Screening Of Functional Bacteria From Rhizosphere Soil Of Allium Plants In Inner Mongolia Grassland And Their Role In The Groeth Of Oats

The Inner Mongolia steppe is rich in plant resources.Wild Allium,as the associated species of grassland community,not only has important ecological functions,but also has ornamental,edible,feeding and medicinal values,as well as good stress resistance characteristics.Rhizosphere soil microorganisms are important part of ecosystem.Functional microorganisms are microbial communities with different functions,which can improve soil structure and fertility,affect nutrient absorption of host plants,and promote plant growth,physiological metabolism and disease resistance.In this study,the wild Allium plants in Inner Mongolia grassland community were selected as the research target,and their rhizosphere soil microorganisms were isolated and identified.The functional strains and high efficient strains with the ability of nitrogen-fixing,phosphorus solubilizing and potassium-dissolving bacteria were screened,and the growth-promoting effects on oat seedlings were analyzed.The main results are as follows:(1)The physical and chemical properties and enzyme activities of Allium rhizosphere soil were as follows:p H 5.97-8.16;nitrate nitrogen content 3.85-14.02mg/kg;ammonia nitrogen content 5.55-20.60 mg/kg;available potassium content30.66-91.05 mg/kg;available phosphorus content 20.06-39.22 mg/kg;urease content99.44-1605.25?g/d/g;sucrase content 25.31-139.48?g/d/g;catalase content27.40-68.45?mol/d/g.The range of FDA hydrolase was 5.19-54.17?mol/d/g.The range of alkaline phosphatase was 1.25-30.87?mol/d/g.The range of neutral phosphatase was 1.69-28.18?mol/d/g.The results showed that there were significant differences in physicochemical properties and enzyme activities among different rhizosphere soil samples(P<0.05).(2)599 strains of functional bacteria were screened preliminarily from 40rhizosphere soil samples of 7 wild Allium species.According to the morphology,39nitrogen-fixing bacteria,59 organic phosphorus solubilizing bacteria,58 inorganic phosphorus solubilizing bacteria and 22 potassium releasing bacteria were obtained.(3)The results of the re-screening were as follows:the nitrogen fixation capacity of 39 strains ranged from 3.22 to 12.26 mg/L,the strongest nitrogen fixation capacity of strain GN-17 was 12.26 mg/L,and that of strain GN-21 was only 3.22mg/L.The organic phosphorus-solubilizing capacity of the 59 strains ranged from4.62 to 75.45 mg/L.The strain R₁P-14 had the strongest phosphorus-solubilizing ability,while the strain R₁P-39 had the weakest.The inorangic solubilizing phosphorus ability of 58 strains ranged from 6.15 to 92.71 mg/L.The strain R₂P-34had the strongest solubilizing phosphorus ability,while the strain R₂P-33 had the weakest solubilizing phosphorus ability.The soluble potassium content of the 22strains ranged from 35.55 to 87.26 mg/L,among which strain JK-11 had the strongest dissolving potassium ability,with a potassium dissolving rate of 10.74%,while strain JK-5 had the weakest dissolving potassium ability,with a potassium-dissolving rate of only 0.39%.(4)11 species of the functional strains belonging to 1 genus were identified through morphological and molecular biological identification,including 8 strains of(Bacillus megaterium),6 strains of(B.aryabhattai),4 strains of(B.flexus),3 strains of(B.subtilis),4 strains of(B.cereus),4 strains of(B.circulan),and 3 strains of(B.qingshengii),3 strains of(B.Wiedmannii),3 strains of(B.thuringiensi),4 strains of(B.thermoproteolyticus),4 strains of(B.stratosphericus).(5)Four functional strains R₁P-18,R₂P-24,GN-17 and JK-11 were selected to inoculate Oat Seedlings,which had the strongest ability to degrade cellulose,nitrogen fixation and dissolving potassium respectively.The results showed that the biomass,chlorophyll content,starch content,soluble protein content,IAA content and root activity of oat seedlings were significantly increased by different inoculation methods(P<0.05),which indicated that the four functional bacteria had a growth promoting effect on Oat seedlings.In conclusion,there are abundant microbial resources in the rhizosphere soil of wild Allium plants in Inner Mongolia steppe,among which there are many excellent functional strains with growth promoting potential,which can promote the growth of plants to a certain extent.This study provides a theoretical basis for the development of efficient microbial agents and microbial fertilizers,and lays a research foundation for the utilization and protection of microbial resources in the rhizosphere soil of Inner Mongolia steppe plants.