Chapter 5 - Sorghum

Abstract

Sorghum is primarily grown in hot and dry regions worldwide in large-scale commercial operations and in smallholder farming settings. In these regions, sorghum shows comparative advantages over other summer cereals, including its capacity to fill grain during end-of-season drought. It is also broadly adapted to temperate, subtropical and tropical drylands, and irrigated environments. Worldwide, farmers face the challenge of growing sorghum in highly variable environments. Matching hybrid, agronomy, and environment enables farmers to design more profitable and less risky sorghum production systems. At the crop level, the growth of major organs is predicted based on their potential size, and then the capacity of the crop to capture resources (radiation, water, and nitrogen) to meet the demand is assessed. The extent of resource capture and biomass accumulation and the efficiency with which carbon and nitrogen are partitioned into grain will be discussed, with a focus on productivity under water scarcity. One of the challenges for future sorghum crop improvement will be the capacity to connect across scales from molecular to farm, utilising molecular understanding to develop combinations of plant-level traits that increase productivity at the field level. This will require cross-disciplinary integration to harness ‘big’ data from genotypic and phenotypic studies. Future research in sorghum will need to focus on adaptation mechanisms that manipulate water supply and demand scenarios such as canopy size and root architecture, respectively, and heat adaptation mechanisms. Considerable biological integration will be required to scale-up from the causal polymorphisms at genome level to the phenotype of interest in the field. A new crop modelling frontier is unfolding in plant breeding with the potential to add significant value to the revolution in plant breeding associated with genomic technologies.