| The rhizosphere microbes of plant are importance in agriculture, and beneficial to soil fertility maintaining, crops growth-promoting and pathogen inhibiting. They have potential for increasing growth and yield of non-legume crops like rice and corn. Microbial fertilizer possesses the advantages of low consumption of energy, high resource availability, improving quality of agricultural products and decreasing contaminant compared with chemical fertilizers, so the utilization of microbial fertilizer will has good effects on society and ecology.It is well known that plant growth-promoting rhizosphere bacteria which possess plant growth promoting (PGP) traits play important roles in plant growth processes. The results suggest that1. Out of49tested strains, P5313was not found to produced IAA, the production of IAA of34(69.39%) strains were in the range of1.19to9.60mg/L, the remaining14strains had higher production, the highest production was84.31mg/L (P5314).2.The siderophores production was measured by CAS assay,42(85.71%) strains produced siderophores, with22strains producing them at high amount5+. In order to distinguish the differences in siderophores production between the various strains with5+, this study determined the siderophores production of the22strains using broth dilution method,8strains were up to80+.3. In detection of phosphorus solubilization,46(93.88%) strains exhibited the ability to solubilize phosphate, arranging from1.52～161.70μg/ml.4. Most isolates showed nearly no ability by detecting the inhibition rate to five fungi pathogens of49strains. However, strain P5350showed satisfied ability to inhibit five tested fungi.5. Out of49tested strains,24(48.98%) strains possess ACC deaminase, the strains activity was in the range of0.0180to0.0866U/mg.Large tube cultivation method was used to determine the promoting effect of49strains on the growth in rice seedlings, semi-solid medium cultivated rice seedlings for15d, the results showed that the strain K7801, K7802, K7804, K7808, K2915, P1201, P5304and P5350possess significant growth-promoting effect on rice seedlings; these eight bacteria were inoculated into the roots of rice seedlings, they were cultivated by soil for30d, more significant promoting effect were obtained. By physiological and biochemical as well as16SrRNA identification, the results show that the strain K7802, K7804, K2915and P5304belong to Bacillus, strain K7801, K7808, P1201and P5350belong to Pseudomonas. The results indicated that the strains producing low concentration of IAA showed promoting effect on the primary root numbers, lateral root numbers and the stem dry weights of rice seedling, the strains with high concentrations of siderophore had significant promoting effect on the root dry of rice seedling, and the root dry weights were increased significantly with the high production of siderophore. But there was no significant correlation between the primary root numbers, lateral root numbers as well as the stem dry weights and siderophore production. Strains with high phosphorus solubilizing activities had significant growth promoting effects on the dry weights of both stem and root of rice seedling, but there was no significant correlation between the root length, plant height, primary root numbers as well as lateral root numbers and phosphorus solubilizing activities. The plant height, primary root numbers and root dry weight of rice seedlings were promoted when ACC deaminase at low activities, while the six indexes were promoted when ACC deaminase activities stronger.This experiment evaluate the growth-promoting physical activity of49rice rhizosphere bacteria, it revealed a growth-promoting mechanism of these strains initially, and provide reference for the study of specific biological fertilizer in rice. According to the results of semisolid experiments and pot experiments, eight excellent strains which had significant growth-promoting effects on rice seedling were selected. Pot experiment conditions and field soil environmental conditions are different, it requires further experiments to test and verify the colonization, growth and growth-promoting effect of these strains in the field soil. |
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