Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/20/2004
Publication Date: 11/15/2004
Citation: Lee, G.J., Carter Jr, T.E., Villagarcia, M.R., Zhou, X., Li, Z., Gibbs, M.O., Boerma, H.R. 2004. A major qtl conditioning salt tolerance in s-100 soybean. Theoretical and Applied Genetics, 109:1610-1619. Interpretive Summary: Salt damage limits soybean yield in certain areas of the USA- Arkansas in rice rotations, North Carolina in coastal areas subject to ocean flooding during hurricanes, and drier areas of the upper Midwest (e.g. Nebraska and Minnesota). Genes for resistance to salt damage exist in soybean. A major gene for resistance was detected in the old Southern variety Lee. However, very little breeding progress has been made in this area, because no economically viable screening method has been developed that breeders can use. To remedy this problem, we developed a salt resistance screening method. The new greenhouse method correlated well with actual field results in high-salt fields. We also identified the actual location of the resistance gene in the soybean genome using molecular (QTL mapping) work. These efforts are a significant step forward in salt tolerance breeding, and should facilitate commercial breeding for salt resistance in soybean.
Technical Abstract: Deployment of salt tolerant cultivars is an effective approach to minimize yield loss in a saline soil. In soybean, substantial genetic variation exists for salt response. However, breeding for salt tolerance is hampered because no economically viable screening method has been developed for practical breeding. To facilitate development of an effective screening method for salt tolerance in soybean, the present study was conducted to determine the heritability of salt tolerance and to identify associated quantitative trait loci (QTL). F2:5 lines from the cross of 'S-100' (salt tolerant) x 'Tokyo' (salt sensitive) were evaluated in a saline field in Hyde County, NC in 1999 and in a greenhouse located in Raleigh, NC in 2001. S-100 and Tokyo are ancestors of popular soybean cultivars released for the southern USA. The genotypic correlation between field and greenhouse ratings was 0.55, indicating reasonably good agreement between the two screening environments. To identify QTL associated with salt tolerance, each line was characterized with RFLP and SSR markers, and an initial QTL single-factor analysis was completed. A major QTL for salt tolerance was discovered on Linkage Group (LG)-N, accounting for 41%, 60%, and 79% of the total genetic variation for salt tolerance in the field, greenhouse, and combined environments, respectively. The QTL allele associated with tolerance was derived from S-100. Pedigree tracking was used to examine the association between the salt tolerance QTL and flanking SSR marker alleles in U.S. cultivars descended from S-100 or Tokyo through 60 years of breeding. The presence of flanking SSR alleles from S-100 was always associated with salt tolerance in descendents. The strong relationship between the SSR marker alleles and salt tolerance suggests that these markers could be used for marker-assisted selection in commercial breeding.