Utilizing Established Sorghum Mapping Populations to Identify QTL for Grain Yield and Compositional Traits

Sorghum [Sorghum bicolor (L.) Moench] is a cereal that produces grains rich in carbohydrates.  These carbohydrates are important for providing the necessary calories to both humans in Sub-Saharan Africa and Southern Asia, and livestock in the United States.  Grain yield and quality traits are key contributors to the amount of usable energy available for food and feed end-uses of cereal crops.  A total of 855 individuals with genotypic data from previously developed mapping populations, including a sorghum diversity panel (n = 380) and two recombinant inbred line populations (n = 280 and n = 195), were phenotyped in two years for grain yield per panicle, grain number and size, and grain compositional traits.  To better understand the genetic makeup underlying these traits, genome-wide association studies (GWAS) were implemented to identify genomic regions associated with individual grain yield components and macronutrients.  GWAS in the sorghum diversity panel alone provided strong marker-trait associations for these complex traits but many associations were not above the significance threshold in multiple years, likely contributed to limited statistical power and genotype x environment effects.  By conducting GWAS in multiple recombinant inbred line populations and finding common QTL, we were able to more confidently identify true associations and narrow down candidate genes for further study.  The loci identified from this study can also serve as markers for molecular breeding to help increase grain yield and improve grain quality, thus maximize grain sorghum’s caloric value per unit time, area, and production input.