Isolation And Identification Of Pathogenic Bacteria Of Root Rot Of Cerasus In Guizhou And Research On The Effect Of Antagonistic Antibacterial Prevention And Control

In recent years,root rot of Cerasus has occurred in many places in Guizhou,causing a large number of cherry blossom deaths and causing huge economic losses.However,due to the lack of clear pathogens and the lack of targeted prevention and control methods,the disease still shows a rapid expansion trend.In the past,chemical agents were usually used for disease control,but long-term and large-scale application of fungicides will cause the 3R(resistance,rampant resurgence and residual residue)problem of pesticides,and chemical agents can no longer meet people’s requirements for plant disease control.Because of its advantages of green and pollution-free and long-term effectiveness,biological control has gradually become the mainstream of prevention and control methods.In this study,the pathogens were isolated by tissue isolation,and the pathogens of cherry blossom root rot were identified by using the Koch’s rule.From the wild health and diseased cherry blossom rhizosphere soil,the biocontrol bacteria with control effect on cherry blossom root rot pathogens were screened.Finally,the control effect and mechanism of screened biocontrol bacteria in the control of cherry blossom root rot were studied.The main results of the study are as follows:(1)In Wudang District,Guizhou Province,cherry blossom plant roots with typical root rot symptoms were selected,and the pathogenic bacteria were isolated and purified by tissue separation method,and the pathogenicity of the isolated strains was detected by backconnection.Results Fifty-four fungi were isolated from tissue,and 4 strains(YH5,YH15,YH19,YH26)in the backconnection test could produce symptoms of cherry blossom root rot.Among them,strain YH15 is the most pathogenic,and its incidence reaches 100%,which is higher than that of the other 3strains.In addition,the hyphae and spores of the strain were observed morphologically to identify Fusarium spp.,and then the genetic sequences of ITS and?-tubulin genes of the strain were amplified and the genetic sequences were compared and analyzed,and the strains YH5,YH15 and YH19 were identified as F.oxysporum,strain YH26 identified as F.solani。(2)The bacteria of healthy and diseased cherry blossom rhizosphere soil were isolated by dilution coating,and biocontrol strains were screened by confrontation.As a result,a total of 83 strains of bacteria were isolated,and 5 biocontrol bacteria with strong antibacterial activity were screened in confrontation experiments,and the corresponding strains and antibacterial rates were as follows: SF1-2(75.19%),SF1-15(43.67%),SF1-16(41.61%),SF2-3(44.19%),SF3-16(46.77%),respectively.The morphological and molecular identification of five biocontrol bacteria was as follows:SF1-2 as Pseudomonas chlororaphis,SF2-3 as Pseudomonas sp.,SF1-15 and SF1-16 as Ensifer adhaerens,SF3-16 as Cupriavidus sp.,among which P.chlororaphis has an inhibitory rate of 75.19%,with the highest inhibition rate.The prevention and control effect of biocontrol bacteria SF1-2 on cherry blossom root rot was detected in pot experiments and found that the incidence of cherry blossom root rot of the retrogenic bacterium YH15 was 70%,and the disease index was 50%,while the incidence of cherry blossom root rot of the retrospective pathogen SF1-2 was 30%,and the disease index was only 7.5%,and the relative control effect reached 85%.(3)The study on the prevention and control mechanism of strain SF1-2 on cherry blossom root rot showed that strain SF1-2 could inhibit pathogenic bacteria through metabolites,and the inhibition rate of non-volatile metabolites of strain SF1-2on strain YH15 was 16.33%.Its non-volatile metabolites were analyzed to obtain its22 components,and combined with previous literature reports,the analysis of strain SF1-2 can produce pyrrole,which may plays an important role in the process of inhibiting pathogenic bacteria.Strains SF1-2 can act on the hyphae of the pathogenic bacterium YH15,causing hyphae formation to dissolve and break.In addition,strain SF1-2 affected the physiological,biochemical,soil physicochemical properties and soil microbial colonies in the process of improving the control effect of cherry blossom root rot.The details were as follows: strain SF1-2 could increase the soluble sugar content of cherry blossom roots and reduce the content of MDA,and strain SF1-2 treatment could increase root vitality.The strain SF1-2 could significantly affect the total nitrogen content of rhizosphere soil,and the total nitrogen content was significantly increased.The treatment of strain SF1-2 significantly reduced the soil urease content.Compared with pathogenic bacteria alone,strain SF1-2 treatment changed the number of fungi and species composition in the rhizosphere soil,and also changed the number of bacteria.Specifically,compared with the pathogenic bacteria alone,SF1-2 treatment upregulated the number of Trichosporon spp.,Paraphaeosphaeria,and Pleurotheciella,and reduced the number of Cercophora spp.,Nectria spp.,Cladosporium spp.,Gilmaniella spp.,Mariannaea spp.,Paracremonium,Acinetobacter spp.,Chryseolinea,Paracoccus spp.,and Flavobacterium spp.