GENOTYPE BY ENVIRONMENT INTERACTIONS ACROSS THE AUSTRALIAN SUGARCANE INDUSTRY

TWENTY-FOUR trials were planted over the sugarcane regions of Australia (Northern NSW, Southern, Central and Northern Queensland, the Burdekin, Herbert and Ord river districts) and harvested in 2000 to 2002 in plant and first ratoon crops. Each trial comprised about 42 genotypes, randomly selected from several crosses, together with 5–6 commercial cultivars. The objective was to evaluate unselected genotypes, i.e. genotypes representative of those routinely evaluated in the early stages of selection in sugarcane breeding programs, and to consider the results in relation to optimising the coordination of data usage and germplasm exchange between the regional sugarcane breeding programs. This paper provides an initial examination of the results from this research. Pooled analysis of variance revealed that Genotype x Environment (GxE) interactions were important, with the relative variance component ratio of genotype main effect to GxE being 1.77 for CCS and 1.25 for cane yield (TCH). Genotype x Site interaction effects were greater than Genotype x Crop-years interaction effects within and across regions, especially for TCH. The 3-way (Genotype x Site x Crop-year) interaction effect was often substantial within and across regions, especially for CCS. A large proportion of GxE interaction variance was retained within regions, and average performance of genotypes within regions correlated well with average performance across all regions. This suggests important factors driving genotype x site interactions are sampled within any individual regions rather than being region specific. Averaged over regions, there were relatively strong phenotypic correlations for CCS and TCH between regions (> 0.5) in most cases. Some regions (e.g. North and Herbert) were relatively well correlated for both CCS and TCH and could potentially benefit from more coordinated evaluation and usage of germplasm in early stage selection trials in the future.