| Interaction effect of six phosphate solubilizing bacteria (Jm170, Jm92, Lx191, Lx22, Jx59, and Lx81) and four nitrogen-fixing bacteria (W5, N4, G, S11) were studied by using Molybdenum blue, Salkowski colorimetry and Plate duel culture. Characteristics of responsing to environmental factors, solubilizing phosphorus, secreting indole acetic acid (IAA) and antagonizing plant pathogenic fungi were tested. The effects of the growth of alfalfa (Medicago sativa L.) under the treatments of single strain and mixed strains inoculum were tested based on pot culture as well. The results showed as follow:1. There was no antagonism among six phosphate solubilizing strains and four nitrogen-fixing bacteria strains, so they can be cultured mixed. Compare with single strain, mixed strains of phosphate solubilizing bacteria and nitrogen-fixing bacteria had a wider range of adaptation, for instance, the culture temperature, the pH, the salinity.2. The phosphorus-solubilizing ability of most mixed bacteria strains was significantly increased compared with single strain. The phosphate-solubilization capacity of the treatments of Jx59+G, Lx22+G and Jm92+G were 306.26 mg/L, 291.43 mg/L and 235.22 mg/L, which were higher than the sum of the two strains cultured alone by enhancing 42.28%, 46.91% and 52.02% respectively. The phosphorus-solubilizing ability of a small number of mixed bacteria strains significantly decreased compared with single strain. The phosphorus-solubilizing capacity of the treatments of Lx191+W5, Jx59+N4 and Jm92+S11 were lower than bacteria strains cultured alone by reducing 44.88%, 32.52% and 16.28% respectively.3. The phosphorus-solubilizing ability of treatment of Jm92+Lx22+G was the highest in the mixed strains of phosphate-solubilizing bacteria and nitrogen-fixing bacteria, which was 330.42 mg/L, by enhaning 40.47% and 13.38% compared with the treatments of Jm92+G and Lx22+G respectively. The phosphorus-solubilizing ability of the treatment of Jm92+Lx22++S11+G was also high, which was 322.55 mg/L, by decreasing 2.43% compared with the treatments of Jm92+Lx22+G.4. The organic acids content of most mixed bacteria strains was significantly increased compared with the single strain. The phosphorus-solubilizing capacity was related to the pH and the organic acids content prominently, when phosphate solubilizing bacteria cultured alone. But the phosphorus-solubilizing capacity was hardly related to the pH and the organic acids content, when phosphate solubilizing bacteria and nitrogen-fixing bacteria cultured mixed.5. Strain G had the most active ability to produce IAA, which up to 37.34μg /ml, when phosphate solubilizing bacteria and nitrogen-fixing bacteria cultured alone. Treatments of Lx22+G and Jm92+N4 had a stronger ability to produce IAA than other treatments, which was up to 36.71μg /ml and 33.19μg /ml when phosphate solubilizing bacteria and nitrogen-fixing bacteria cultured mixed. The ability to produce IAA of treatments of Jm92+N4, Lx191+N4 and Jm92+N4 were higher than the sum of the two strains cultured alone by enhancing 428.81%, 162.5% and 7.89% respectively. Among all the treatments, Lx191+Lx22+G had the strongest ability to produce IAA, which was 41.15μg/ml.6. Among the 48 treatments of phosphate solubilizing bacteria and nitrogen-fixing bacteria cultured mixed, only 9 treatments possessed the positive antagonism, which antagonized against Rhizoctonia solani (pepper strain), Fusarium oxysporum f. Niveum and Rhizoctonia solani (cotton strain). Inhibition ratio of treatment of Jm92+N4, which antagonize against three plant pathogenic fungi, was the highest, 80.38%, 79.06% and 75.12% respectively.7. The phosphorus-solubilizing ability of phosphate solubilizing bacteria preserved by the method of Vacuum Freeze-drying Preservation was stronger than the method of Periodic Transplantation Preservation and Distilled Water Preservation. It was a better choice to preserve phosphate solubilizing bacteria for the long time by the Freeze-drying Preservation.8. Single and compound inoculum treatments had an obvious effect on the height, the root length, the nodule number, the above-ground biomass and the underground biomass of alfalfa, compared with control. Compound inoculum treatment had a better effect than single inoculum treatment on the quality of alfalfa growth. The treatment of Jm92+Lx22+S11+G had more benefit than other treatments, and the above-ground biomass increased 121.21% compared with control. Treatments of Jm92+Lx22+G and Jm92+Lx22+N4+S11 also had a better effect so that the above-ground biomass increased 69.24% and 60.15% respectively compared with control. 9. Mixed bacteria strains were better than single bacteria strain on the absorption of phosphorus and nitrogen on alfalfa, among which the treatment of Jm92+Lx22+G had the best effect. Nitrogen and phosphorus content of alfalfa increased than control, among which the treatments of Jm92+Lx22+G and Jm92+Lx22+N4+S11 had better effect also. These three mixed strains were expected to become the new rhizosphere inoculant or the biofertilizer of alfalfa. |
PDF Full Text Request