Inheritance study of tuber glycoalkaloids in a wild potato,Solanum chacoense bitter

Studies were made of segregating families from crosses between accessions of Solanumchacoense Bitter differing in steroid glycoalkaloids. The major glycoalkaloids were isolated from tubers and identified by thin-layer chromatography. Simple segregation ratios of 3:1 in an F₂ and 1:1 in backcrosses were obtained for the presence:absence of solanine, chaconine, and commersonine. To explain the simultaneous segregation of the three glycoalkaloids, we tentatively hypothesize that: (1) solanine and commersonine are determined by alternative codominant alleles at a single gene locus; (2) a major gene for chaconine segregates independently of the solanine/commersonine locus; and (3) a recessive gene linked with the commersonine allele is epistatic to the chaconine gene, causing the production of β-chaconine instead of the usual α-chaconine. The F₂ distribution could be fit to the ratio 3:6:3:1:2:1, seen as combining the 1:2:1 segregation of solanine: solanine + commersonine: commersonine and the 3:1 segregation of presence: absence of chaconine.