Isolation Of Plant Growth Promoting Rhizobacteria Of Rice And Their Influence On The Growth Of Rice

At present,Chinese agricultural production is mainly depending on chemical fertilizer and pesticide,but the excessive chemical fertilizer affects the crop quality, decreases the soil fertility pollutes environment,and has affected the sustainable development of agriculture greatly.Microbial fertilizer possesses many good features: high efficiency,low cost,energy-saving and non-pollution to the environment.The major roles of microbial fertilizers are to help plant uptake nutrient elements and produce various physiological active materials,which enhance plant tolerance to stress,improve qualities of farm products,and to reduce the application of chemical fertilizers.Therefore,the development of microbial fertilizer which can reduce the amout of chemical fertilizer could solve the problems of environmental pollution and eventually benefit the quality of produce and environment.Some strains of nitrogen-fixation bacteria,phosphate-solubilizing bacteria and potassium-solubilizing bacteria were isolated from rice rhizosphere by rice germ agglutinin(RGA) labeled with fluorescein isothiocyanate(FITC) as screening marker, and their morphology,physiology and biochemistry were studied.Rice germ lectin(RGL) was extraced from rice germ powder by PBS buffer solution,prcipitated with(NH₄)₂SO₄,purified through CM-Sepharose and lyophilized. The extraction rate of RGL was 0.165mg/g.The purified RGL was labeled with FITC by Marshall's method and the agglutinating titre was 125μg.ml^-1.The FITC-labeled RGL could be conserved for two years under-20℃condition.In the experiment 67strains of nitrogen-fixing bacteria strains were isolated from rice rhizosphere.13 stains were selected by RGL labeled with FITC.Total Kjeltec nitrogen was determined by Tecator Kjeltec auto-analyzer.Seven strains were selected among these 13 stains by their strong nitrogen-fixing ability.Strains 6107 and 6105 could significantly promote the growth of rice and increased the fresh weight of rice by 39%.The two stains were identified as Beijerinckia spp and Azotobacter spp, respectively.In the experiment 81strains of phosphorus-solubilizing bacteria strains were isolated from rice rhizosphere.Tweenty one strains were re-selected by RGL labeled with FITC.Inorganic phosphorus both in supernatant and inside cells were determined.Eight strains were selected among these 21 stains by their strong phosphorus-solubilizing ability.Strains 5310 and 5312 could significantly promote the growth of rice and increased rice fresh weight by 45%.These two strains were identified as Xanthomonas spp and Pseudomonas spp,respectively.In the experiment 19 strains of potassium -solubilizing bacteria strains were selected by RGL labeled with FITC.Inorganic potassium both in supernatant and inside cells were determined.Five strains were selected among these 19 stains by their strong potassium-solubilizing ability.Strains 7801 and 1106 could significantly promote the growth of rice.The two strains were identified as Pseudomonas spp and Bacillus spp,respectively.