A Method for Screening Salt Tolerance in Soybean.

A method for Screening Salt Tolerance in Soybean Ledesma Fernando, Holifield Sharon F., Pengyin Chen, Richard A. Cartwright, Kenneth L. Korth and Tetsuaki Ishibashi   Salinity is an important problem for crop production. About 20% of irrigated agricultural land is affected by salinity in the world. Soybean [Glycine max (L.) Merr.] is a salt-sensitive species and excessive salt can reduce yield; nevertheless, there is genetic variation in response to salt stress.  Use of salt tolerant cultivars is an effective approach to minimizing yield loss where salinity is an issue.  In general, soybean genotypes have been screened for salt reaction in the greenhouse with labor-intensive, time-consuming, and costly hydroponic systems.  Development of a quick, reliable, and inexpensive screening method is critical for breeding program and genetics studies.  Four soybean cultivars (‘S-100’, ‘Lee 68’, ‘Dare’ and ‘Williams’) were evaluated for salt reactions in three growing media (sand, soil, and potting mix), under four levels of NaCl (0, 80, 120, and 160 mM), and at four growing stages (VE, VC, V1, and V2).  Leaf scorch score (LSS), plant height, root and shoot dry weight, and concentration of Na and Cl in plant tissue were measured.  S-100 and Lee 68 were tolerant while Dare and Williams were sensitive. Difference in LSS between tolerant and sensitive cultivars was 3.3, 4.2 and 2.4 on a 1-9 scale for 80, 120 and 160 mM NaCl, respectively.  Difference in LSS between tolerant and sensitive was 3.7 in sand as compared to 2.6 for potting mix.  Salt treatments at different growing stages were similar except for VC with shorter response time. Our results showed that salt screening was most effective when plants were grown in sand and subjective to 120 mM NaCl at VC stage.