The Screening Of Biocontrol Bacteria Against Fusarium And Verticillium Wilts Of Cotton And Its Researches On Disease Resistence Mechanism

Fusarium Wilt and Verticillium Wilt are two major diseases in cotton production.The pathogen of them is Fusarium oxysporum f.sp.vasinfectum Atk.Snyder et Hansen and Verticillium dahliae Kleb and Verticillium albo-atrum Reinke & Berth.Biological control has the advantages of green environmental protection,stable control effect,long effective period,and plays an important role in the process of integrated crop control.In order to obtain a significant antagonistic biocontrol strain against Fusarium Wilt and Verticillium Wilt.In this study,the rhizosphere soil of cotton was collected from the main cotton producing areas in the province,and the strains that had biocontrol effect on Fusarium Wilt and Verticillium Wilt were screened and identified,and its bacteriostatic mechanism was preliminarily explored.The results are as follows.1.47 soil samples were collected from Dongying,Liaocheng,Jining,Dezhou,Jinan and other places in Shandong Province.Six strains with good resistance were screened by antagonizing the pathogens with biocontrol bacteria in the flat plate.The strain JNJX-2 was selected,which had the best inhibitory effect on Fusarium Wilt and Verticillium Wilt.It was identified as P.polymyxa by physiological and biochemical determination and molecular biological identification.The growth curve of strain JNJX-2 and the optimum growth temperature were determined.The identification of extracellular protease showed that it could secrete chitin hydrolase,protein hydrolase,pectin hydrolase and cellulose hydrolase.2.Four different inoculation methods were explored.It was found that the pathogenic effect of root irrigation was the best.Pot experiment in laboratory proved that the suspension of biocontrol JNJX-2 had certain control effect on Fusarium wilt and Verticillium wilt.3.The bacteriostatic spectrum of JNJX-2 was determined by laboratory culture.The results showed that it had a good bacteriostatic effect on Staphylococcus aureus,Escherichia coli,Botrytis cinereaan and Bipolaris sorokiniana.4.The bacteriostatic substances of JNJX-2 were extracted by ammonium sulfate precipitation and extraction and steaming.It was found that the properties of the crude extracts were stable and were not sensitive to temperature,ultraviolet,and protease.5.The activity of protective enzymes in cotton seedlings treated with Fusarium and Verticillium wilts and JNJX-2 showed that the use of strain JNJX-2 could increase the activities of PPO,PAL,POD and SOD.The suspension of strain JNJX-2 can also promote growth.