University of Arkansas, Fayetteville Division of Agriculture
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Abstract

Chlorine (Cl) toxicity has been recognized as a constraint for soybean production. Although the use of a Cl-tolerant crop easily solves the problem, current screening methodologies for Cl tolerance are often ineffective because of inadequate means of detecting and measuring plant response to salinity. In order to facilitate the evaluation process and selection of Cl-tolerant genotypes, a study was conducted to develop a rapid and effective method for screening Cl tolerance in soybean. Seeds of five soybean cultivars, each representing either the includer or excluder genotype to salt stress, were grown in a greenhouse in two different growing media (potting mix or sandy loam) with four different concentrations of sodium chloride (NaCl) solutions. Visual symptoms of Cl toxicity were rated on a 1 to 6 scale (1 as healthy and 6 as dead), and the score was compared with relative shoot/ root dry weight and Cl concentration in shoot/root to corroborate the accuracy of the visual ratings. Reduced dry weight was associated with higher Cl concentrations in both root and shoot tissues. The optimal NaCl concentration for screening was determined as 120 mM NaCl since it effectively differentiated excluders from includers. There were negative, significant correlations between relative shoot dry weight and Cl concentration in shoot tissue (r = -0.91 p = 0.05), and Cl concentration in shoot was also significantly correlated with visual rating score (r = 0.79 p = 0.05). The presented methodology is simple, rapid, and effective for screening for salt tolerance in soybean.

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