Electrophoretic variation as a tool for determining seed purity and for breeding hybrid varieties of Brassica oleracea

Isozyme phenotypes at four known genetic loci were determined in parental inbreds and corresponding F₁ hybrid seed lots of four commercial broccoli, two cauliflower, and two cabbage varieties to determine seed purity. Most inbred lines were completely homozygous at all four loci but differed with respect to alleles at one to three loci. Several parental inbreds of the cabbage hybrids were segregating at two to three of the loci. Models were developed to estimate seed purity in cases where parents were either fixed or segregating at diagnostic loci. Estimates of contamination ranged from 1.5 to 40.1%. These estimates were comparable with those from commercial grow-outs with a tendency for the former estimates to be higher. It was concluded that more stable SI alleles or genetic male sterility should be used to reduce contamination. Electrophoretic variation was further discussed as a tool for selecting homozygous plants and for strong self-incompatibility.