Isolation And Identification Of Endophytic Bacteria And Their Potential For Biocontrol In The Sandy Acacia

Sambucus is a Tibetan medicinal plant unique to Tibet,which is rarely infested by external pathogens,presumably related to the active substances produced by the endophytic bacteria contained in its body.Endophytic bacteria are widely distributed and diverse,and have played a great role in the biological control of plant diseases.The aim of this study was to isolate and screen antagonistic bacteria with strong antibacterial activity from the tissues of Sophora japonica,to provide a basis for the development and utilization of endophytic bacteria of Sophora japonica,and to lay the foundation for the biological control of crop diseases.The main contents and results of this study are as follows.1.135 strains of endophytic bacteria were obtained by tissue isolation and plate coating method from leaves and fruit pods(flowers)of Sophora japonica at different growth periods in Linzhi,Tibet.Among them,16 endophytic bacteria were isolated from leaves and 26 endophytic bacteria were isolated from flowers during the flowering stage of Acacia sagittata;11 endophytic bacteria were isolated from leaves and 5 endophytic bacteria were isolated from fruit pods during the pod setting stage of Acacia sagittata;36 endophytic bacteria were isolated from leaves and 41 endophytic bacteria were isolated from fruit pods during the fruit ripening stage of Acacia sagittata.The number of endophytic bacteria in fruit ripening stage > endophytic bacteria in flowering stage > endophytic bacteria in pods,and the number of endophytic bacteria in fruit pods(flowers)> endophytic bacteria in leaves showed a trend.2.Using the plate confrontation method,we screened the endophytic bacteria with inhibitory effects on wheat root rot,wheat blast,wheat blast,quinoa mycorrhizal fungi,grape ulcer,apple brown rot,apple rot,pear brown rot,rice blast,rape mycorrhizal fungi,plum brown rot,and found that 15 out of 135 endophytic bacteria of the sandy locust were able to antagonize at least one Among them,strains Y1-5 and Y2-11 had the broadest spectrum of inhibition and strong inhibition activity.3.15 strains of endophytic bacteria of Acacia spp.with significant antibacterial activity were identified by a combination of morphological,physiological and biochemical tests and molecular biology.The results revealed that 13 strains were of the genus Bacillus,of which strains Y1-4,Y2-1,Y2-7,Y2-6,Y2-11 and Y4-15 were Bacillus subtilis and strains Y2-2,Y2-3 and Y2-10 were Bacillus atrophyticus;strain Y1-5 was Bacillus saffronis;strain Y4-19 was Bacillus nanhai;strain G1-4 was Bacillus tequila The diversity of endophytic bacteria with antibacterial properties on different tissues in the flowering,podding and fruit-ripening stages of locust was then analyzed by calculating the diversity index.The results showed that the diversity of endophytic bacteria was the highest in the leaves of the maturing leaves of Sophora japonica,and the diversity of endophytic bacteria in the leaves of the flowering and podding stages was not very different.4.In vitro experiments were used to explore the disease prevention and treatment effects of strains Y1-5 and Y2-11 on apple brown rot.The results showed that the preventive effect of Y1-5 on apple brown rot reached 39.33%,and the curative effect on apple brown rot reached58.87%;the preventive effect of Y2-11 on apple brown rot reached40.88%,and the preventive effect of apple brown rot was 40.88%.The curative effect of the two strains reached 59.04%.After significant analysis,it was found that the two strains were not as effective as the drug control in the experiment of preventing apple brown rot.However,in the experiment of treating apple brown rot,the two strains of Although the curative effect is not as good as the treatment effect of triadimefon compared with the medicine,it is equivalent to the treatment effect of carbendazim.