Identification on pathogen of Menispermum dauricum target spot and study on its biological characteristics and fungicide susceptibility / 中草药

ABSTRACT

Objective: To identify the pathogen of Menispermum dauricum target spot (a new plant disease in China) and study its biological characteristics and susceptibility to fungicides. Methods: Tissue isolation method was used to obtain the isolates from diseased-leaf. The pathoginicity of the isolates was fulfilled according to Koch's postulate. The identification of the pathogen was carried out according to the morphological and cultural characteristics and rDNA-ITS sequence analysis. The effects of culture medium, temperature, pH value, carbon and nitrogen sources, and light on mycelium growth and sclerotia production of the pathogen were studied. The mycelium growth rate was used to test the susceptibility of pathogen for 14 fungicides. Results: The M. dauricum target spot was caused by Streptobotrys caulophylli. The optimal medium for mycelium growth was PDA; PDA and PSA media were suitable for the sclerotium production. The optimal temperature ranges for mycelium growth and spore production were 20-28℃ and 10-30℃ and were suitable for sclerotium production. The suitable pH values for mycelium growth and sclerotium production were 4-9 and 5-11, respectively. Sucrose and L-glutamine were the optimal carbon and nitrogen sources for mycelium growth. Synanthrin and sucrose were the optimal carbon source and sodium nitrate was nitrogen source for sclerotium production. The total light could promote mycelium growth, while the darkness could promote sclerotium production. The pathogen was sensitive to procymidone, cyprodinil, iprodione, fludioxonil, metalaxyl•mancozeb, and pyraclostrobin•metiram with EC50 < 1.0 mg/L and EC90 < 5.0 mg/L. Conclusion: It is the first report on M. dauricum target spot caused by S. caulophylli in China. The suitable conditions (culture medium, temperature, pH value, carbon and nitrogen sources, and light) for mycilium growth and sclerotium production are determined. The above six fungicides are screened as further field trial agents for disease control.