Plant design features that improve grain yield of cereals under drought

A sound understanding of the physiological basis of drought adaptation in cereals can assist crop improvement programs to target trait selection for variable stress environments, by incorporating such knowledge in dynamic crop growth simulation models. Based on detailed experiments on sorghum and maize, we identified physiological processes that explained observed differences in grain yield under drought stress for genotypes with similar transpiration efficiencies. If water availability restricts crop growth, grain yield can be increased by restricting pre-anthesis water use to maximize post-anthesis water availability. Sorghum can achieve this by restricting plant size through early anthesis or through reduced tillering in response to vigorous main shoot growth around the time of tiller formation. Early vigour is associated with high leaf area, due to either a high leaf appearance rate or increased leaf width. However, in genotype*management*environment situations with limited tillering, this adaptation mechanism has limited value. In the absence of tillers, maize can improve grain yield under drought by changes in dry matter partitioning that reduce competition for assimilates with the primary ear during the period when grain set is determined. We are incorporating these crop physiological determinants into the APSIM-Cereal crop growth model to simulate adaptation for a range of sorghum genotypes, grown across locations and years that encompass a range of drought stress patterns. Such analyses allow breeders to match selection criteria to prevalent drought patterns in their target population of environments and should improve the efficiency of crop improvement