Linkage Map Construction and QTL Mapping for Salt Tolerance in the Seedlings of Dongxiang Wild Rice (Oryza rufipogon Griff.)

Salt stress causes significant reductions in rice production worldwide; thus, improving salt tolerance is a promising approach to meet the increasing food demand. Wild rice germplasm is considered to be a valuable genetic resource for improving rice cultivars. However, information regarding the improvement of salt tolerance in cultivated rice using wild rice genes is limited. Given that Dongxiang wild rice (Oryza rufipogon Griff) is characterized by strong salt stress tolerance, in this study, to elucidate the molecular genetic mechanisms of salt-stress tolerance in Dongxiang wild rice, a backcross inbred line (BIL) population derived from an interspecific cross between Xieqingzao B (Oryzasativa L.) and an accession of Dongxiang wild rice was used for genetic linkage map construction and quantitative trait locus (QTL) mapping associated with salt tolerance at the seedling stage. The results showed that a linkage map consisting of 132 markers was constructed. Through evaluating the salt tolerance of 224 BILs at the seedling stage, a total of 11 QTLs related to salt tolerance were identified on chromosomes 2, 3, 4, 5, 7, 9, 11, and 12, with individual QTLs explaining 2.4-12.5% of phenotypic variance. All of the additive alleles in the QTLs were derived from O. rufipogon. In these QTLs, we found that 4 QTLs qDXWRST-1, qDXWRST-4, qDXWRST-9, and qDXWRST-10 did not overlap with QTLs previously reported for salt tolerance at the seedling stage of cultivated rice and could be considered as novel salt tolerance loci compared with cultivated rice. In addition, qDXWRST-1 and qDXWRST-9 were considered as new and unique loci for salt tolerance at seedling stage in Dongxiang wild rice. Overall, the favorable O. rufipogon-derived QTLs identified in the present study will provide new genetic resources for improving the resistance of cultivated rice against salinity stress using molecular breeding strategies in the future.