烟草根黑腐病生防内生菌的筛选、鉴定及其防治效果分析OA

[Objective]The study isolates endophytic bacteria from tobacco roots that have a good control effect on the tobacco root black rot pathogen,thereby providing biocontrol resources and a reference basis for the prevention and control of this disease.[Method]A plate con-frontation assay was used and endophytic bacteria with inhibitory effects against Thielaviopsis basicola were screened.The strain exhibiting the highest inhibition rate was subjected to morphological observation,physiological and biochemical tests(including sugar alcohol fermentation,methyl red test,Voges-Proskauer test,and starch hydrolysis),and 16S rRNA gene sequencing for species identification.Subsequently,its sta-bility under different temperatures,NaCl concentrations,and UV irradiation was evaluated.Additionally,the strain was assessed for its antimi-crobial spectrum,as well as its abilities to produce indole-3-acetic acid(IAA),solubilize phosphate,release potassium,and secrete protease,cellulase,and siderophores.[Result]Four bacterial strains with antagonistic activity against T.basicola were obtained by plate confrontation screening.Among them,strain YNLT3 exhibited the highest inhibition rate of 69.64%.Morphology,Gram stain,and physiological-biochemi-cal analyses indicated that this strain belonged to the genus Bacillus and was Gram-positive.It showed good tolerance to high temperature,UV radiation,and high salinity.Physiological and biochemical properties,together with 16S rDNA sequence alignment analysis,led to the identifi-cation of strain YNLT3 as Bacillus licheniformis.The strain displayed a broad antimicrobial spectrum and was capable of secreting protease and cellulase,producing siderophores and IAA,and solubilizing phosphate and releasing potassium.The labeled strain YNLT3R successfully colonized the tobacco rhizosphere soil and maintained a stable population.Following root drenching treatment with the fermentation broth of YNLT3,leaf number,plant height,root fresh weight,and root dry weight increased significantly by66.7%,40.0%,38.3%and45.2%,re-spectively,compared to the control.The activities of the key defense enzymes POD,PAL and CAT at their peak were 141%,131%and 271%higher than those of the control,respectively.The pot control efficacy of strain YNLT3 against tobacco root black rot reached 51.68%.[Conclusion]The endophytic bacterial strain YNLT3 exhibits promising biocontrol potential against tobacco root black rot and also shows a certain plant growth-promoting effect.