity of 331 European domesticated accessions of the scarlet runner bean (Phaseolus coccineus L.) and a sample of 49 domesticated and wild accessions from Mesoamerica. For a subset of accessions, we compare the results obtained by chloroplast and nuclear microsatellite (SSR) analyses and those obtained by analyses for molecular markers and phenotypic traits. Our results suggest that both demographic and selective factors have roles in the shaping of the population genetic structure of the European runner bean. In particular, we infer the existence of a bottleneck following the expansion of the crop into Europe, and we deduce multiple domestication events for this species. We also observe an adaptive population differentiation in phenology across a latitudinal gradient, which suggests that selection led to the diversification of the runner bean in Europe. As could be expected, the botanical varieties albiflorus, bicolor and coccineus based solely on flower colour, cannot be distinguished based on chloroplast SSRs, nuclear SSRs or 12 quantitative traits.