Trends in family and individual genotype variance components and broad-sense heritability among unselected South African sugarcane breeding populations

Abstract

Family evaluation has been adopted to improve selection in the early stages of sugarcane breeding. However, little knowledge is available for comparing families to genotypes among diverse sugarcane populations. The objectives were to determine and compare trends between family and individual genotype (genotype) variance components and broad-sense heritability (H) among unselected sugarcane progeny populations and evaluate the implications for sugarcane breeding. Data for stalk numbers, stalk height and stalk diameter used to calculate cane yield were measured from trials established in the Midlands, coastal and irrigated sites between 2010 and 2015. Family and individual genotype variance were significant (p < 0.001) for assessed traits indicating high family and genotype variability. Family variance was higher than genotype variance suggesting that family evaluation provided more insight into population genetic variability. Families had higher H estimates (21 to 96%) than genotypes (0 to 31%), indicating that selecting superior families would be more efficient than selecting genotypes. Family evaluation followed by efficient genotype selection within superior families is expected to increase genetic gains for cane yield. Populations with high family variance and H showed higher genetic variability and discriminating ability for cane yield among families.