| Potato is the fourth largest food crops after wheat,corn,rice in the world,and known as "earth’s future food" for its rich nutrition as well as it’s high dietary fiber,and it has been become the staple food in many countries.Potato common scab(PCS)is caused by plant pathogenic Steptomyces spp.,a serious soil borne disease in potato production.The disease is very common in the potato growing areas and gradually sharpened by years.The development of potato common scab has became increasingly serious in the main potato-growing areas in China,but now,the this disease is lack of effective prevention and control measures.A strain of Streptomyces,AMCC400023,was isolate from potato common scab disease spot.Then we carried on pathogenic detection and system identification for this pathogen,and put this pathogenic bacteria as target material to screening antagonistic bacteria from the endophytic bacteria isolated from the potato,and further testing the bio-control effect of antagonistic bacteria on AMCC400023 pathogens by pot experiment.We also carried on the system identification and the inhibitory action of antibacterial spectrum measurement,at the same time we studied the enzyme production characteristics and antibacterial material stability of the antagonistic bacteria which we screened.The main results as follows:(1)A strain of Streptomyces AMCC400023 was isolated from potato common scab disease spot,pathogenicity test showed that the separation of Streptomyces strain possesses pathogenicity of causing a scab and can form typical potato scab in the potato skin.The polyphasic taxonomy system identification of Streptomyces strains AMCC400023 came out that it is Streptomyces bottropensis.(2)Seventy-eight endophytic bacteria strains were isolated from the healthy potato pieces,twenty-one strains of these strains get the inhibitory action by filter method preliminary screening.Three of them Ua,Me,Ma were tested by Oxford cup method,and the result show they all have good inhibition effect.Fifteen times of transgenerational cultivation of three strains bacteriostatic showed that the antibacterial effect still remained stable,which remains that the genetic stability of these three strain were good.(3)Pot experiment showed that the bio-control effect of antagonistic strains Ua and Me to potato common scab can reached 53.36% and 53.36% respectively,but Ma strain is only 30.03%.In the autumn cultivation experiments,the bio-control effect of antagonistic strains Ua and Me to potato common scab reached 67.92% and 64.98% respectively,bio-control effect and stability were better than spring slightly.Pot experiment results showed that potato common scab’s incidence,pathogenesis grade and coefficient were significantly reduced after treated by Ua and Me strains,so these two strains have good bio-control effect.The bio-control effects of the two pot experiments were stable.The number of microbes in potato rhizosphere shows that the total number of bacteria significantly increased after treated by adding Ua and Me fermented liquid while the number of actinomycetes decreased significantly.(4)The polyphasic taxonomy system identification of Ua and Me strains shows that they were Bacillus methylotrophicus.The filtration sterilization solution of antagonistic strains Ua and Me have certain bacteriostatic effect on 9 strains pathogenic fungi,and also have certain bacteriostatic effect on the nonpathogenic Streptomyces,but the bacteriostatic effect is significantly lower than scab pathogenic Streptomyces.(5)The antibacterial substance of antagonistic strains Ua and Me still keep good antibacterial activity after deal with different temperature,pH and organic solvents processing,which showed that the stability of antagonistic strain of antibacterial substance is good.Enzyme activity assay showed that antagonistic strains,Ua and Me,have protease and cellulose enzyme activity,but don’t have chitin and pectinase enzyme activity. |
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