A Simple Greenhouse Method for Screening Salt Tolerance in Soybean

Salinity is an important limiting factor for crop production. Over 800 million ha of land globally are salt-affected. Soybean [Glycine max (L.) Merr.] is moderately salt-tolerant; however, excessive salt reduces yield. Developing a quick, reliable, and inexpensive screening method is critical for soybean breeding programs. This study aimed to develop a rapid method for screening salt tolerance in soybean and to determine the best growing media and NaCl concentrations for screening. Four soybean cultivars, known as Cl-includers ('Williams' and 'Dare') or excluders ('S-100' and 'Lee 68'), were screened for salt tolerance. These four genotypes were grown in soil, sand, and potting mix and treated with 0, 80, 120, and 160 mM NaCl. Treatment was initiated at the first trifoliate leaf expansion in the second true node above the unifoliate leaves. Two weeks later, leaf scorch score on a 1-9 scale (1 = no chlorosis; 9 = necrosis) was taken. Additionaly, leaf and root Na+ and Cl- concentrations were analyzed. The clearest differences between tolerant and sensitive cultivars were obtained using 120-mM NaCl in soil. Once the best conditions to evaluate salt tolerance were established, 14 cultivars were screened to identify those with the most contrasting response. The most sensitive cultivars were Williams and 'Clark'; the most tolerant were 'HBK R5525' and 'AG5905'. To validate this method, 97 genotypes were evaluated under these conditions with differential responses. The proposed screening methodology was effective in identifying a range of sensitive and tolerant genotypes, allowing confirmation of salt tolerance in some previously reported genotypes.