芝麻细菌性青枯病病原菌及其生化变种鉴定

芝麻细菌性青枯病是我国南方芝麻生产上的重要病害。调查研究表明,芝麻青枯病除前人报道的萎蔫、顶梢常有溃疡裂缝等典型症状外,还有植株畸形、茎秆表皮泡状突起、溃疡裂缝延伸至茎秆中下部、折断茎秆可见菌脓形成的透明细丝等症状。分离获得的病原菌菌株经菌体形态、菌落形态、培养性状、致病性、烟草过敏性反应及16S rRNA基因和16S～23S rRNA基因间区ITS序列测定,证实了芝麻青枯病是由青枯菌Ralstonia solanacearum引起。江西省15个县(市)的22个代表性菌株的生化变种鉴定显示,20株菌属于生化变种Ⅲ,占90.91%,2株属于生化变种Ⅳ,占9.09%。说明生化变种Ⅲ菌群是诱发芝麻青枯病流行的优势种群。

Identification of the pathogen causing bacterial wilt of sesame and its biovars

Bacterial wilt is one of the most serious diseases of sesame in south China.This disease usually severely reduces the yield of sesame.Besides usual typical symptoms of overwilt,gap on the top part of stem,there had symptoms of sesame wilt,including deformation,alveolar bulge with bacterial ooze on stem,gap on the lower part of stem,filiform bacterial ooze in broken stem appeared in the 2-year field studies.The strains isolated from the sample of sesame bacterial wilt were identified as Ralstonia solanacearum based on their morphology,cultural characteristics,pathogenicity test and tobacco anaphylaxis.The sequence analyses of 16S rRNA gene and 16S-23S rRNA gene ITS demonstrated 99%-100% similarity to R.solanacearum.Biovar test of 22 isolates which collected from 15 counties in Jiangxi Province showed that 20 strains belong to biovar Ⅲ,and 2 strans belong to biovar Ⅳ,accounted for 90.91% and 9.09% of the 22 isolates,respectively.It means that biovar Ⅲ is a dominant pathogen induced sesame bacterial wilt epidemics.