Association Mapping of Salt Tolerance Using Worldwide Soybean Germplasm.

Salt stress causes foliar chlorosis and scorch, plant stunting, and eventually yield reduction in soybean. There are differential responses, namely tolerance (excluder) and intolerance (includer), among soybean germplasm. However, the genetic and physiological mechanisms for salt tolerance is not clear. A major quantitative trait locus (QTL) for salt tolerance in soybean has been mapped on Chromosome (Chr.) 3, which explains a large proportion of variation in response to salt stress. Identification of novel QTL for salt tolerance would help elucidate the salt tolerance mechanisms and also facilitate the development of salt tolerant cultivars through marker assisted selection (MAS). The objective of this study is to uncover genomic regions and SNP markers associated with salt tolerance by employing the single nucleotide polymorphism (SNP)-based genome-wide association mapping. A total of 292 lines from 31 countries were collected from germplasm resource information network (GRIN). These plant introduction lines along with checks (S-100 and Dare) were evaluated for salt stress response in greenhouse (25 ± 2 °C, 14 h photoperiod) of Rosen Center at University of Arkansas. Salt treatment using 120 mM NaCl solution was initiated at V1 stage (one set of unfolded trifoliolate leaves). Salt treatment was performed for 2hrs per day. Chlorophyll contents were measured around 12 days after the initiation of salt treatment. Chloride concentration were measured based on ICP-OES method. Genotypic data were obtained from SoySNP50K iSelect SNP beadchip assay. The genome wide association analysis was conducted using GAPIT. The salt tolerance QTL was confirmed on Chr.3. Four new QTL were identified on Chr. 13, 15, 17, and 18. QTL and linked SNP markers identified will be useful in MAS for salt tolerance.