口红吊兰菌核病病原鉴定及其生物学特性分析
Identification and characterization of the pathogen of Sclerotinia rot of Aeschynanthus pulche

为鉴定1株分离自口红吊兰叶部病斑上的疑似核盘菌菌株，利用柯赫氏法则验证其致病性并通过形态观察和ITS序列分析对该病原菌进行分类鉴定，结合温度、酸碱度等生理指标研究其生物学特性，并利用菌丝生长速率法测定了扑海因、多菌灵、苯醚甲环唑、腐霉利4种药剂对该病原菌的抑制作用。结果显示：在PDA平板上该病原菌菌丝为白色，均匀生长；约7 d后开始产生菌核，直径3～5 mm；菌核萌发后可产生1～3个子囊盘，内含8个大小为8.0～12.0μm×4.0～5.5μm的子囊孢子。该菌株ITS序列系统进化分析结果显示，其与核盘菌的同源性高达99%。综上所述，初步确定该菌株为核盘菌Sclerotinia sclerotiorum。该病原菌在PDA培养基上的最适生长温度为20～25℃、最适生长pH为5～7。室内毒力测定发现供试4种药剂中扑海因对该病原菌菌丝生长有较好的抑制效果，且其EC50最小，仅为0.62 mg/L，证明扑海因对核盘菌毒力最强。
In order to identify the fungal isolate obtained from disease lesions on leaves of Aeschynanthus pulche, experiments were performed including pathogenicity test, morphology and ITS sequence analysis. Physiological properties of the fungus including the temperature and pH optimal for growth were investigated; effects of four commonly used fungicides (iprodione, carbendazim, difenoconazole and procymidone) on the growth of mycelium were also evaluated. The fungal mycelium was white and grew homogeneously on PDA plate, and sclerotia of 3-5 mm in size were observed to form in about 7 days. Sclerotia were able to germinate and to produce 1-3 apothecia bearing asci that contain eight ascospores 8.0-12.0 μm×4.0-5.5 μm in size. The analysis of ITS rDNA sequences showed that the fungus shared the highest homology (up to 99%) with Sclerotinia sclerotiorum. Based on the above results, the fungus was identified as S. sclerotiorum. The temperature and pH optimal for mycelium growth on PDA plate were 20-25℃ and 5-7, respectively. Indoor evaluation tests showed that iprodione had the greatest inhibitory effect on hyphal growth among four tested fungicides with the lowest EC50 of 0.62 mg/L.