M Zhou
South African Sugarcane Research Institute, Durban, South Africa; Marvellous.Zhou@sugar.org.za
Genetic control references additive and non-additive genetic effects in plants and is used to determine breeding strategy. The objectives were to determine additive and non-additive genetic control for sucrose content and evaluate implications on sugarcane breeding. Data were collected from six irrigated and six rainfed South African unselected progeny populations planted in replicated family plots from 2015 to 2020 and measured from 2016 to 2021. Sucrose content was measured from the first 20 progenies in a family plot as Brix % using handheld refractometer. Data were analysed using best linear unbiased prediction (BLUP) of the linear mixed models in the Statistical Analysis System software to determine female, male (additive) and female x male interaction (non-additive) genetic variance. Ten of 12 populations produced significant (P < 0.05) additive variance compared to six of 12 that produced significant non-additive variance. Additive variance was larger than non-additive in nine of the 12 populations indicating higher additive genetic control than non-additive. Female parents produced higher additive variance than males, indicating maternal effects. All populations produced some parents with significantly (P < 0.05) higher additive BLUP values (breeding values), while only five of 12 population produced significant non-additive BLUP values (heterosis) indicating dominance of additive over non-additive genes. Proportion of total parents that produced significant breeding values was 6.6 % compared to 2.4 % female x male that produced significant heterosis. The results indicate that sucrose content is controlled by additive genes. Additive genetic control indicates that selecting parents with high breeding values will accelerate breeding for sucrose content. Higher maternal effects highlight the importance of selecting the female parents during hybridization while males must be complementary. Recurrent breeding and selection strategy can be implemented by crossing parents with high breeding values for sucrose and selecting for high values among progeny populations.