Detection of reproducible QTL associated with bioenergy traits in sorghum across several growing environments

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 its genetic improvement. This study aimed to identify quantitative trait loci (QTL) associated with several bioenergy-related traits in sweet sorghum that include flowering time, plant height, total biomass, stem diameter, stem moisture percentage, and brix. We used 188 F-7 recombinant inbred lines (RILs) derived from a cross between a sweet sorghum (Wray) and a grain sorghum (Macia). The RILs and their parental lines were grown at two locations. Application of genotyping-by-sequencing analysis of the RILs allowed for constructing a map with 979 single nucleotide polymorphisms. Using the inclusive composite interval mapping of additive QTL, a major QTL for a flowering time was detected on chromosome 6, and explained 29.45% of the phenotypic variances (PVE). Major QTL for plant height (29.51% PVE) and total biomass yield (16.46% PVE) were detected on chromosome 7, and QTL for stem diameter (9.43% PVE) was detected on chromosome 1. Several QTL for brix were associated with sugar transporter genes, providing candidate genes for further study. For example, a major QTL for brix (39.92% PVE) was detected on chromosome 3 consistently across four environments. Twenty one QTL for five traits were detected across four environments using ICIM-ADD. The identified QTL in this study should aid in developing lines and hybrids of sorghum that are suitable for producing bioenergy.