Identification,biological characteristics of southern blight pathogen of Baccaurea ramiflora and fungicides screening
Southern blight of Baccaurea ramiflora occurred frequently in the seedling raising process,which seriously affected the propagation of B.ramiflora seedlings.To clarify the types of pathogen,the biological characteristics,and control fungicides,the tissue culture isolate method was applied to isolate the pathogen.Koch's postulates were used to validate the representative strains.The types of pathogens were clarified by combining morphology and molecular identification methods.Growth conditions of the pathogen under differ-ent culture media,pH values,cultivation temperatures and lights were determined.Indoor toxicity of six fun-gicides such as tebuconazole SC was tested.The results showed that the four strains of pathogens numbered MNG1-MNG4 were obtained based on the similar morphological features.The representative strain MNG-1 was selected for the pathogenicity test that it fulfilled the Koch's postulates.The pathogen MNG-1 was identi-fied as Athelia rofsii by morphology analysis and comparative analysis of amplified DNAs of pathogenic bacte-ria by primers ITS,TEF,SSU and LSU.The results of biological characteristics determination showed that the optimum growth temperature and pH value for mycelium was 30 ℃ and 7,respectively.The optimal medi-um was PSA.The optimum conditions for the generation of sclerotium were low temperature,alkaline and continuous light.Among the 6 fungicides,thiafuramide had the best inhibitory effect on MGN-1 mycelium,with the EC50 of 0.036 mg·L-1,followed by tebuconazole,with the EC50 of 0.463 mg·L-1.Hymexazol,thiophonate-methy,chlorothalonil and mancozeb showed poor inhibitory effect on southern blight pathogen.
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