Cultivar genetic gains from 50 years of irrigated sugarcane breeding in South Africa

Cultivar genetic gains provide a measure of benefits to growers from sugarcane breeding programmes and determine the effectiveness of cultivar development. The objective of this study was to determine the genetic gains for cane yield, percent estimated recoverable crystal (ERC%) cane and sugar yield of cultivars developed for the irrigated regions of South Africa after 50 years of sugarcane breeding. Data were derived from advanced cultivar trials planted in the early and mid-season in the Pongola and Mpumalanga regions. Significant (p < 0.01) cultivar differences were observed for cane and sugar yield and ERC% cane. There were significant (p < 0.05) season effects on ERC% cane and significant (p < 0.01) season by cultivar effects on ERC% cane and sugar yield, suggesting seasonal adaptation of cultivars. Cultivar genetic gains of 0.26 Mg ha−1 y−1 for cane yield, 0.03 Mg ha−1 y−1 for sugar yield and 0.06% y−1 for ERC% cane were observed. Genetic gains by sequence of release were 0.31 Mg ha−1 cultivar−1 for cane yield, 0.09 Mg ha−1 cultivar−1 for sugar yield and 0.06% cultivar−1 for ERC% cane. Cultivars released after 2000 produced genetic gains equivalent to 6% increase in sugar yield and 9% increase in ERC% cane compared with those released before 1990.