Additional Isozyme Loci in Tuber-Bearing Solanums: Inheritance and Linkage Relationships

Horizontal starch gel electrophoresis was used to perform genetic analysis to confirm the inheritance of various isozyme loci and report on additional loci in diploid Solanum species. Aps-1, Dia-1, and ldh-1 were identified as new loci, and tetrasomic segregation was reported at the tetraploid level for Mdh-2. Of 15 loci studied, distorted segregations were observed in five diploid test crosses involving the Got-1, ldh-1, Pgi-1, and Adh-1 loci. In these cases, four of the five parents were of interspecific origin; the family segregating for Adh-1 was the exception. Utilizing various clones and interspecific combinations between S. phureja, S. tuberosum, and S. chacoense, further test crosses were made to determine linkage relationships between these isozyme loci and the yellow tuber flesh gene (Y). Two linkages were detected among these markers. Estimates of the ldh-1/Sdh-1 linkage ranged from 10.4 map units (m.u.) to 36.8 m.u., whereas a tight linkage was confirmed for Prx-2/Prx-3 (0.6 m.u.). Comparing putative homologous loci for the ldh-1/Sdh-1 linkage implies some conservation since the divergence of Lycoperison, Solanum, and, to a degree, Capsicum. As a result of codominant expression, these isozyme markers provide new opportunities for further genetic studies of tuber-bearing Solanums.