Trends in Broad Sense Heritability and Implications for Sugarcane Breeding in South Africa

Relocation of South African Sugarcane Research Institute (SASRI) rain-fed research stations was due to urban encroachment and to increase representativeness of research farms. The relocation also coincided with the Recoverable Value (RV) payment system in 1998, which penalized growers for low sucrose content. After 12 years of trials, the large data set collected provided an opportunity to evaluate trends and progress. The objective of this study was to determine trends in broad sense heritability (H) over time and evaluate their implications on SASRI breeding strategies. Data were analysed using the mixed procedure of the Statistical Analysis System to estimate variance components used to calculate H. The coastal short cycle and midlands programs produced significant decrease in H for yield and marginal increase for sucrose content. The irrigated and coastal long cycle produced increase in H for yield. The breeding strategies resulting fromthe shift to RV payment system increased H for yield in irrigated and coastal long cycle probably due to stable populations for irrigated and increased efficiency for coastal long cycle. The coastal short cycle and midlands showed decreasing trends in H for yield probably due to intensive selection for sucrose content on populations with narrow genetic diversity. The H proved to be an effective parameter for evaluating breeding and selection strategies.