A test of taxonomic predictivity: resistance to the Colorado potato beetle in wild relatives of cultivated potato.

Wild relatives of potato offer a tremendous germplasm resource for breeders. Because the germplasm base of potato is so broad and diverse, we have undertaken a series of studies to determine whether we can predict the distribution of valuable genes in wild Solanum species based on taxonomic or biogeographic data. This is the third study in the series. Resistance to defoliation by Colorado potato beetle, Leptinotarsa decemlineata Say, larvae was evaluated in 156 accessions of 41 wild Solanum species. The highest frequencies of resistant accessions were found in diploid species with an endosperm balance number of 1. In contrast to previous studies on resistance to foliar fungal pathogens, there was little variability in defoliation scores among plants within an accession and among accessions within a species, at least for the most resistant species. There was no strong association of Colorado potato beetle resistance in wild potato species to biogeographic data. Resistance was confirmed in species previously characterized by high levels of glycoalkaloids or dense glandular trichomes. However, we have identified additional species with resistance to the Colorado potato beetle. Mechanisms of resistance are being studied in these species and attempts will be made to introgress them into the cultivated potato.