Identification and Mapping of QTL for Bioenergy-Related Traits in Sweet Sorghum.

Sweet sorghum is a potential energy crop used for both biofuel and thermo-electrical energy because it accumulates high concentrations of carbohydrates and it produces high biomass. To be an efficient energy crop, sweet sorghum needs to be genetically improved. Marker-assisted breeding will be important in genetic improvement of sweet sorghum. The objective of the present study was to identify quantitative trait loci (QTLs) associated with bioenergy-related traits in sorghum. We used 188 F₇ recombinant inbred lines (RILs) derived from a cross between sweet sorghum (Wray) and grain sorghum (Macia). The RILs and their parental lines were grown at two locations in 2012 and 2013. Genotyping-by-sequencing (GBS) analysis of the RILs allowed the construction of a high-density genetic map with 912 single nucleotide polymorphisms (SNPs) for QTL analysis.  Using the inclusive composite interval mapping of additive QTLs, a total of 27 major QTLs for bioenergy-related traits in sorghum were identified, including anthesis date, plant height, biomass yield, stem diameter, brix, head moisture content, and grain yield. A major QTL for anthesis and head moisture content co-localized on chromosome 6, and explained 28.41% and 20.96% of the phenotypic variances (PVE), respectively. A major QTL for plant height (17.56% PVE) on chromosome 7 also co-localized with a major QTL for total biomass yield (20.96% PVE). A major QTL for brix (32.85% PVE), grain yield (29.88% PVE), and stem moisture content (15.78% PVE) co-localized on chromosome 3. A major QTL for stem diameter was detected on chromosome 6 (14.23% PVE). The identified QTLs in this study could help to further understand the underlying genes associated with bioenergy related traits and could be used for development of molecular markers for marker-assisted selection.