No abstract

A dwarf early Brassica napus line (D-001), derived from crosses with Diplotaxis muralis, was crossed to two B. napus cultivars, 'Regent' and 'Pivot' to study the inheritance of earliness (days to bud, days to first flower, and days to maturity), height, and leaf number. Spaced plants of P1, P2, F1, F2, BC1, and BC2 generations for both crosses were grown in a completely randomized design at two locations in Manitoba in 1984. Results of means analyses indicated that additive gene action predominated for all traits for both crosses and both locations. In addition, dominance gene action was found to influence days to first flower, days to maturity, and leaf number for the D-001 × 'Regent' cross and all traits for the D-001 × 'Pivot' cross. Nonallelic interactions were nonsignificant in all cases. Genotype × environment interactions were not significant for all traits except height. Variance analyses indicated a predominance of additive gene action. Broad sense heritabilities for phenological traits ranged from 55 to 90%, while narrow sense heritabilities ranged from 0 to 81%. For height, broad and narrow sense heritability estimates were equal and ranged from 51 to 84%. Heritability for leaf number ranged from 73 to 82% for broad sense and from 49 to 77% for narrow sense estimates. The predominance of additive gene action and the high heritabilities associated with these traits suggest that D-001 may be useful as a source of earliness in B. napus breeding programs. Key words: Brassica napus, earliness, inheritance, Diplotaxis muralis.