High-density genetic map construction and QTL mapping in the sorghum-sudangrass RIL population (M81×Sa)

Sorghum-sudangrass, a hybrid of sorghum and sudangrass has high productivity, strong adaptability, and superior quality and is widely used in animal husbandry and aquaculture. Parsing the genetic basis of major agronomic traits is very important for sorghum and sudangrass hybrid breeding. This study used a sweet sorghum M81 and sudangrass Sa hybrid to construct 174 F 11 populations. Single-nucleotide polymorphisms (SNPs) derived from genotyping using its Restriction-site Associated DNA Sequence (RAD-seq) of RILs to construct a high-density genetic map comprising 790 SNPs spanning 2101 cM, in which coverage of all ten chromosomes was greater than 80%. Inclusive Composite Interval Mapping (ICIM) was carried out to map Quantitative trait loci (QTL) for five forage traits. A total of 18 QTLs were identified for plant height (PH, 4 QTLs), fresh weight (FW, 8 QTLs), dry weight (DW, 3 QTLs), stem diameter (SD, 2 QTLs), and sugar content (SC, 1 QTL). In addition, two overlapping QTLs ( qFW9.2 / qDW9 and qFW10 / qDW10.2 ) were detected for FW and DW. Together, the RIL populations and high-density linkage maps in this study provide a theoretical basis for future sorghum-sudangrass hybrid forage breeding.