Capturing genetic variation in crop wild relatives: an evolutionary approach

Crop wild relatives (CWRs) offer novel genetic resources for crop improvement. To assist in the urgent need to collect and conserve CWR germplasm, we advance here the concept of an ‘evolutionary’ approach. Central to this approach is the predictive use of spatial proxies of evolutionary processes (natural selection, gene flow, and genetic drift) to locate and capture genetic variation. As a means to help validate this concept, we screened wild-collected genotypes of woodland strawberry (Fragaria vesca) in a common garden. A quantitative genetics approach was then used to test the ability of two such proxies – mesoclimatic variation (a proxy of natural selection) and landscape isolation and geographic distance between populations (proxies of gene flow potential) – to predict spatial genetic variation in three quantitative traits (plant size, early season flower number, and flower frost tolerance). Our results indicated a significant but variable effect of mesoclimatic conditions in structuring genetic variation in the wild, in addition to other undetermined regional scale processes. As a proxy of gene flow potential, landscape isolation was also a likely determinant of observed patterns – as opposed to and regardless of geographic distance between populations. We conclude that harnessing proxies of adaptive and non-adaptive evolutionary processes could provide a robust and valuable means to identify genetic variation in CWRs. We thus advocate wider use of this approach amongst researchers, breeders, and practitioners, to expedite the capture and in situ conservation of genetic resources provided by crop wild relatives.