Genotype-by-region interactions of released sugarcane varieties for cane yield in the South African sugar industry

Sugarcane (Saccharum spp.) yields in the South African sugar industry are affected largely by genotype by environment (G x E) interactions. The objectives of this study were to investigate the nature and magnitude of G x E interactions of selected sugarcane genotypes based on regional evaluation trials and to identify mega-environments to inform future testing strategies. The study was conducted across five regions in KwaZulu-Natal province. Ten sugarcane hybrids and one commercial check hybrid were evaluated using a randomized complete block design with four replications. Data collected were analyzed using the additive main effect and multiplicative interaction (AMMI 2) and genotype main effect plus genotype by environment interaction (GGE) bi-plot analyses. A combined analysis of variance detected significant variation for genotypes, locations, and crop year and their interactions for total cane yield, estimated recoverable crystal and sugar yield. Genotypes N19 and N40 showed broad adaptability for cane and sugar yields, whereas N51 and N12 were superior for sucrose percentage. High cane yields were achieved in the following environments: South Coast, North Coast, Hinterland and irrigated North regions. Overall, the Irrigated North region was the most suitable environment for discriminating among cultivars and for being a representative test environment. Two mega-environments (MGE) were identified for the industry; where Midland and Hinterland sites fell in the same MGE 1; and North Coast, South Coast, and Irrigated North were combined into MGE 2.