关键词: 八棱海棠腐烂病, 病原鉴定, Valsa mali, 生物学特性, 毒力测定

Abstract: By using Malus×robusta（CarriŠre）Rehd as the test material，the pathogenic fungi were isolated using tissue isolation method，and their pathogenicity was determined according to Koch’s postulates.The morphological characteristics of the pathogenic fungi and rDNA⁃ITS sequence analysis were combined to identify the types of pathogenic fungi，their biological characteristics were investigated，and through indoor toxicity tests，the most virulent chemical fungicides were selected against the pathogenic fungi of Malus×robusta rot disease，in order to provide reference basis for the comprehensive prevention and control of Malus×robusta rot disease. The results showed that the two strains of pathogenic fungi HL⁃23 and HL⁃100 isolated from Malus×robusta suffering from canker were both Valsa mali.The biological characteristics of strains HL⁃23 and HL⁃100 were analyzed by measuring the colony diameter via the cross⁃method.The results showed that strains HL⁃23 and HL⁃100 were most suitable for cultivation on PDA medium.The optimal pH value for mycelial growth was 5.0，and the optimal temperature was 25—30 ℃.They were suitable for growth under 12 hours of light and dark alternation conditions，the optimal carbon source was sucrose，and the most suitable nitrogen source was ammonium dihydrogen phosphate.The toxicity of nine commonly used chemical fungicides，such as difenoconazole and azoxystrobin，against the pathogenic fungi HL⁃23 and HL⁃100 of Malus×robusta rot disease was determined through indoor plate experiments. It was found that the inhibition rates of nine fungicides on the same type of fungal strains HL⁃23 and HL⁃100 were significantly different.The best inhibition effect was difenoconazole，with EC₅₀ values of 0.010 9—0.0110 mg/L；The second was azoxystrobin，with EC₅₀ values of 0.015 8—0.018 1 mg/L.

Key words: Malus×robusta rot disease, Pathogen identification, Valsa mali, Biological characteristics, Toxicity test