Genetic Analysis of Salt Tolerance in Soybean

Salt-affected soils significantly reduce land value and productivity. About 7% of the earth’s land and 20% of the irrigated land is affected by salt stress. Soybean [Glycine max (L.) Merr.] is generally regarded as a salt sensitive crop compared with other crops such as wheat, rice, and cotton. Genetic improvement of salt tolerance is essential for maintaining sustainable production in areas where soybean growth is threatened by salt stresses. To identify higher saline tolerance soybean germplasm, we evaluated more than 600 soybean accessions, including wild soybean [G. soja Sieb. & Zucc.], in a greenhouse condition, and several soybean genotypes, such as a Brazilian soybean cultivar FT-Abyara, a Chinese soybean cultivar Jindou 6, and a Japanese wild soybean accession JWS156-1, with high saline tolerance were identified. QTL analysis with four mapping populations derived from crosses between the tolerance lines and sensitive cultivars revealed a major saline tolerant QTL on soybean chromosome 3 flanking by SSR markers Sat_91, Satt255, Satt339, and Satt237. The QTL accounted for 31.3-68.7 % of the total variance for saline tolerance in the mapping populations. Using marker assistant selection (MAS), we developed near isogenic lines (NILs) for the saline tolerance QTL. Field test revealed the saline tolerance allele could greatly increase soybean grain yield in a salinity field condition. Map-based cloning approach was employed to isolate the gene coffering saline tolerance at this locus, and a candidate gene underlying the QTL was identified and characterized.