Characterization of rhizobacterial strain Rs-2 with ACC deaminase activity and its performance in promoting cotton growth under salinity stress

A plant growth-promoting rhizobacterial strain Rs-2 with 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity was isolated from salinized soils using ACC as the sole nitrogen source. Based on its physiological and biochemical properties and 16S rDNA sequence analysis, this strain was identified as Raoultella planticola. The maximum value of nitrogen fixation, dissolved phosphorus and dissolved potassium of Rs-2 were 148.8 μg/ml, 205.0 and 4.31 mg/l, respectively within 192 h liquid culture. The germination rate of cotton seeds (Gossypium hirsutum L.) inoculated with Rs-2 (Rs-2-S) was enhanced by 29.5 % in pot experiments compared with that of the control (CK-S). Subsequently, individual plant height, fresh weight and dry weight of cotton seedlings in Rs-2-S treatment increased by 15.0, 33.7 and 33.3 %, respectively, compared with those in CK-S treatment. Statistical analysis showed that the inoculums of Rs-2 promoted significantly (P < 0.05) cotton growth. Further analysis showed that Rs-2 reduced the quantities of ethylene and abscisic acid in cotton seedlings, and increased indole acetic acid content in cotton seedlings under salinity stress. The accumulation of N, P, K+, Ca2+ and Fe2+ in the cotton plants was increased significantly (P < 0.05) in Rs-2-S treatment, whereas the uptake of Na+ in cotton seedlings decreased (P < 0.05). Hence, the present observations suggested that R. planticola Rs-2 could have a promising potential for promoting cotton growth and alleviating salinity stress.