Genetic Regulation of Grain Weight and Size in Sorghum: Emerging Insights and Future Opportunities for Yield Enhancement

ABSTRACT

Grain weight and size are among the most important yield traits in sorghum. They exhibit positive and negative correlations with several other agronomic traits. They are highly heritable and therefore have significant scope for genetic improvement. However, these are complex traits and are difficult to dissect, and much of their current mechanistic understanding derives from rice and maize rather than from direct evidence in sorghum. Here, we review the current knowledge of genetic regulation of grain weight and size. We discuss the relative contribution of genetic factors to the determination of potential grain weight in sorghum. We provide a comprehensive update on molecular networks, genetic loci, causal genes, and candidate genes identified to date for the regulation of sorghum grain weight and size. We also describe the various floral, fertilization, and seed‐related factors that determine grain weight. Further, we discuss the roles of the rate and duration of grain filling in the determination of sorghum grain weight and size. Furthermore, we outline potential strategies for engineering sorghum varieties with improved grain weight and size without compromising the grain number. These strategies include precision breeding, analysis of allelic variation, and identification of desirable alleles from wild germplasm. We also discuss the applications of omics resources and genome editing in developing improved sorghum cultivars.