Construction of high density genetic map and QTL mapping in a sorghum Tx623A×sudangrass S722 population

Sorghum-sudanense is a hybrid of sorghum and Sudanese grass and is widely used in animal husbandry and aquaculture because of its high yield, excellent quality and wide adaptability. Its total fresh biomass yield, fresh biomass yield at each cut and nutritional quality are better than their parents. Using high-throughput sequencing, we constructed a high-density genetic map of sorghum Tx623A×sudangrass S722 with 103 recombinant inbred lines (RIL) in this study and mapped quantitative trait loci (QTLs) for plant height (PH), stem diameter (SD), tiller number (TN), fresh weight (FW) and dry weight per plant (DW). The map included 1,610 markers with a total length of 2,329 cM and QTL mapping identified 19 QTLs, including two for PH, three for SD, four for TN, four for FW and five for DW. We detected two QTL clusters containing overlapping QTLs for PH, FW and DW. Orthologs of three SD candidate genes from maize were found within two SD QTLs. The identification of these QTLs will be useful for dissecting important traits and developing marker-assisted selection (MAS) in future sorghum breeding programs.