朝鲜蓟细菌性根茎腐烂病病原的分离与鉴定

 在湖南省常德市西洞庭管区种植的朝鲜蓟（Cynara scolumus  L.）上发现了一种新的病害，其症状表现为地上部分从外层叶片开始逐步枯萎，随后根部和主茎杆的髓部腐烂变褐，最后整株枯萎。从田间感病朝鲜蓟茎杆的病健交界处用NA培养基分离，获得10个菌株，分别指定为HNXDT001~010，并进行了致病性测定、形态观察和细菌学特征分析，同时对HNXDT002菌株进行分子生物学鉴定。结果表明，该系列菌株在NA培养基上均形成灰白色圆形菌落，稍突起，有光泽，半透明。在显微镜下菌体呈短杆状，两端钝圆，具有2～8根周生鞭毛，革兰氏阴性。10个菌株通过针刺法接种均可导致朝鲜蓟茎杆、胡萝卜、辣椒、白菜、土豆、番茄和莴苣茎杆软腐，经科赫法则验证为致病病原菌。该菌株的16S rDNA序列和果胶酶基因片段测序(分别用16S rDNA通用引物16SF/16SR和果胶酶基因引物Y1/Y2扩增)与系统发育学分析表明，其16S rDNA序列(GenBank Accession No. JF721958)与胡萝卜软腐果胶杆菌胡萝卜亚种（Pectobacterium carotovorum  subsp.  carotovorum）菌株ATCC15713 (GenBank Accession No. U80197)序列同源性高达99％;果胶酶基因序列(GenBank Accession No. JF721960)与胡萝卜软腐果胶杆菌胡萝卜亚种（Pectobacterium carotovorum subsp. carotovorum）PC1菌株(GenBank Accession No. CP001657)序列同源性为93%。结果表明：朝鲜蓟细菌性根茎腐烂病病原为胡萝卜软腐果胶杆菌胡萝卜亚种。

Isolation and identification of bacterial pathogen causing stem and root rot on artichoke

A new disease on globe artichoke(Cynara scolymus L.) was observed in commercial fields in Changde,Hunan Province,China.Typical symptoms were wilting and necrosis from the outermost leaves,dark brown discoloration of the vascular tissue and pith of main stem.Eventually,the plants wilted and died.Manual weeding and cuttings often led to the development of typical soft rot during propagation.To investigate the causal agent of the disease,isolations were made from rotted stems of field artichoke plants on nutrient agar(NA).Bacteria consistently isolated from the diseased tissues formed grey-white,glossy,convex,translucent,and round colonies on NA.The bacterial cells were gram-negative rods with 2 to 8 peritrichous flagella and rounded ends under the microscope.In artificial inoculation test,these isolates could also cause stem rot of Chinese cabbage,pepper,lettuce and artichoke,and slice rot of carrot,tomato and potato within 48 h at 28℃.The results demonstrated that these isolates are causative agent of soft-rot disease.PCR amplification was carried out by utilizing universal 16S rDNA primer pair 16SF/16SR and pel gene primers Y1/Y2.The 16S rDNA and pel gene sequences of isolate HNXDT002(GenBank accessions JF721958 and JF721960,respectively) had 99% and 93% nucleotide identity with strains of Pectobacterium carotovorum subsp.carotovorum(GenBank accessions U80197 and CP001657,respectively).It came to the conclusion that the causal agent of soft-rot disease on artichoke belonged to Pectobacterium carotovorum subsp.carotovorum.