Quantitative trait locus mapping for salt and drought tolerance traits in wheat (Triticum aestivum L.)

Wheat (Triticum aestivum L.) is susceptible to abiotic factors during its growth period, such as salt and drought. The germination stage is the initial growth stage of wheat growth, when wheat is particularly sensitive to salt and drought stress.

In this study, the genetic basis of salt and drought tolerance in wheat was explored using a recombinant inbred lines (RILs) population consisting of 188 lines derived from a cross between the cultivars Kenong9204 (KN9204) and Jing411 (J411). The KJ-RIL lines and their parents were evaluated under 100 mM NaCl salt stress and 10% polyethylene glycol 6000 (PEG-6000) induced drought stress. A principal component analysis (PCA) showed that the cumulative contribution rate of the four principal components was 87.16% and 85.62% under salt and drought stress, respectively. A total of 16 salt-tolerant and five drought-tolerant lines were selected using the membership function and 52 putative additive quantitative trait loci (QTLs) and 251 epistatic QTLs (eQTLs) for eight traits were detected in the KJ-RILs. Among the 251 eQTLs, 19, 32, 67, 21, 27, 29, 32, and 24 pairwise eQTLs were observed for sheath length, seedling length, maximum root length, root number, seedling fresh weight, root fresh weight, seedling dry weight, and root dry weight, respectively. The 52 putative additive QTLs were found in all of the 21 wheat chromosomes except 1A, 2D, and 4A. The QTLs accounted for 3.92-13.26% of the phenotypic variation with logarithm of the odds values ranging from 2.52-6.91. A total of seven stable QTLs were detected: qShl-1D, qShl-3B, qSl-4D, qMrl-1D, qRn-2A.3, qRn-4B, and qRdw-7D, and three major QTLs were detected: qShl-4B, qRn-3B, and qRfw-7D. Among them, qShl-3B was a stable major QTL that explained 10.96%-12.02% of the variation rate and the most favorable allele came from KN9204. In addition, an InDel marker closely linked to qShl-3B was developed and validated in 188 RILs.

Different putative additive QTLs and epistatic QTLs (eQTLs) located on most of the 21 wheat chromosomes were detected for the studied traits. Of which, a total of seven stable QTLs and three major QTLs were detected. In addition, an InDel marker closely linked to the stable major QTL, qShl-3B was developed and validated in 188 RILs, providing important information for the genetic improvement and development of salt and drought tolerance wheat varieties.