Quantitative Trait Loci for Chloride Tolerance in ‘Osage’ Soybean

Salt is a severe abiotic stress that reduces soybean [Glycine max (L.) Merr.] yield by > 20% in saline soils and irrigated fields. Marker-assisted selection (MAS) is an efficient method to identify salt-tolerant soybean lines. 'Osage' is a salt-tolerant and high-yielding cultivar in the Mid-South of the United States and is a distant progeny tracing five generations back to 'S-100'. The objective of this study was to determine the inheritance of salt tolerance in Osage soybean by identifying the quantitative trait loci (QTL) controlling the trait. A chloride (Cl-) includer, 'RA-452', was crossed with Cl-excluder, Osage, to develop an F-4:6 mapping population. The F-4:6 lines were genotyped by 5403 single nucleotide polymorphism (SNP) markers spanning 20 chromosomes (Chr.), of which, 1269 were polymorphic. The salt stress response of F-4:6 lines, along with parental genotypes, was evaluated in the greenhouse in April and June 2013. Three different treatments (120 mM NaCl, 120 mM KCl, and water) were initiated at V1 stage and continued for similar to 18 to 21 d. The leaf Cl-contents were quantified by inductively coupled plasma optical emission spectroscopy. Composite interval mapping analysis indicated that a major Cl--tolerant QTL was confirmed and narrowed down on Chr. 3 in both NaCl and KCl treatments, a novel Cl--tolerant QTL on Chr. 15 was identified in NaCl treatment, and a novel Cl--tolerant QTL on Chr. 13 was identified in the KCl treatment. Two annotated genes, Glyma. 13G161800 and Glyma. 15G091600, were proposed to be the candidate gene conferring the Cl-tolerance within QTL region on Chr. 13 and 15, respectively. A total of 27 SNP markers were significantly associated with Cl-tolerance, which could be used for MAS in breeding salt-tolerant soybean lines.