GENETIC VARIATION IN TRANSPIRATION EFFICIENCY IN SUGARCANE AND ITS POTENTIAL IMPACT ON YIELD IN RAINFED OR LOW IRRIGATION ENVIRONMENTS

IN WATER LIMITED environments, biomass growth can be considered as the product of biomass produced per water transpired, which is termed transpiration efficiency (TE), and water transpired. In work reported in this paper we screened 100 clones representative of those available in the Australian sugarcane breeding program for transpiration efficiency. This used pot experiments where water was carefully monitored and measured and biomass production recorded. TE was found to have a range of approximately ±20% of the mean. The variation found in commercially elite parents and cultivars was approximately as large as that observed among related wild germplasm. The potential impact of this variation in rainfed commercial production environments was examined by using the crop growth simulation model APSIM and varying the TE coefficient assumed to describe the genetic characteristics of cane being simulated. Growth and yield were simulated across 11 locations using historical weather data and assuming limited irrigation. The results suggest that for each % unit change in TE in most rainfed environments where there was no irrigation, on average a corresponding 0.5% to 0.9% change in biomass yield arises, although responses were lower (0.3–0.4%) as expected in the highest rainfall location. Supplemental irrigation was associated with slightly smaller responses. These results may be used in future to assign appropriate weightings to TE in selection indices in sugarcane breeding programs.