Fine-mapping QTLs and the validation of candidate genes for Aluminum tolerance using a high-density genetic map

Aims Aluminium (Al) stress is one of the most adverse abiotic factors limiting the growth and productivity of crops in acidic soils. Fine-mapping and cloning of quantitative trait loci (QTLs) provides an effective tool in analysing the genetic mechanisms underlying Al tolerance and in breeding Al-tolerant soybean varieties. Methods Soybean cultivar Huachun2 in South China has been reported to be highly tolerant to multiple abiotic stresses in acidic soils, including Al stress. Here, we employ a recombinant inbred line (RIL) population derived from a cross of Huachun2 and Wayao to investigate the Al-tolerance QTLs. The prioritization method and qRT-PCR were applied to predict candidate genes in each QTL. Additionally, the functions of GmGSTU9 and GmPrx145 were investigated in transgenic soybean hairy roots. Results In total, five QTLs associated with relative root elongation and Al content were identified by using the high-density genetic map in hydroponics. GmGSTU9, which encodes a glutathione S-transferase gene in qAl06, and GmPrx145, which encodes a class III peroxidase gene in qAl-HC2, were selected to further study the gene functions by using transgenic soybean hairy roots. In transgenic soybean hairy roots, the MDA, H2O2 and O-2(-) contents in GmGSTU9- and GmPrx145-overexpressing hairy roots were lower than those in the control and RNA-interference-exposed hairy roots under Al stress. Conclusions GmGSTU9 and GmPrx145 detected in qAl06 and qAl-HC2, respectively, positively regulate Al tolerance in soybean hairy roots by improving the antioxidant activity. These Al tolerance genes and molecular markers will be useful for marker-assisted selection to improve the Al tolerance of soybeans in acidic soils.