An international research project led by the CBGP group ‘Plant-virus interaction and co-evolution’, with the collaboration of researchers from French and Mexican institutions, shows how human management of plant populations strongly influences diversity and evolution of resistance to plant viruses. The focus of the study is the pathosystem potyviruses/chiltepín (a wild Mexican pepper)
Viruses cause plant diseases, whose severity is considered to increase under plant cultivation. Hence, it is highly relevant to understand the genetics of plant virus resistance, and its variation in wild and cultivated plants. Analyses of plant pathogen resistance have focussed on R proteins, which recognise pathogen molecules triggering defences according to a gene-for-gene interaction. Alternatively, infection may require the interaction of plant and pathogen molecules, mutations impairing this interaction resulting in recessive resistance according to a matching-alleles model. We analyse here the variation of a recessive resistance gene in wild and cultivated populations of a plant, focussing on chiltepin, a wild pepper currently undergoing incipient cultivation in Mexico. Thepvr2 gene encodes the translation initiation factor eIF4E1, which must interact with the viral VPg for potyvirus infection. A high genetic variation was found for pvr2/eIF4E1 but, at odds with reports for R genes, there was no evidence for selection of resistance in wild chiltepin populations. However, data supported selection for resistance in cultivated populations, in spite of no phenotypic differences between wild and cultivated plants, and similar potyvirus incidences. Results demonstrate that cultivation has profound effects on the diversity and evolution of resistance.