Genetic control of high stearic acid content in the seed oil of the sunflower mutant CAS-3

A sunflower mutant, CAS-3, with about 25% stearic acid (C18:0) in the seed oil was recently isolated after a chemical-mutagen treatment of RDF-1-532 s eeds (8% C18:0). To study the inheritance of the high C18:0 content, CAS-3 was reciprocally crossed to RDF-1-532 and HA-89 (5% C18:0). Significant rec iprocal-cross differences were found in one of the two crosses, indicating possible maternal effects. In the CAS-3 and RDF-1-532 crosses, the segregat ion patterns of the F-1, BC1, and F-2 populations fitted a one-locus (desig nated Es1) model with two alleles (Es1, es1) and with partial dominance of low over high C18:0 content. Segregation patterns in the CAS-3 and HA-89 cr osses indicated the presence of a second independent locus (designated Es2) with two alleles (Es2, es2), also with partial dominance of low over high C18:0 content. From these results, the proposed genotypes (C18:0 content) o f each parent were as follows: CAS-3 (25.0% C18:0) =es1es1es2es2; RDF-1-532 (8.0% C18:0) =Es1Es1es2es2; and HA-89 (4.6% C18:0) =Es1Es1Es2Es2. The rela tionship between the proposed genotypes and their C18:0 content indicates t hat the Es1 locus has a greater effect on the C18:0 content than the Es2 lo cus. Apparently, the mutagenic treatment caused a mutation of Es1 to es1 in RDF-1-532.