The Genetic Basis of Grain Yield in Sorghum

Crop production must increase by 70% by 2050 in order to meet the expected requirements for population growth. While previous research has resulted in genetic improvement of the grain output in major cereal crops such as Zea mays and Oryza sativa, much less investment has been made to improve the grain yield of Sorghum bicolor, a drought tolerant grain and forage crop native to Africa. Multiple genetic and environmental factors influence grain yield making it challenging to identify the pathways determining the amount of grain produced. In this study, variation in grain yield, grain weight and grain number per plant were measured in a RIL population derived from BTx642, a drought tolerant line, and Tx7000, an R-line used for grain production prior to 1950 and subsequently in hybrid sorghum breeding programs. 14 QTL for grain yield, weight and number were identified. Several QTL were found to have alleles with opposing actions in increasing either grain weight or grain number which caused no QTL to be found at these positions for grain yield. Data from the BTx642xTx7000 population showed that selection for alleles at these loci that increase grain number has a greater probability of increasing grain yield than selecting the alleles for grain weight. In addition, QTL were identified that increased only grain number or grain weight leading to an overall increase in grain yield. This suggests that the traits modulated by these QTL are acting independently to increase grain yield of S. bicolor.