脆红李叶斑病病原菌的鉴定及抑菌药剂的筛选

Identification of the pathogen causing leaf spot of Prunus salicinaand screening of fungicides

为明确脆红李叶斑病的病原菌,采用组织分离法分离纯化病原菌,通过形态学特征结合多基因联合序列分析鉴定病原菌;采用孢子喷洒法和针刺接种法测试其致病性。结果表明:从脆红李叶斑病病叶分离得到4株形态一致的真菌菌株,其代表菌株LY12的菌落呈圆形,菌丝白色至浅黄色;分生孢子器球形,黑色;分生孢子无色,单孢,多为椭圆形;采用ITS、TUB2和LSU 3段基因联合构建系统发育树,菌株LY12与荸荠茎点霉(Didymella bellidis)聚为一支;根据形态学特征和系统发育分析,确定LY12为荸荠茎点霉(Didymella bellidis);致病力测试发现,该病原菌可以侵染川渝地区青脆李、半边红、青柰、金脆李和脆红李的叶片、枝条和果实,叶片受害最严重,也可侵染尤力克柠檬、爱媛38杂柑、塔罗科血橙3个柑橘品种的叶片和果实;室内药剂筛选结果表明,24种杀菌剂中,50%啶酰菌胺水分散粒剂、38%唑醚·啶酰菌胺悬浮剂、25%嘧菌酯悬浮剂、75%肟菌·戊唑醇水分散粒剂等11种杀菌剂对病原菌菌丝生长有较强的抑制作用,病原菌对50%啶酰菌胺水分散粒剂最敏感,EC50为0.1531µg/mL。

In order to clarify the pathogen causing the leaf spots of Prunus salicina,tissue isolation was performed to isolate and purify the pathogen,which was further identified by morphological characteristics and polygenic joint sequence analysis.The pathogenicity of the pathogen was determined by spore spraying method and acupuncture inoculation method,and 24 fungicides were screened indoors.The results showed that 4 fungal strains with the same morphological characteristics were isolated from the diseased Prunus salicina leaves.The representative strain LY12 had round colonies and white to light yellow hyphae;and had spherical,black pycnidium,with conidia colorless,monospore,mostly oval.The genes of ITS,TUB2 and LSU were used to construct the phylogenetic tree.The results showed that strain LY12 and Didymella bellidis were clustered in the same branch.According to morphological characteristics and phylogenetic analysis,strain LY12 was identified as Didymella bellidis.The pathogenicity test showed that the pathogen strain LY12 could infect the leaves,branches and fruits of plum varieties in Sichuan and Chongqing,including Qingcuili,Banbianhong,Qingnai,Jincuili,and Cuihongli,and the largest lesions appeared on the leaves.The pathogen could also infect leaves and fruits of citrus varieties including Ulick lemon,Ehime 38,and Taroko blood orange.Indoor fungicides screening test showed out of the 24 fungicides,11 kinds of fungicides,such as 50%boscalid water dispersible granule,38%boscalid·pyraclostrobin suspending agent,25%azoxystrobin suspension,75%trifloxystrobin·tebuconazole water dispersible granule ect.,showed strong inhibitory effect on pathogen strain LY12.And 50%boscalid water dispersible granule had the most obvious inhibitory effect,with EC50 being 0.1531µg/mL.