A test of taxonomic and biogeographic predictivity: resistance to soft rot in wild relatives of cultivated potato.

The concept that traits should be associated with related organisms and that nearby populations of the same species are likely to be more similar to each other than to populations spread far apart has long been accepted. Consequently, taxonomic relationships and biogeographical data are commonly believed to have the power to predict the distribution of disease resistance genes among plant species. In this study, we test claims of such predictivity in a group of widely distributed wild potato species. There was no clear association between resistance to soft rot and taxonomic relationships. However, we have found some associations between resistance to soft rot and environmental data such as annual precipitation and annual mean temperature. In addition, we have noted that high levels of resistance are mostly found in species with high levels of phenotypic plasticity. The three most resistant species were Solanum paucijugum, S. brevicaule, and S. commersonii.