Heterotic Grouping and the Heterotic Pattern among Chinese Rapeseed (Brassica napus L.) Accessions

Abstract

Heterotic groups and patterns are extremely important in hybrid breeding. Nine elite inbreds widely used in Chinese rapeseed hybrid breeding programs were crossed in a diallel mating design to develop 36 hybrids. These hybrids and their parents were evaluated for two successive years in northern China. Five different methods, which were based on specific combining ability (SCA) effects, SCA‐Yang's effects, molecular markers, heterotic group specific and general combining ability, and heterotic grouping based on the general combining ability of multiple traits, were compared for their ability to classify the tested inbreds into heterotic groups. With regard to grouping of inbreds, breeding efficiency, and cross‐mean yield variation explained by the cross types, the SCA method was the most promising, followed by the SCA‐Yang's and molecular marker methods. Using the SCA method, three testers (8D129, 8C343, and 8D153) and opposing heterotic groups [(8C108, 8C189, and 8D129), (8C343, 8C360, and 8E001), and (8C272, 8D153, and 8E019)] were identified across environments. Chinese southern and northern rapeseed lines formed a different heterotic group. Four outyielding crosses, 8D129 × 8E001 (high‐check heterosis, 29.52%), 8C343 × 8D129 (24.76%), 8C189 × 8C272 (23.98%), and 8C272 × 8C343 (22.95%), were identified as ideal hybrids for further extensive testing in multilocation trials and are promoted for adoption and commercialization in China.