Resistance to late blight and soft rot in six potato progenies and glycoalkaloid contents in the tubers

Glycoalkaloids are anti-nutritional compounds commonly found in wild Solanum species used as resistance sources to major potato pathogens. It is therefore important for breeding purposes to know whether selecting for resistance using such species necessarily selects also for high glycoalkaloid contents in the tubers. To test this hypothesis, we used six partial progenies from crosses between Solanum tuberosum and accessions of S. andigena, S. berthaultii, S. phureja, and S. vernei to investigate the possible correlation between resistance to Phytophthora infestans and/or to Erwinia carotovora subsp. atroseptica and the concentration of glycoalkaloids in tubers. Concentrations of alpha-solanine and alpha-chaconine in the tubers segregated in each progeny, as did resistance to each pathogen. Some, but not all, clones from each progeny showed hypersensitive reactions to the isolate of P. infestans used. Furthermore, clones within each progeny also differed for components of partial resistance to R infestans, suggesting that all four wild species could be used as sources of both race-specific and partial resistance to late blight. With the exception of low, but statistically significant, correlations between concentration of alpha-solanine and two late blight resistance components (incubation period and spore production per unit lesion area) in progenies derived from S. vernei, and despite a trend towards higher glycoalkaloid concentrations in the tubers of the clones most resistant to soft rot within progenies derived from S. berthauttli and S. vernei, no consistent relationship between resistance to either disease and concentrations of a-solanine and/or a-chaconine was observed. These results indicate that neither race-specific nor partial resistance to late blight and soft rot in the accessions used as progenitors of resistance depend on high solanine or chaconine concentrations. These resistance sources could thus prove useful in breeding programs for improved behaviour against P. infestans and/or E. carotovora.