Pathogen Identification Of Artichoke Stem And Root Rot And In Vitro Bioassay

Artichoke was a kind of Characteristics of crops in winter with high economic value, the net income of planting artichokes up to12,000RMB/hm2in Changde, Hunan Province, China. the promotion of artichokes and other crops companion planting, can greatly improve agricultural efficiency. A new disease on globe artichoke (Cynara scolymus L.) was observed in the spring of2008and2009, and both the spring and fall seasons of2010in commercial fields (nearly1,000ha) Characteristic symptoms were wilting and necrosis of the outermost leaves, and dark brown discoloration of the vascular tissue and pith of the stem base. Eventually, the plant wilted and died. Manual weeding and cuttings often developed a typical soft rot during propagating.Nearly5%,35%, and4%(2008,2009, and2010, respectively) of the artichoke fields were destroyed because of the disease.To investigate the causal agent of the disease, isolations were made from rotted stems of field artichoke plants on nutrient agar,40strains were obtained, named HNXDT01-40.HNXDT02, HNXDT12and HNXDT30were all fulfiled Koch's postulates. The three isolates could also cause soft rot of carrot, potato slice, lettuce stem,Chinese cabbage stem, pepper, tomato and cucumber fruits within48h at28℃in artificial inoculation test.Pathogens HNXDT02,HNXDT12and HNXDT30were further characterized based on the traditional morphological and molecular biological methods. Isolates HNXDT02,HNXDT12and HNXDT30were Gram negative and rod-Shaped, with a peritrichous flagella arrangement。They formed grey-white, glossy, convex, translucency, and round colonies on NA. The bacterial cells were gram-negative rods with2to8peritrichous flagella under microscope.The major fatty acid composition of the three pathogens were C12:0,C14:0, C16:0and C18:1w7c.Pathogens HNXDT02,HNXDT12and HNXDT30were classified at the subspecies level of Pectobacterium carotovorum subsp. carotovorum by GC-FAME analysis systems, similar index were94.5%,95.7%å'Œ88.5%, respectively.PCR amplification was carried out by utilizing universal16S rDNA primer pair16SF/16SR and pel gene primers Y1/Y2. The16S rDNA and pel gene sequences of isolate HNXDT02(GenBank accessions JF721958and JF721960, respectively) had99%and93%nucleotide identity with a strains of P. carotovorum subsp. carotovorum (GenBank accessions U80197and CP001657, respectively). It comes to the conclution that the causing agent of soft-rot disease on artichoke belongs to Pectobacterium carotovorum subsp. carotovorum.Bioassay was carried out to screen effective inhibiting agents of the disease. Out of tested antibiotics, streptomycin, Gentamicin, Amikacin and Tetracycline showed the highest inhibitory effect to the pathogen with potential disease control in practice. In an in vitro inhibition test against isolates HNXDT02,HNXDT12and HNXDT30, strain DC53out of354tested actinomycetes strains showed best antagonistic activity, which gave a possible biological control tool.