Isolation And Identification Of Antagonistic Microorganisms In Potato Rhizosphere Soil And Preliminary Study On Their Biocontrol Effect

Potato,,is the world's fourth largest food crop.Promotion of potato farming as a staple food in China,the continuous expanding planting area makes it very difficult for crop rotation.Years of continuous cropping has led to the occurrence of potato soil-borne diseases,which seriously affected the yield and quality of potato.At present,due to the lack of disease-resistant varieties,chemical control is the main method use to control and prevent potato soil-borne diseases,but chemical control can easily lead to pesticide residues in the soil,causing damage to the ecological environment.Therefore,in this study,the rhizosphere soil and soil collected from potato plots with farmyard manure was used as experimental materials.These potato plots are located in Dajing village.Xumajao village and Honggeertu village.The antagonistic microorganisms were isolated,screened,identified and studied based on their biological characteristics.The results were as follows:1.A total of 1465 microbial strains were isolated from Dajing village.Xumajao village and Honggeertu village,with 1391 bacterial strains and 74 actinomycetes.Using the plate confrontation test,71 strains with antagonistic effect against verticillium wilt and fusarium wilt of potato were screened at the preliminary stage.The screening results of broad-spectrum antagonistic strains showed that XS142,XS146,XS107,XS156 and DS86 strains all had certain antagonistic effects on Verticillium wilt of potato,Fusarium wilt of potato,Potato late blight and Black scurf of potato,so these five strains were selected as candidate strains to study their biological and control effects.2.The results of the study on the biological control effect of the above alternative strains by means of root grafting on potted plants showed that the inoculation of Verticillium wilt of potato and Fusarium wilt of potato by strain XS142 after pretreatment showed the lowest mean disease index(12.50,15.00)and the strongest antagonistic effect.The second was strain XS146,and the mean disease index of the two pathogens was 22.92 and 23.33,respectively.The mean disease index of XS156 of the two pathogens after pretreatment was higher,which was 45.83 and 50.00,respectively.3.Through morphology and 16SrDNA sequence analysis,Strains XS142 and XS146 were identified as Bacillus velezensis;strains XS156 and XS1007 were also identified as Bacillus amyloliquefaciens.The bacterial strain DS86 was identified as Paenibacillus polymyxa.4.In the phosphorous dissolution experiment,DS86,XS156 and XS107 strains could form an obvious clear phosphorous dissolution circle with a diameter.During the antibiotics screening test,all five strains used as biocontrol could be grown on different concentrations of hypopycin.