Identification,Detection And Bactericide Screening Of Pathogen Causing Kiwifruit Bacterial Canker In Fengxin County

Kiwifruit bacterial canker is one of the most serious diseases endangering the development of kiwifruit industry in the world.Since 2008,the disease has occurred in Fengxin county,Jiangxi province.In recent years,the disease has become more serious,even resulting in destruction of the whole orchard.In order to fully understand the pathogenic species of kiwifruit bacterial canker in Fengxin county and lay a foundation for prevention and follow-up studies of the disease,a series of studies of pathogenic identification,population structure,rapid detection technology,and screening of indoor chemical agents on the disease were carried out by means of traditional biology and molecular biology,and the pathogen of summer canker disease of kiwifruit was identified.All result were reported as follows:1)A total of 29 samples of kiwifruit bacterial canker were collected from 7 orchards in Fengxin county.The pathogenic bacteria were isolated from the samples by dilution method and their pathogenicity was tested,and 27 pathogenic bacterial strains were obtained.The culture traits and morphological observations,physiological and biochemical tests and rDNA sequences were performed on these strains.Based on the results,the pathogen of kiwifruit bacterial canker in Fengxi county was identified as Pseudomonas syringae pv.actinidiae.2)By using the multilocus sequence analysis?MLSA?method,the six housekeeping genes acnB,cts,gapA,gyrB,pfk and rpoD of the kiwifruit canker bacteria isolated from Fengxin county were used as target genes for MLSA typing.The results showed that all the isolates from Fengxin county were biovar 3.Subsequently,the reliability of the results was further verified using specific primers of the pathogen biotype.3)Seven pairs of specific primers at home and abroad were used to amplify DNA of kiwifruit bacterial canker pathogen in Fengxin county,and the sensitivity of specific primers was analyzed,and then the field sample detection was carried out with high specificity and sensitivity.The results showed that the nested PCR system with B1/B2 and KNF/KNR primers can be applied to the field sample detection of kiwifruit bacterial cankers in Fengxin county.4)The indoor virulence of 29 fungicides against kiwifruit bacterial canker was determined by Oxford Cup method.The results showed that the bacteriostasis effect of different fungicides to kiwifruit bacterial canker pathogen was significantly different.Tetracycline?0.3%?and bromonitrol?20%?had the best bacteriostatic effect with EC₅₀0 of0.002mg/L and 0.068mg/L,respectively;The EC₅₀0 of allicin?80%?and thiamethone?1.5%?was the second,and its EC₅₀0 is 7.104mg/L,19.974mg/L,respectively,Thirdly,9 fungicides,including bacteriobiotics?3%?,chloromycin?2%?,agricultural streptomycin?72%?,mancozeb?80%?,cupric tyrosine?15%?,chloro-bromo-isocyanuric acid?50%?,cupric wang?47%?,basic copper sulfate?27.12%?,and copper hydroxide?46.1%?gradually decreased.There were no bacteriostatic effects on pathogen with 16 agents,such as suxiongjiao copper?30%?,mesophytic zinc thiazole?20%?,quinoline copper?80%?and ningnanmycin?1.5%?.5)During the research period of this paper,a bacterial canker-like symptoms on yellow kiwifruit?Actinidia chinensis cv.Hort16A?were observed in Fengxin county of Jiangxi province,which was tentatively named as kiwifruit summer canker.Through the analysis of culture traits,morphological characteristics,physiological and biochemical tests,pathogenicity determination,combined with 16s rDNA,carA,atpD,recA,and specific carA fragments of 20 strains isolated,the pathogen of kiwifruit summer canker in Fengxi county was identified as Pectobacterium carotovorum subsp.actinidiae.