Isolation Of Bacteria With Relieving-salt-stress And Growth-promoting Effect To Cotton And Preliminary Study On The Relevant Mechanism

Secondary salinization was largely occured after long-term introducing drip irrigation in the cotton field of Xinjiang. Aiming at advancing the seed germination rate and accelerating the cotton growth especially in the seedling stage, isolation the strains with relieving-salt-stress and growth-promoting effect to cotton in salt stress were carried out. 142 soil samples from plant rhizosphere of salinized land and salina were collected. 580 strains were isolated. Among of them, 263 strains were salt-tolerant. Through further tests, it was shown that 15 strains could increase the germinating rate and promote the growth of cotton radicle. The effect of Rs15-4 strain on the enhancing germinating rate and promoting cotton growth were best. The germinating rate of cotton treated with Rs15-4 strain was enhanced 11.8% compared with untreated control. The average root and stem length of cotton were increased of 27.8% and 17.0%, respectively. The average fresh weight and dry weight of cotton were increased of 14.92% and 7.2%, respectively. The energy index of cotton seeds were enhanced of 28.69% compared to the salt stress control. The germinating rate of cotton seed and growth of cotton seedling were promoted observably by Rs15-4å’ŒRs-5 in potted plant of salinized land and salina.According to the biological characteristics and physiological and biochemical properties, Rs15-4å’ŒRs-5 were identified as Arthrobacter and Azotobacter, respectively.Through test on the impacts of the relieving-salt-stress and growth-promoting bacteria to the saline tolerance of cotton in the germinantion process, it was showed that the cell membrane permeability in the cotyledon of the cotton treated by Rs15-4 strain was lower of 26.15% than that of the control. The soluble protein content was obviously higher of 29.30% than that of the control. The content of free proline enhanced 1.16 times compared to the control at the 7th day. The soluble sugar content was higher of 10% than that of the control from the 2nd day to the 6th day. The content of free praline in the cotyledon of cotton treated by Rs-5 strain was higher of 43.75% than that of the control at the 7th day. The soluble protein content was average higher of 52.57% than that of the control from the 2nd day. At the same time, the activities of the catalase (CAT), the peroxidase (POD) and the superoxide dismutase (SOD) and the content of malondialdehyde (MDA) were determined. The results showed that the activities of POD, CAT and SOD in the cotyledon of the cotton treated by Rs15-4 and Rs-5 were higher than the control although there had the fluctuation in the germinant process. The contents of MDA in the cotyledon of the cotton treated by Rs15-4 and Rs-5 were lower than the control. All these results demonstrated that Rs15-4 and Rs-5 could enhance the saline tolerance ability of cotton in the germinantion process.The impacts of the relieving-salt-stress and growth-promoting bacteria to the nutrients absorbability of the cotton root system were studied. It was showed that strains could...