Identification of epistatic interaction affecting glycoalkalid content in tubers of tetraploid potato (Solanum tuberosum L.)

Glycoalkaloids are secondary metabolites characterised by an undesirable taste, and known to be toxic when consumed in large quantities. Their content in potato tubers should therefore be selected against and DNA markers can significantly facilitate such a process. This study was designed to describe the genetic control of the total content of glycoalkaloids (TGA) in the potato tuber and to enhance the development of DNA markers. A segregating population was constructed from tetraploid potato clones, which were characterised by divergent TGA-content. The population had a high-TGA parent, LT7, and a low-TGA parent, NT8. We used 342 Inter-Simple Sequence Repeat (ISSR) single primers or two such primer combinations and 36 Cleaved Amplified Polymorphic Sequence (CAPS) primer pairs, digested with various restriction enzymes, to amplify random PCR products. Parental clones of both populations were used to identify polymorphic PCR products for further linkage analyses with TGA-content. In these analyses, one single ISSR marker was found to be significantly associated with TGA-content. A multiple regression analysis was also carried out using a 'stepwise' procedure. In this regression analysis TGA-content was the dependent variable whereas the polymorphic PCR products and all possible two-way interactions among them were the independent variables. The resulting best model consisted of an interaction between two loci in addition to a single locus effect. This interaction suggests that the expression of TGA-content is partially modulated by two interacting loci.