Identification and inheritance of a partially dominant gene for yellow seed colour in Brassica napus

A yellow-seeded doubled haploid (DH) line no. 2127-17, derived from a resynthesized Brassica napus L., was crossed with two black-seeded Brassica cultivars 'Quantum' and 'Sprint' of spring type. The inheritance of seed colour was investigated in the F-2, and BC1 populations of the two crosses and also in the DH population derived from the F-1 of the cross 'Quantum' x no. 2127-17. Seed colour analysis was performed with the colorimeter CR-300 (Minolta, Japan) together with a visual classification system. The immediate F-1 seeds of the reciprocals in the two crosses had the same colour as the self-pollinated seeds of the respective black- and yellow-seeded female parents, indicating the maternal control of seed colour. The F-1 plants produced yellow-brown seeds that were darker in colour than the seeds of no. 2127-17, indicating the partial dominance of yellow seed over black. In the segregating BC1 progenies of the two crosses, the frequencies of the black- and yellow-seeded plants fit well with a 1 : 1 ratio. In the cross with 'Quantum', the frequencies of yellow-seeded and black-seeded plants fit with a 13 : 3 ratio in the F-2 progeny, and with a 3 : 1 ratio in the DH progeny. However, a 49 : 15 segregation ratio was observed for the yellow-seeded and black-seeded plants in the F-2 progeny of the cross with 'Sprint'. It was postulated from these results that seed colour was controlled by three pairs of genes. A dominant yellow-seeded gene (Y) was identified in no. 2127-17 that had epistatic effects on the two independent dominant black-seeded genes (B and C), thereby inhibiting the biosynthesis of seed coat pigments.