Assessment of salt tolerance and analysis of the salt tolerance gene Ncl in Indonesian soybean germplasm

Abstract Soybean [ Glycine max (L.) Merr.] is one of the most important legume crops in the world. However, soybean grain yield is extensively affected by environmental stresses such as soil salinity. In this study, we evaluated the germplasm of 51 Indonesian soybean accessions for salt tolerance to identify salt-tolerant germplasms for possible use in breeding for soybean salt tolerance. Based on experiments under hydroponic conditions, adding 100 mM of NaCl to a 1/2 concentration of Hoagland and Arnon solution, several Indonesian soybean germplasms, such as Java 7, Seputih Raman, Tambora, Ringgit (JP 30217), Sinyonya (early) and Sinyonya (late) were identified as salt-tolerant in terms of salt tolerance rate (STR) and leaf chlorophyll content (SPAD value) taken with the Konica Minolta SPAD-502 chlorophyll meter. The selected salt-tolerant germplasms were further evaluated under soil medium cultivation in pots irrigated with 100 mM NaCl for around 5 weeks. The six selected soybean germplasms again showed higher salt tolerance in terms of SPAD, STR and shoot dry weight. Expression analysis of the salt tolerance gene Ncl revealed a significant positive correlation between Ncl expression and salt tolerance, suggesting that Ncl is essential for salt tolerance in the Indonesian soybean germplasms we tested. The salt-tolerant Indonesian soybean germplasms identified in this study could be used in local soybean breeding practices for the improvement of salt tolerance.