Sugarcane for water-limited environments. Genetic variation in cane yield and sugar content in response to water stress.

Water limitation is a major production constraint for sugarcane worldwide. However, to date, there has been little investigation of patterns of genetic variation in the response to water stress in sugarcane. Field experiments were conducted over 3 years under fully irrigated and managed water stress conditions at two locations in Northern Queensland in Australia. Eighty-nine genetically diverse clones were evaluated for their yield performance and sugar attributes. Water stress treatments reduced cane yield [tonnes of cane per hectare (TCH)] and total dry matter (TDM) by 17-52% and 20-56%, respectively, compared with irrigated treatments in the same experiments. Nevertheless, there was little genotype×environment interaction variation for TCH, TDM, or commercial cane sugar (CCS), and hence high genetic correlations between the irrigated and water stress treatments across environments. Both commercial and unselected clones performed poorly under severe stress environments, while the commercial clones outperformed the unselected clones under mild and moderate stress conditions. The results presented here highlight the contribution of intrinsic potential yields (yield under well-irrigated conditions) of some selected and unselected clones to maintain relatively high productivity in a range of moderate stress conditions imposed. The physiological basis for the high genetic correlations is at present unclear, but some explanations are hypothesized. The choice of stress levels in selection trials would not appear to be a critical issue for sugarcane breeding programmes, at least for the early phases of selection, where similar ranking clones across a range of moderate water stresses may be expected.