GENETIC-ANALYSIS OF PROTOPLAST CULTURABILITY IN SOLANUM-PHUREJA

Protoplast culturability, defined as the ability of a genotype to develop calli from cultured protoplasts, was studied in the diploid potato species, Solanum phureja Juz. and Buk. A protoplast non-culturable, androgenetically derived homozygous line, AM3-8, was crossed with a protoplast culturable selection, NBP2. Seven F1 plants were randomly selected and tested for protoplast culturability. All these F1 plants were capable of forming abundant protoplast calli (p-calli). F2 progeny was produced by crossing two randomly selected F1 individuals (F(1)21 x F(1)37). Segregation for protoplast culturability occurred in the F2 generation: among twenty randomly selected F2 plants, twelve were protoplast culturable, and eight non-culturable. Backcrossing F(1)37 to both AM3-8 and NBP2 generated BCA and BCN populations. Eight plants from each backcross were randomly chosen and tested for protoplast culturability. All eight plants from the backcross to NBP2 were protoplast-culturable, whereas only two plants from the backcross to AM3-8 were culturable. Variation (3-31%) in protoplast plating efficiency, estimated 7 days after protoplast isolation, was observed among culturable genotypes. Based upon chi-square analyses for segregation in the F2 as well as upon the data from F1 and the backcrosses, it was proposed that protoplast culturability in these diploid potato plants is controlled by two independent loci with complete dominance.