Identification And Biocontrol Of Five Endophytic Bacteria In Jujube Leaves

In recent years,Jujube Black Spot disease in southern Xinjiang has seriously affected the quality and yield of jujubes in Xinjiang.Biological control meets the needs of environmental protection,food safety and human health,and is an ideal substitute for chemical fungicides.Obtaining high-efficiency biocontrol bacteria is the basis of biological control.Plant endophytic bacteria can promote plant growth and inhibit pathogenic bacteria,and are an excellent biological resource bank.In this study,jujube leaves were used as materials,and endophytic bacteria were isolated and cultured to determine the taxonomic status of endophytic bacteria in jujube leaves in southern Xinjiang,screened endophytic bacteria with bacteriostatic activity,and explored the reasons why endophytic bacteria inhibit pathogenic bacteria.The development and utilization of endophytic bacteria in jujube as microbial agents provides a theoretical basis for the biological control of fruit tree diseases.The main contents and results of this study are as follows:1.The endophytic bacteria were isolated from healthy jujube leaf tissue by means of plate streaking.According to the characteristics of colony color,shape,size,luster,transparency,and whether the edges are neat or not,a total of 5 endophytic bacteria with different appearance and morphology were obtained.Combining morphological,physiological and biochemical tests and molecular biology methods for identification: strain ju01 is Kocuria oceani;strain ju02 is Kocuria rosea;strains ju03 and ju04 are Arthrobacter oryzae;strain ju05 is Chryseobacterium indologenes.2.The 5 strains of jujube leaf endophytic bacteria were tested against Jujube Black Spot(Alternaria alternata),Walnut Black Spot(Alternaria alternata),Walnut Rot Fungus(Cytospora Chrysosperma)and Apple Valsa Canker(Valsa mali)and Pear Black Spot(Alternaria tenuissima)were tested for bacteriostasis,the results showed that except ju01,ju02,ju03,ju04 strains had no antagonistic effect on Walnut Rot Fungus,strain ju05 had no antagonistic effect on Apple Valsa Canker,and endophytic strains had no antagonistic effect on other strains.The target pathogenic fungi have a certain degree of antagonism,and the antibacterial rate is between 50.42% and79.83%.In terms of inhibiting conidial germination of pathogenic bacteria,the five endophytic bacteria all had different degrees of inhibiting conidial germination of Jujube Black Spot at 4h,14 h and 24 h,and strain ju01 had the best effect at 24 h.The inhibition rate was 60.75%.By observing the growth changes of pathogenic hyphae,it was found that ju01,ju03,ju04,and ju05 strains had a destructive effect on the target pathogenic hyphae,making the normally growing hyphae thin,distorted,and cracked.3.The metabolites of 5 endophytic bacteria were detected and analyzed by LC-MS(Liquid Chromatography Mass Spectrometry),and the detection results showed that the 5 endophytic bacteria produced metabolites with antibacterial activity,which proved that the 5 endophytic bacteria produced metabolites with antibacterial activity.Bacteria are feasible as the development of microbial inoculants,and have great development and application value in the field of biological control.