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The Identification of Genes Affecting Maturity and Biomass Yield in Sorghum bicolor
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Lignocellulosic biofuels are a promising source of renewable liquid fuel. Sorghum is a drought-resilient C4 grass that is grown for grain, forage, sugar, and biomass. It is a promising lignocellulosic biofuel feedstock because of its ability to accumulate large amounts of biomass with minimal inputs. Isolating and characterizing genes contributing to traits relevant to biomass yield is an important step in optimizing sorghum as a dedicated bioenergy crop. To that end, the three studies presented here use quantitative trait locus (QTL) mapping to explore the genetics of sorghum development as it relates to biomass accumulation. In the first study, six unique QTL are mapped across two environments for flowering time, stem length, and biomass characteristics in the expanded BTx623/IS3620C population with an improved genetic map. Two flowering time loci are identified that were not found in earlier studies of this population. Biomass QTL in this population colocalize with known flowering QTL and the Dwarf loci, highlighting the importance of lengthened vegetative growth and stem length to biomass accumulation. In the second study, a single gene encoding a NAC family transcription factor is isolated from a QTL for variation in stem aerenchyma formation. SbNAC_D expression is elevated in internodes soon after they reach full length where expression is correlated with aerenchyma formation. Expression of SbNAC_D is also correlated with the expression of the programmed cell death gene, SbXCP1. Lastly, the Maturity2 QTL from the population Hegari/80M is fine-mapped to a gene encoding a lysine methyl transferase. Analysis of the circadian expression of sorghum flowering time genes reveal that Ma2 contributes to delayed flowering by enhancing the expression of SbPPR37 and SbCO, which are co-repressors of flowering under long days.
Casto, Anna Lynn (2019). The Identification of Genes Affecting Maturity and Biomass Yield in Sorghum bicolor. Doctoral dissertation, Texas A & M University. Available electronically from