Evaluating salt tolerance in soybean core collection: germination response under salinity stress

High levels of soil salinity inhibit the growth of legumes such as soybeans, significantly reducing their productivity. This research aimed to assess the salt tolerance of soybean genotypes by evaluating seed germination at varying salt concentrations (100 mM, 150 mM, and 200 mM NaCl) from two seed source locations. A total of 198 soybean genotypes were analyzed post-germination using 10 quantitative traits: germination percentage, seedling fresh weight, seedling dry weight, seedling length, shoot length, root length, seedling vigor index-1, seedling vigor index-2, seedling water content, and salt tolerance. Analysis of variance (ANOVA) results indicated significant differences among treatments across both locations. Principal component analysis revealed that certain quantitative traits were more prominent at different salt concentrations, thus confirming varied responses to salt stress. Correlation analysis demonstrated a positive relationship between germination percentages and growth parameters such as fresh weight, dry weight, and vigor index. The study observed a decline in all quantitative traits as salt concentration increased, highlighting the stress experienced by plants during germination and growth under high salinity conditions. Using K-means clustering, the 198 genotypes were categorized into tolerant, moderately tolerant, moderately susceptible, and susceptible groups. This clustering helped identify genotypes exhibiting high tolerance (≥ 80% germination at 200 mM NaCl) and high susceptibility (≤ 40% germination at 100 mM NaCl) consistently across both seed source locations. Consequently, seven salt-tolerant genotypes (MACS 708, KALITUR, MACS 1037, IC 13050, MACS 1010, PK 1029, and MACS 173) and three salt-sensitive genotypes (HIMSO 1563, EC 391181, and EC 241920) were identified, providing new insights into soybean cultivation under saline conditions.