QTL analysis of salt tolerance in Sorghum bicolor during whole-plant growth stages

To study the salt tolerance genetics of sorghum, 181 recombinant inbred lines (RILs) were used to locate quantitative trait loci (QTLs) underlying salt stress adaptability. Six traits, namely, plant height (PH), stem diameter (SD), total biomass (TB), stem fresh weight (SFW), juice weight (JW) and Brix, were investigated under normal and salt stress conditions in two years. A total of 53 QTLs for the six traits under both conditions and their corresponding salt tolerance index (STI) were detected and phenotypic variation explained (PVE) ranged from 4.16% to 20.42%. Six of the QTLs, qTB6, qSFW9, qJW9, qBrix2, qBrix10 and qSTI-Brix9, were the main effect QTLs controlling salt tolerance and had a PVE more than 10%. qSFW9 and qJW9 colocalized in the same marker interval as SB5069-UGSM18 and had PVEs of 17.70% and 14.20%, respectively, with positive effects from L-Tian. QTL clusters controlling PH, TB, STI-TB, SFW and JW were consistently mapped in the marker interval of Xcup19-SB4177 on chromosome 7. These locations might serve as target sites for marker-assisted selection (MAS) in improving salt tolerance of sorghum.