Identification Of Potato Common Scab Pathogens In Heilongjiang Province And The Biocontrol Application Of Bacillus Amyloliquefaciens ZDl38

Potato is the fourth largest food crop in the world after rice,corn and wheat.It has played an important role in the Chinese people’s poverty alleviation and the increase in the income of China’s food industry.However,Potato Common Scab（PCS）is becoming more and more serious,and the damage in several major potato producing areas in China is increasing year by year,causing serious deterioration of potato appearance and quality,resulting in serious impact on potato economic benefit S.As one of the main potato producing areas in northern part of China,the incidence of potato scab is particularly serious in Heilongjiang province.Since there is still no effective measures to prevent and control potato scab,a green and efficient control measure is urgently needed to reduce the potato scab.In this study,through extensive sampling of potato scab-prone areas in Heilongjiang Province,the actinomycetes screened from potato scab were sorted out and systematically identified.Seedling method,16S r RNA gene and toxin gene test were used to identify the pathogenic strains,master its main pathogenic types,distribution and taxonomic statu S.Using the main pathogenic strains for target,the biocontrol strains were first screened and re-screened by the plate confrontation method and the Oxford cup test method,and the biocontrol strains were identified by morphological observation,physiological and biochemical characteristics,BIOLOG test and 16S r RNA test,and their biocontrol effects were further verified in pot experiment.The optimization experiment of fermentation provided possible for the development of biocontrol agents,and also layed application foundation for the control of potato scab.The main research results were as follows:（1）59 isolates of actinomycetes were obtained from the samples collected in Heilongjiang Province,including 2 isolates in Daqing,6 isolates in Harbin,31 isolates in Qiqihaha,6 isolates in Jiamusi,6 isolates in Mudanjiang,and 2 isolates in Shuangya,5isolates in Suihua.（2）There were 5 types of PAI pathogenicity island genotypes,including 5 strains with genotype txt AB⁺/tom A⁺/necl⁺,and 1 strain with genotype txt AB⁺/tom A^-/necl⁺,3 strains with of genotype txt AB⁺/tom A^-/necl^-,4 strains with genotypes of txt AB^-/tom A⁺/necl^-,and 4 strains with genotypes of txt AB^-/tom A^-/necl⁺.（3）According to the 16S r RNA test,the pathogenic bacteria isolated from the collected samples,the main pathogenic bacteria of potato scab in Heilongjiang Province were S.scabiei,S.griseus and S.galilaeus,of which S.scabiei was the dominant strain,so we chose S.scabiei6-2-3 for further experiment S.（4）The pathogenicity detection of S.scabiei 6-2-3 by small potato chip method,radish seedling method,toxin gene detection,and pot test,all showed that strain 6-2-3 had potato scab pathogenicity.Morphological observation,physiological and biochemical characteristics,BIOLOG and 16S r RNA test were carried out,the identification result showed the pathogenic bacterium 6-2-3 was Streptomyces scabiei.（5）Two biocontrol strains NO.38 and NO.180 with excellent antagonistic effect against the pathogenic bacteria of potato scab were screened out through the primary screening and re-screening.The strains 38 and strain 180 were identified by morphological observation,physiological and biochemical characteristics,BIOLOG and 16S r RNA test,and it was found that the biocontrol strain 38 was belong to Bacillus amyloliquefaciens,and antagonist strain180 was belong to Bacillus vallismorti S.（6）The pot experiment found that the biocontrol effect of strain 38 against potato scab reached 83.35%,while the biocontrol efficiency of strain 180 was 45.95%,which was lower than that of strain 38.The results of pot experiments proved that antagonistic bacterium 38significantly reduced the incidence,incidence grade and incidence coefficient of potato scab,and showed excellent biocontrol effect.Therefore,this biocontrol bacterium was named Bacillus amyloliquefaciens ZDL38 and the fermentation optimization was carried out next.（7）Single factor test was carried out on Bacillus amyloliquefaciens ZDL38,and the best carbon source of fermentation medium of strain ZDL38 was determined as bran,and the nitrogen source was soybean meal,the inorganic salt was Na Cl,the temperature was 32℃,the p H value was 6,the fermentation time was 36 h,and the inoculation amount was 4%.The optimal fermentation conditions for obtaining strain ZDL38 were bran 2%,soybean meal4.5%,Na Cl 0.3%,temperature 32℃,p H 6,fermentation time 36h,and inoculum volume 5%.It was verified that the maximum bacterial volume was 4.27×10~9CFU/m L.