Abstract
A good understanding of the dynamics of host/pathogen interactions and of the factors that shape the spatial distribution of resistance genes is a prerequisite of metapopulation dynamic management of resistance genes. We studied the diversity and spatial structure of natural populations of common bean (Phaseolus vulgaris) for resistance to Colletotrichum lindemuthianum, the causal agent of anthracnose. This study was carried out in Mexico and Argentina both at the phenotypic level and at the molecular level for two families of resistance gene candidates (RGCs). Using a simulation model, we also investigated the effects of migration and selection on the spatial structure of resistance phenotypes in a metapopulation for two genetic determinisms of the interaction (gene-for-gene and matching allele). Our results showed a differentiation between the countries for all the markers and indicated that the RGC, polymorphic in both countries, do not behave as neutral markers. Comparison of the diversities for resistance to strains isolated from wild or cultivated plants suggested that, although there is local adaptation of C. lindemuthianum between the two countries, the coevolution process seems to occur at a very local scale with the maintenance of resistances to allopatric strains, a result consistent with simulations of the models.