Isolation And Identification Of Wheat Rhizosphere ACC Deanminase As Well As Assessment Of Their Inoculation Effects

Rhizosphere bacteria containing ACC deaminase can reduce stress ethylene level of crop under drought conditions, to improve drought resistance of crops. We isolated two kinds of rhizosphere bacteria which containing ACC deaminase, and identified with physiological and biochemical parameters in combination with molecular biological methods; then inoculated wheat with identified strains, we observed the inoculated effects on wheat growth and physiological metabolism. The results obtained are as follows:1. Using enrichment orientation method, we screen the PGPR use the medium which use ACC as a sole nitrogen source, subcultured several times, and finally those can use ACC as a sole nitrogen source can survive, and then diluted into solid ADF medium to separation the PGPR. Then we purify those have same colony color, shape, size and growth speed of the strains, the two strains which have ACC deaminase activity were isolated, we named strains AS and CS.2. According to the morphological observation, found that two strains are Garm-negative bacteria, the colony morphology is completely different; According to physiological and biochemical characteristics, found that there are many characteristics of the two strains are different, we can decide that two strains are not the same strain. Combination with 16S rDNA sequence analysis and sequence homology analysis, the 16S rDNA of AS and CS showed 98.25% and 99.60% homology with Enterobacter and Serratia, respectively. The accession number of AS and CS were AJ508302 and AJ233435.3. We use that enzyme unit divide the total protein concentration to meansure the activity of ACC deaminase of the strains, got the enzymatic compare energy of AS and CS was 0.0186 U/mg and 0.0167 U/mg, the two strains belongs to typical rhizosphere bacterium containing ACC deaminase activity. While we determined other growth-promoting mechanism such as producing siderophore, indole acetic and phosphate solubilization, found that the activity of indole acetic and phosphate solubilization of strain CS are stronger than strain AS, and the two strains have similar capacity of producing siderophore.4. Inoculate with strains AS and CS, we mensured ecological indicators, plant height, shoot fresh weight, root fresh weight and total fresh weight of wheat, found that these indicators were all increased under drought stress than the control condition, and shoot fresh weight was more obvious than root fresh weight, and increased 26.8% and 18.3%,separately.5. We measured physiological and biochemical indicators of wheat: the MDA content of wheat leaves inoculate with strains AS and CS under normal condition were reduced by 2.2% and 9.1% than control condition, the MDA content of wheat leaves inoculate with strains AS and CS under drought condition were reduced by 13.7% and 12.5% than control condition.Both in the roots, stems or leaves inoculate with strains AS and CS under drough condition, the soluble protein content were higher than control condition, particularly in the roots, the effect inoculate with strain CS was most significant.The antioxidant enzyme activity under normal treatments inoculated with strains was basically unchanged; The antioxidant enzyme activity under drought treatments inoculated with strains was increased than control condition, and the effect inoculated with strain CS was more obvious. And the effect inoculated with strains was more obvious in the roots, SOD activity increased by 48.2%, POD activity increased by 51.1% CAT activity increased by 99.6%; and the effects were almost the same in the stems and leaves, not obvious in the roots.