Glycoalkaloid content inSolanum species and hybrids from a breeding program for resistance to late blight (Phytophthora infestans)

As part of an effort to study the relationship between the “glycoalkaloid trait” and genetic resistance to late blight (Phytophthora infestans), glycoalkaloid content in tuber and foliar tissues from a wide genetic background withinSolanum, includingS. demissum, S. iopetalum and 15 hybrids selected from a backcrossing breeding scheme was determined. Analysis of variance indicated significant genotypic effect on total glycoalkaloid, solanidine, α-solanine, and α-chaconine content in both tubers and leaves. Tubers from wild potato species commonly contain glycoalkaloids in concentrations that exceed international health regulations for human consumption (20 mg/100 g fresh weight). In this study,S. demissum andS. iopetalum were highest in total tuber glycoalkaloids among all materials tested, with 70.4 and 76.2 mg/100 g fresh weight, respectively. In contrast, both commercial cultivars had the lowest concentration, both below the safety limit. Solanine was more abundant than chaconine in all but one genotype. All hybrids were intermediate to low in total glycoalkaloids. Except for the two wild species, glycoalkaloid concentration in leaves of all genotypes studied was at least twice that in tubers, with glycosylated forms accounting for more than 80% total glycoalkaloid content. Correlation between tuber and foliage alkaloids was poor. In view of the observed field resistance to late blight, it was concluded that tuber glycoalkaloid content may not be responsible for such resistance.