Study On Antagonism Of Actinomycets Against Potato Fungal Diseases

Potato is the main grain crops in Gansu province, planting areas increases year byyear. The potato fungal diseases which widespread occurrence and the seriouslyinfluent on the yield and quality, which becomes one of the major factors limiting thedevelopment of the potato industry. Mainly used chemical pesticide to control thepathogenic fungi in the current production, not only pollute the microbial environmentand cause pathogens become resistant, but also expose a threat to human health.Biological control can avoid the above shortcomings, and effective safety preventionand control of diseases.The main purpose of this study was based on the four potato pathogens as targetpathogens，isolating and screening the Actinomycetes with antibacterial effect fromsoil samples of the main production areas of potato. Classification and identificationof the antagonistic actinomycetes strains was made and the antibacterial effect ofantagonistic strain with fungicides was compared, preliminary study ofthe antibacterial mechanism of antagonistic actinomycetes.The following mainconclusions:1、Iolation and filtration antagonistic actinomycetes. A total of92actinomyceteswere isolated from soil samples collected from the main production areas of potato ofGansu province. The8strains of actinomycete isolated from92actinomycetes,which have a antimicrobial action against Fusarium spp,Rhizoctonia solani,Colletotrichum coccodes (Wallr.)Hughes and Alternaria solani Sorauer throughplate external screening, the average antibacterial circle diameter was greater than10mm; using the method of the fungi growth rate rescreening the8actinomycetes thatthe strains grew well above, the results show the strain WY02、DX23、D01、D12andTS01has strong and relatively stable inhibiting effect to four pathogens，theantibacterial rate can reach more than70%.2、Do preliminary isolate and identify on Screening of strain. According to thecharacteristics of morphological, cultural, physiological and biochemical, as well as16SrDNA sequence, the strain D01was identified as Streptomyces griseus, the strainD12was identified as Streptomyces sp., the strain DX23was identified asStreptomyces badius, the strain TS01was identified as Streptomyces bambergiensis, the strain WY02was identified as Stenotrophomonas maltophilia, four strains areStreptomyces, one strain is Stenotrophomonas.3、Compared the antibacterial effect of antagonistic strain with fungicides. theresults show that25%Amistar SC has greatest antibacterial effect in the four kinds offungicides, and antibacterial effect of four actinomycetes to two pathogens wasdistinctly higher than25%Amistar, especially the strains DX23has obviouslyantibacterial effect, When diluted concentrations were0.19ug/ml and0.18ug/ml, theantibacterial rate of Rhizoctonia solani and Alternaria solani Sorauer can amount to50%, in effective concentration of5ug/ml antibacterial rate can reach more than80%.4、 Sensitivity bioassay of antagonistic actinomycetes. Choose four kinds offungicides and pesticide that use more often and use a long time in the production ofpotato, the susceptibility of four antagonistic actinomycetes against chemical agentwas assayed by inhibition zone method, the results showed that the strain DX23demonstrated prominent sensitivity to the80%mancozeb WP and58%metalaxyl WP,when other strains showed slightly sensitive or insensitive to the fungicides andinsecticides.5、Preliminary study the antibacterial mechanism of antagonistic actinomycetes.Theresults of regeneration capacity and microexamination of inhibiting hypha showedthat all tested actinomycetes had represented persistent inhibiting effects on the targetpathogens in different degrees; observed inhibiting hypha found that actinomycetesstrains might producted or secreted somewhat to cause the target fungal hyphaeaberrated.