Heterosis and combining ability estimates in spring-planted oilseed rape (Brassica napus L.)

Abstract

A 6 × 6 diallel cross was conducted in spring-planted oilseed rape (Brassica napus L.) in 1983 at Elora and Dundalk, Ontario. The F1 hybrids exhibited positive heterosis for seed yield, of up to 72%, over the higher-yielding parent in the hybrid crosses. Heterosis for 1000 seed weight, percent oil, plant height, and lodging resistance was nonsignificant; negative heterosis for percent protein was observed with some hybrids. Generally, the hybrids were intermediate to the parents in flowering date and physiological maturity. Specific combining ability was more important than general combining ability for seed yield, percent oil, percent protein, plant height (Dundalk), and lodging resistance (Elora); specific combining ability was as important as general combining ability for 1000 seed weight, physiological maturity, plant height (Elora), and lodging resistance (Dundalk). The cultivars 'Topas' and 'Regent' were the best general combiners for seed yield. The best specific combinations for seed yield heterosis, 'Westar' × 'Hanna', 'Regent' × 'Liné', and 'Regent' × 'D-1', exhibited average high-parent heterosis values of 50, 38, and 30%, respectively. The results demonstrated that considerable potential exists for producing high-yielding single-cross hybrids of oilseed rape. Commercial exploitation of this heterosis will depend on the successful development of suitable pollination control mechanisms.Key words: Brassica napus, oilseed rape, F1 hybrid, heterosis, combining ability.