Identification Of Antagonistic Strain TG116 Against Plant Pathogenic Fungi And Study Of Its Biological Characteristic And Biocontrol Mechanism

Crops yield decrease and postharvest loss that caused by plant fungous diseases are the key problems hindered agricultural production.Biological control of plant fungous diseases attracts more and more attention because of its safety for the environment,no pollution,high specificity and no drug resistance in the application.Endophytes can prevent crops from plant fungous diseases,some of them have already been invented into the biological pesticide for agricultural production.Typhonium giganteum Engler has extensive pharmacological actions and abundant chemical constituents,meanwhile,non-susceptibility to diseases and insect pests in the process of growth.We speculated that the endophyte which had long term co-evoluted with Typhonium giganteum Engler may also had some uniqueness and research value.Previous studies also showed that medicinal plants contained abundant biocontrol bacteria,but the research about endophyte from Typhonium giganteum Engler has not been reported.In order to provide new strain resources for biological control of plant fungous diseases,this study isolated the endophyte from Typhonium giganteum Engler and got an endophytic bacterium named TG116, which had good antagonistic effect on plant pathogenic fungi.Antifungal spectrum and characteristic to plant pathogenic fungi of strain TG116 were studied.Its biocontrol potential had been further verified and explored by pot disease prevention experiment. Strain TG116 was identified according to morphological,physiological and biochemical,molecular biology methods.Its biological characteristic and biocontrol mechanism about plant fungous diseases were also preliminarily studied in this paper.The results were as follows:(1) Strain TG116 was a broad-spectrum antagonistic bacterium that could be antagonistic to all the tested plant pathogenic fungi,with mycelium of plant pathogenic fungi protoplasm leakaging,hollowing,distorting and deforming.Soaking seed and pouring root with TG116 cultures both had good control effects in pot disease prevention experiment.The longer interval time of inoculating pathogen was, the better effects of disease control could have.Meanwhile,the metabolite and cell of TG116 both had some disease control effects.(2)Strain TG116 was consistent with Bacillus licheniformis in respect of the morphological,physiological and biochemical characteristics.The analysis results of 16 S rRNA sequences showed that its homology with Bacillus licheniformis was up to 99 %.Therefore,strain TG116 was identified as Bacillus licheniformis.(3) The logarithmic phase for cell growth of strain TG116 was the period between 8 to 16 hours,then the stationary phase(after 16 hours),at last,the decline phase(after 48 hours);the optimum inoculation dose was 1 %;it could be grown between the temperature from 20 to 60 ℃ and the optimum temperature was 45 ℃;also,it can be grown between the pH from 3.0 to 9.0 and the optimum pH was 7.0;it showed best growth under the osmotic pressure of 1 % NaCl;the best utilization of carbon and nitrogen were cellobiose and yeast extract,respectively;strain TG116 had a strong ability to adapt to the environment.(4) In a certain period,the PAL、POD and PPO activities in cucumber leaves which was induced by strain TG116 were significantly higher than that of no induced treatment.Besides, co-inoculated with plant pathogenic fungi lead to higher increase in the activities of PAL、POD and PPO than strain TG116 single treated.It indicated that co-inoculated with plant pathogenic fungi was good for strain TG116 to induce plant systemic resistance.Although separate inoculated with strain TG116 could increase the activity of SOD,the effect was not obvious and the content of MDA changed a little bit and was slightly lower than control treatment in cucumber leaves.Strain TG116 could secrete protease and cellulase.We speculated that the biocontrol mechanism of strain TG116 to plant fungous diseases were associated with increased the activities of PAL、POD and PPO,reduced the content of active oxygen substances,mitigated the degree of membrane lipid peroxidation,secreted enzymes which could degrade the cell wall of plant pathogenic fungi.