Sorghum is a C4 grass grown for grain, forage, sugar, and most recently biomass, though there has been very little genetic improvement for biomass yield. Most biomass sorghums are very late flowering to maximize vegetative growth. In order to understand the genetic control of flowering time and biomass yield in sorghum, we used a diverse panel of more than 400 exotic sorghum inbreds to perform association mapping for flowering time, biomass yield, and yield component traits. We also examined correlations between traits, correlations between inbred and hybrid performance, and the relationship between traits of interest and genetic diversity. Significant marker-trait associations were detected for maturity, plant height, and lodging. Forty percent of the variance in biomass yield is explained by plant height and lodging, inbred yield explained 82% of the variance in hybrid yield, and inbreds from all genetic subpopulations were represented in the top 5% of yield entries over two years. To better understand the reported epistatic interaction between two major flowering time loci, Ma5 and Ma6, we also performed linkage mapping in two biparental populations (Tx623 x Tx2909 and Tx623 x Tx2910) thought to be segregating for functional variation at both Ma5 and Ma6. Linkage mapping results suggest that the architecture of the photoperiod-sensitivity response differs between these two populations. Overall, our results suggest there is abundant genetic variation to quickly improve sorghum biomass yields by incorporating novel alleles from exotic sorghum.
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Genetic control of flowering time and biomass yield in sorghum
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