Modelling the Ecophysiological and Genetic Control of the Staygreen Trait.

The staygreen trait has been recognised as a phenotypic indicator of drought adaptation in a number of species, but the underlying mechanisms are not well understood.  Various studies have implicated roles for canopy architecture, root system architecture, and transpiration efficiency and have pursued the physiological and genetic control of these processes.  We sought to capture the understanding from these studies in enhancing a dynamic crop model to simulate effects at crop scale of genetic variability in these processes using sorghum as a model crop. We explore the phenotypic consequences of this genetic variation in terminal stress environments, focusing in particular on the degree to which staygreen results as an emergent property of the system dynamics.  The likely value of each putative mechanism in target production environments in NE Australia was examined by simulation analysis.  The value of using quantitative and dynamic crop growth and development frameworks for better linking phenotype with genotype and thus improving drought adaptation via molecular breeding are discussed.