General and specific combining ability effects for sugarcane yield among South African breeding populations

Abstract

General combining ability (GCA) and specific combining ability (SCA) have been applied in breeding maize and other crops for decades. Sugarcane breeding has seen low genetic gains, which may be attributed to limited exploitation of GCA and SCA effects. The objectives of this study were to determine GCA and SCA effects for cane yield in unselected South African breeding populations, calculate the ratio of SCA to GCA effects, and evaluate the implications for sugarcane breeding. Data from 35 Stage 1 unselected populations was analysed to determine SCA and GCA variance. There was highly significant SCA variance compared to GCA variance across all populations suggesting that SCA effects were more important in sugarcane breeding than GCA effects. The SCA effects were larger than GCA effects suggesting that utilising SCA effects in sugarcane breeding will increase cane yield more than utilizing GCA effects. Between the GCA effects, female variance was greater and more significant than male variance, which was largely non-significant, suggesting potential confounding from the use of polycrosses at crossing where the true identity of the male parent is unknown. The SCA effects can be utilised in sugarcane breeding through the development of heterotic groups and reciprocal recurrent breeding and selection, a strategy routinely followed in maize breeding.