Physiological and Morphological Traits of Soybean Genotypes Inoculated with Bradyrhizobium japonicum Under Saline Soil Conditions

Soil salinity is a major abiotic stress that adversely affects plant growth, root development, water relations and photosynthetic performance. Beneficial rhizobia may contribute to improved plant growth and physiological functioning under saline conditions. Here, we evaluated the morphological and physiological responses of soybean (Glycine max L. Merr.) inoculated with Bradyrhizobium japonicum under saline soil conditions. Ten soybean genotypes, comprising five local breeding lines (BK-104, BK-85, Gen-2, Gen-15 and K4230) and five international varieties (Chukurova, Slavia, Fortuna, Kanada and Opus), were grown in saline soil collected from the Surkhandaryo Region of Uzbekistan. Seeds were inoculated with B. japonicum and cultivated in pots with five replicates. Forty-five days after sowing, root morphological traits and physiological characteristics were assessed. Root traits and physiological parameters, including photosynthetic pigments, water relations and gas exchange, were assessed. Significant genotype-dependent variation was observed across morphological and physiological traits (p < 0.05). Inoculated Chukurova showed a high root surface area (6.06 cm2) and root projected area (1.93 cm2), whereas Gen-2 exhibited the greatest total root length (51.64 cm). K4230 and Gen-2 showed comparatively high plant growth and biomass responses. Physiological traits also varied substantially among genotypes, indicating differential responses to saline conditions. These findings demonstrate phenotypic variation among soybean genotypes under salinity.