Identification and Characterization of Causal Agent of Sweet Osmanthus Leaf Blight in Guangxi

A sweet osmanthus leaf blight severely occurred in Nanning city,Guangxi,China.The pathogen was isolated and its pathogenicity to sweet osmanthus plants confirmed by inoculation tests.The pathogenic isolate CHS was identified as Alternaria alternata(Fr.)Keissler based on its morphological characteristics and ITS sequence.The optimum temperature and pH value for growth and conidial germination were 28 ℃ and 6-7,respectively.Different conditions of light showed no obvious effect on the mycelial growth.Black light was favorable for conidial production.Tests on fungicidal sensitivity in vitro showed that the pathogen was highly sensitive to difenoconazole,prochloraz and propiconazole.This is the first record of sweet osmanthus leaf blight caused by A.alternata in Guangxi.