Identification of the pathogen causing Begonia×benariensis anthracnose, detection of the biological characteristics and indoor toxicity determination of control fungicides

【Objective】 To clarify the pathogenic species of Begonia×benariensis anthracnose and its biological characteristics,to screen out the fungicides suitable for the control of this disease,which could lay the foundation for the re‐search on the occurrence and development regulation of Begonia×benariensis anthracnose as well as the control measures.【Method】Pathogenic fungi were isolated from Begonia×benariensis plants showing typical anthracnose symptoms col‐lected from the Kunming World Horticultural Expo Garden in Yunnan using the tissue isolation method.The pathogenicity of the isolated strains was confirmed according to Koch’s law.The taxonomic identity of the anthracnose pathogen was de‐termined by combining morphological observations with a multigene analysis of ITS,TUB2,HIS3,CHS-1,GAPDH and .The biological characteristics of the pathogen were investigated by examining mycelial lethal temperature and myce‐lial growth under different conditions,including various culture media,carbon sources,nitrogen sources,temperatures,illumination periods and p H levels.The inhibitory effects of 8 fungicides on the growth of the pathogen colony were as‐sessed using mycelial growth rate method. 【Result】 Thirteen strains were isolated and purified from the pathogenic plants of Begonia×benariensis,and the thirteen strains were categorized as the same species according to colony morphology and microscopic morphology,and the representative strain SWBG5 was selected for the subsequent experiments.According to morphological observations combined with multigene phylogenetic tree,the anthracnose pathogen SWBG5 was identified as Colletotrichum aotearoa.Biological experiments showed that PDA medium was beneficial for the growth of SWBG5 strain,with the fastest mycelial growth occurring when peptone was used as the nitrogen source,soluble starch as the carbon source,and at a temperature of 25℃.The mycelia of strain SWBG5 could grow well under 24 h light or 24 h darkness.The optimal p H was found to be 6,and the lethal temperature was 54℃.Indoor fungicide toxicity tests re‐vealed that all the 8 fungicides inhibited the mycelial growth of strain SWBG5,with 30%pyraclostrobin SC exhibiting the strongest inhibitory effect,with an inhibitory concentration (EC₅₀) value of 1.6959μg/m L. 【Conclusion】 The patho‐gen of anthracnose of Begonia×benariensis in the Kunming World Horticultural Expo Park in Yunnan is Colletotrichum aotearoa,and 30%pyrazoxystrobin can be recommended for controlling this disease in future treatment.