Study On Microbial Diversity Growth Promoting Bacteria With ACC Deaminase Activity In Rhizosphere Of Paeonia Lactiflora Pall.

The massive use of chemical fertilizers and pesticides has a great impact on the soil and the environment.As a kind of beneficial microorganism,plant growth promoting rhizobacteria(PGPR)can not only promote plant growth,but also replace chemical fertilizers and pesticides to improve the environmental pollution caused by excessive application of chemical fertilizers and pesticides.Therefore,the exploration and utilization of efficient PGPR resources is of great significance to the development of modern agriculture and the restoration and governance of the environment.Paeonia lactiflora Pall.belongs to the genus Paeonia L.in the family Paeoniaceae,which is a kind of perennial herbaceous plants.In addition to being the traditional flower of China,it also has high medicinal value.However,there are relatively few studies on the exploitation of PGPR resources and the growth promotion potential of P.lactiflora.In view of this,in this study,the rhizosphere soil of P.lactiflora was used as the research object.On the one hand,the diversity of the rhizosphere microbial community and its relationship with environmental factors were analyzed by high-throughput sequencing technology;On the other hand,using ACC as the only nitrogen source,the PGPR that can produce ACC deaminase activity was screened using a targeted enrichment method,combined with colony morphology,physiological biochemistry and molecular biology.On this basis,through the screening of PGPR with strong ACC deaminase activity was returned to the rhizosphere of P.lactiflora to verify its growth-promoting characteristics and growth-promoting effects,in order to provide basic information for the development and utilization of P.lactiflora rhizosphere growth-promoting bacteria.The main findings are as follows:(1)There are differences in the rhizosphere bacterial community diversity among four cultivars of 'Zifengyu','Dafugui','Yangfeichuyu' and 'Xiangyangqihua'.Among them,the a diversity of'Dafugui' is the highest,while that of'Zifengyu' is the lowest.The dominant flora of the rhizosphere soil of the four peony cultivars are Proteobacteria and Acidobacteriota.Soil factors have an important influence on the distribution of peony rhizosphere soil microbial communities,and pH,alkaline phosphatase and urease have the greatest influence on it.(2)Thirteen strains of ACC deaminase PGPR were isolated from peony rhizosphere soil using ACC as the sole nitrogen source medium,and named YDSY1-YDSY13.After the identification of colony morphology,physiological and biochemical indicators and molecular biological identification of 16S rDNA,the results of thirteen strains were Chryseobacterium flavum,Klebsiella sp.,Pseudomonas sp.,Erwinia sp.,Pantoea cypripedii,Pseudomonas oryzihabitans,Pseudomonaspsychrotolerans,Herbaspirillum sp.,Pectobacterium cypripedii,Pantoea sp.,Citrobacter sp.,Klebsiella michiganensis and Klebsiella pneumoniae.(3)The characteristics of 13 strains obtained were analyzed,and found that all the 13 strains had ACC deaminase activity,among which YDSY8,YDSY11 and YDSY12 had the strongest activity.In addition,5 strains(YDSY8,YDSY2,YDSY12,YDSY7,YDSY6,YDSY9,YDSY11,YDSY13 and YDSY5)had the ability to produce IAA,and 7 strains(YDSY7,YDSY4,YDSY6,YDSY9,YDSY11,YDSY13 and YDSY5)had the ability to synthesize ferrophilin.Eight strains(YDSY3,YDSY4,YDSY11,YDSY2,YDSY13,YDSY12 and YDSY1)had the ability to dissolve phosphorus.(4)Three strains with good growth promoting properties,YDSY8(Herbaspirilum sp.),YDSY11(Citrobacter sp.)and YDSY12(Klebsiella michiganensis)were integrated into the rhizosphere of P.lactiflora,and it was found that the three strains could all increase the morphological indexes(plant height,stem diameter,fresh weight,dry weight)and physiological indexes(SPAD,SOD POD,CAT,soluble sugar and soluble protein content)of P.lactiflora.YDSY8 had the best growth-promoting effect.