Pathogenicity Variation And Host Specificity Testing Of Ralstonia Solanacearum From Pogostemon Cablin(Blanco) Benth

In this study,pathogenies of bacterial wilt disease from infected Pogostemon cablin plants were isolated using streak plate method.And they were identified by typical colonies of Ralstonia solanacearum on TTC medium and inoculation as a pathogenicity test.Further identification of the isolates were conducted by PCR using the specific primers OLI1/Y2 of R.solanacearum.The results confirmed that strain HX6,strain PC10,strain PC30 and strain PC50 were R.solanacearum.Pathogenicity tests on P.cablin plants were performed for the R.solanacearum strains.Host specificity tests of R.solanacearum strains were performed on different hosts including P.cablin,tomato and peanut by detached-leaf inoculation and seedlings inoculation.The research help to further understand diversity and host range variation of R.solanacearum strains from P.cablin and might develop the integrated management strategies for bacterial wilt.1 Review on relevant literatures in domestic and abroadThe general situation of present studies on Pogostemon cablin and identification methods of Ralstonia solanacearum were summarized on the basis of previous work in domestic and abroad.And the progress of pathogen host specificity was introduced.2 Isolation of pathogenies of bacterial wilt disease from infected Pogostemon cablin plants and their identification by PCRPathogenies of bacterial wilt disease from infected Pogostemon cablin plants were isolated using streak plate method.And they were identified by typical colonies of Ralstonia solanacearum on TTC medium and inoculation as a pathogenicity test.Further identification of the isolates were performed by PCR using the specific primers OLI1/Y2 of R.solanacearum.PCR result showed that strain HX6(isolated in a previous work),strain PC10,strain PC30 and strain PC50 produced the expected PCR product.The results confirmed that strain HX6,strain PC10,strain PC30 and strain PC50 were R.solanacearum.3 Test for variation in pathogenicity of Ralstonia solanacearum strainsPathogenicity testing for Ralstonia solanacearum strain HX6 in varied growth phases indicated the virulence became strong with the extending growth period,and maintained steady levels after reaching specific range.The pathogenic virulence in the lag phase was relatively weak,while became apparently stronger in the later logarithmic phase.The results for different concentration assay proved that higher bacterial concentration resulted in stronger pathogenicity.Otherwise pathogenicities of different R.solanacearum strains were not the same.The disease indexes for plants infected with strain PC50 and strain HX6 were approximately 100 post 6-days inoculation.The results indicated that pathogenicities of both strains of PC50 and HX6 were strong,followed by strain PC10.While strain GIM1.7 displayed the weakest pathogenicity among the strains.This study revealed that there is pathogenicity variation among R.solanacearum strains.4 Host specificity testing of Ralstonia solanacearum strainsHost specificity tests of Ralstonia solanacearum strains were performed on different hosts including Pogostemon cablin,tomato and peanut by detached-leaf inoculation and seedlings inoculation.The results showed that strain PC10,strain PC30 and strain PC50 were more virulent to P.cablin than tomato and peanut.While strain GIM1.7 showed a weak pathogenicity to P.cablin.The results above suggest that R.solanacearum strains have race-cultivar specificity on plant hosts.