A Rapid and Effective Method for Screening Salt Tolerance in Soybean

Abstract

Salinity has been recognized as a constraint for soybean [Glycine max (L.) Merr.] production in many regions worldwide. Fortunately, genetic variation in salt tolerance is available in the soybean germplasm bank. However, current screening methodologies for salt‐tolerant genotypes are time‐consuming and often ineffective because of their limitations in detecting and measuring plant response to salinity. The objective of this study was to develop a rapid visual method for screening soybean genotypes in response to salt stress based on foliar symptoms. Soybean seedlings were grown in hydroponics with 0, 40, 80, 120, or 160 mM NaCl. Visual foliar symptoms of excessive NaCl were evident at 26 d after planting (14 d in 120 and 160 mM NaCl treatment). The NaCl level of 120 mM was most effective for salt‐tolerance screening based on visual foliar symptoms on a group of differential genotypes. Chloride includers (‘Williams’, ‘Clark’, ‘HBK R4924’, and ‘Dare’) exhibited interveinal chlorosis, while Cl excluders (‘S‐100’, ‘Lee 68’, and ‘HBK R5525’) showed no chlorosis at the 120 mM NaCl level. At this critical selection level (120 mM NaCl), average leaf Na and Cl− contents were 2.64 and 1.96 times higher, respectively, for Cl includers than for Cl excluders. Plant damage was more evident at 120 and 160 mM NaCl, as demonstrated by the decreased shoot and root biomass and near maximum accumulation of Na and Cl− in the tissue. There was a significant and negative correlation (r = −0.69, p = 0.0006) between relative root dry weight and Cl− concentration in the leaf. This methodology is simple, rapid, and effective for selection of Cl tolerant genotypes with a minimum investment of cost and time.