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Genotyping by sequencing for identification and mapping of QTLs for bioenergy-related traits in sweet sorghum
Sweet sorghum (Sorghum bicolor L. Moench) is a promising bioenergy crop. To increase the productivity of this crop, marker-assisted breeding will be important to advance genetic improvement of sweet sorghum. The objective of the present study was to identify quantitative trait loci (QTLs) associated with bioenergy-related traits in sweet 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 analysis of the RILs allowed the construction of a high-density genetic map with 979 single nucleotide polymorphisms. Using the inclusive composite interval mapping of additive QTLs, a total of 29 QTLs for bioenergy-related traits in sorghum were identified, including anthesis date, plant height, head moisture content, biomass yield, stem diameter, brix, grain yield, and 100 seed weight. Major QTLs for anthesis date and head moisture content were detected on chromosome 6, and explained 29.45% and 20.65% of the phenotypic variances (PVE), respectively. Major QTLs for plant height (29.51% PVE) and total biomass yield (16.46% PVE) were detected on chromosome 7, and QTLs for stem diameter (9.43% PVE) and 100 seed weight (22.97% PVE) were detected on chromosome 1. A major QTL for brix (39.92% PVE) and grain yield (49.14%) PVE co-localized on chromosome 3, was detected consistently across four environments, and is closely associated with a SWEET sugar transporter gene. Additionally, several other QTLs for brix identified in this study or reported previously were found to be associated with sugar transporter genes. The identified QTLs in this study will 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. ^ The C:N ratio might be an interesting trait for QTL analysis. The variation of C:N ratio among different genotypes of sorghum should be determined. In 2013, Macia, Wray, and four selected RILs with low and high stalk sugar content were determined for carbon and nitrogen partitioning and C:N ratio in stems, leaves, and heads. Carbon and nitrogen partitioning to plant parts was related to the biomass partitioning. Head was the largest portion of carbon and nitrogen in low stalk sugar content lines while stem was the largest portion of those in high stalk sugar content lines. C:N ratio of the stem, leaf, and head were not different between the six sorghum lines. ^
Teingtham, Kanokwan, "Genotyping by sequencing for identification and mapping of QTLs for bioenergy-related traits in sweet sorghum" (2016). ETD collection for University of Nebraska - Lincoln. AAI10155734.