Michael Stamm

Heterosis and combining ability analysis in Chinese semi-winter × exotic accessions of rapeseed (Brassica napus L.)

Fourteen accessions (spring and winter types) and four testers (semi-winter type) of rapeseed (Brassica napus L.) were crossed in line × tester mating design to estimate general and specific combining ability for seed yield, yield components, and oil content. The F1 hybrids and their parents were evaluated in four environments in northern China. Highly significant differences were detected among the parents and hybrids for all the traits across environments. Plant height, setting position of first primary branch and length of terminal raceme were controlled by additive genes, whereas primary branches per plant, siliques on terminal raceme, siliques per plant, seeds per silique, seed yield per plant, 1000-seed weight, oil content, and seed yield were controlled by non-additive gene action. The accessions SP-Armada, 9E49, and CZ25 and the tester Zhong9 were good general combiners for seed yield. Among the 56 F1 hybrids, four hybrids: Zhong9 × CZ25, GZ1R × 9E38, Zhong7 × 9E38, and Zhong7 × CZ49 showed higher yield than the control and were the outstanding combinations for seed yield. These hybrids were recommended to be included in future breeding programs for development of new high yielding varieties with more desirable traits. Both winter and spring germplasm have potential in Chinese semi-winter rapeseed breeding program, for seed oil content improvement, more attention may be paid to spring germplasm.