莲雾灰斑病病原菌鉴定及室内药剂筛选

Pathogen identification and fungicides screening for grey spot of Syzygium samarangense

为了探明莲雾灰斑病病原菌和对该病有效的杀菌剂种类,采用组织分离法进行病原菌分离,同时借助形态学特征和ITS序列进行鉴定,测定了病原菌菌丝生长的最适环境和碳氮营养条件,并进行室内药剂筛选。结果表明,莲雾灰斑病病原菌菌丝白色绒毛状,产孢结构为分生孢子盘,分生孢子梗无色瓶状,分生孢子单胞无色,椭圆形至长椭圆形,大小(13.2~23.16)μm×(4.8~7.5)μm,ITS序列长为553 bp,系统进化发现该菌与胶胞炭疽菌(Colletotrichum gloeosporioides)归为一支。该菌在25~30℃生长较快,中性和偏碱条件适宜菌丝生长,最适碳氮源分别为蔗糖和蛋白胨。5种杀菌剂对莲雾灰斑病病原菌具有较强的抑制效果,按其毒力高低排序:250 g/L丙环唑乳油(EC_(50)为0.003 mg/L)>250g/L吡唑醚菌酯乳油(EC_(50)为0.264 mg/L)>75%肟菌酯戊唑醇水分散剂(EC_(50)为0.610 mg/L)>50%戊唑嘧菌酯悬浮剂(EC_(50)为0.834 mg/L)>37%苯醚甲环唑水分散剂(EC_(50)为2.370 mg/L)。因此,莲雾灰斑病的病原为胶胞炭疽菌(Colletotrichum gloeosporioides),适生性较强,250 g/L丙环唑乳油和250 g/L吡唑醚菌酯悬浮剂可作为田间防治该病害的候选药剂种类。

In this investigation,the pathogen of the gray spot of Syzygium samarangense was isolated with tissue separation method,and identified by morphological characteristics and ITS sequence.The optimum culture condition for the growth of pathogen hyphae was determined and the effective fungicides against it were screened.The results showed that the colony of the pathogen was white and fluffy,the sporulation structure was acervulus,and the conidiophore was colorless and bottle-shaped.The conidium was single-celled,colorless,elliptic or long oval,with the size of (13.2~23.16)×(4.8~7.5)μm.The length of the ITS segment was 553 bp,and this pathogen was clustered into the clade of Colletotrichum gloeosporioides by phylogenetic analysis of ITS.The colony of the pathogen grew fast at 25~30℃,and a neutral or slightly alkaline pH was preferred.The most suitable carbon and nitrogen source for mycelium growth was sucrose and peptone,respectively.The inhibition effects of five fungicides on the pathogen were as follow:250 g/L propiconazole EC (EC_(50)0.003 mg/L)>250 g/L pyraclostrobin EC (EC_(50)0.264 mg/L)>75%trifloxystrobin tebuconazole WG (EC_(50)0.610mg/L)>50%azoxystrobin WG (EC_(50)0.834 mg/L)>37%difenoconazole SC (EC_(50)2.370 mg/L).The pathogen of the gray spot of Syzygium samarangense showed strong adaptability towards different culture conditions and was identified as Colletotrichum gloeosporioides.It is recommended to choose 250 g/L propiconazole EC and 250 g/L pyraclostrobin EC for gray spot control in the field.