Screening Of Biocontrol Bacteria And Preliminary Study On Its Biocontrol Mechanism In Potato Common Scab

Potato common scab is an important soil-borne disease,and commonly occurs in potato growing regions in the world.It is mainly caused by Streptomyces spp.This disease seriously affects the appearance quality of the potato,reduces the commodity value of the potato block,and poses a great threat to the production of the potato.From the perspective of biological control,this study screened the microbial resources that had biocontrol effect on pathogen of potato common scab,laid the foundation for effective prevention and control of potato common scab,and provided theoretical basis for the development of future biocontrol agents.The results were as follows:Soil and infected potatoes tubers were isolated from 4 serious fields of potato common scab for biocontrol bacteria.A total of 53 actinomycetes were obtained.After screening,6 strains were found to have different antagonisms against the PS1.Antagonistic bacteria,through the determination of antagonistic activity,potted plants and field control efficacy,finally screened out two strains N3 and N23 with the best control effect.The field control effect of strain N3 was 75.15%,and the yield increase effect was up to 10.03%;the field control effect of strain N23was 73.26%,and the yield increase effect was 8.01%.Two kinds of inoculation methods,soaking seeds and furrows,were compared.The best inoculation method for strain N3 was furrow application,and the inhibitory effect was 75.15%;the best inoculation method for strain N23 was soaking,and the inhibitory effect was 73.26%.According to the inhibition spectrum,strain N3 had a very good inhibitory effect on the growth of Rhizoctonia solani AG-3,Inhibition rate was 79.0%,and,there is no inhibition on several pathogens Fusarium oxysopoyum,Erwinia carotovora subsp.atroseptica and Erwinia carotovora subsp.atroseptica caused potato disease.Based on the identification techniques of colony characteristics,morphology,physiological and biochemical characteristics,and molecular biology,the biocontrol strain N23 was identified as Bacillus methylotrophicus and the biocontrol strain N3 was identified as Bacillus subtilis.The biological characteristics of biocontrol strain N3 showed that the optimum carbon source for N3 growth was soluble starch,the most suitable nitrogen source was Potassium sulfate,the optimum growth pH was 7.5;the strain N23 showed that the optimum carbon source for N23 growth was soluble starch,the most suitable nitrogen source was ammonia nitrate,the optimum growth pH was 7.5.The optimum growth temperature was 32?.The results of the biocontrol mechanism of the biocontrol strain N3 and N23 showed that no volatile compounds were found to inhibit the growth against the pathogen PS1.Non-volatile substances had a significant inhibitory effect on the growth of PS1 and the inhibition rate reached separately 69.23%and 79.0%.The indoor potato sprouting test and the two-year field experiment results showed that two stains cound increase the emergence rate of the potato,increase the growth potential,have a certain promoting effect,and cound increase the yield.