| Sclerotinia stem rot caused by Sclerotinia sclerotiorum is the primary disease of rape,the pathogen has a broad host range and worldwide distribution. Shaanxi is one of theplanting areas of China’s winter oilseed rape, the incidence of stem rot occurs morecommonly in the central and southern of Shaanxi and it has a serious impact on the qualityand yield of oilseed rape. So far, the genetic evolution and genetic diversity of S. sclerotiorumin Shaanxi is not yet clear, which causes a restriction to the understanding of the diseaseepidemic regularigy, as well as the prevention and control methods.The genetic diversity of144S. sclerotiorum strains from different regions in Shaanxiand15S. sclerotiorum strains from different hosts was studied by SRAP and ISJ markers, ofwhich the results obtained were as followed:1PCR amplified system of S. sclerotiorum based on SRAP markers was set up and wasused to analysis the genetic diversity of the tested strains. Nine primer pairs were screenedfrom150SRAP primer combinations based on their good polymorphism and stableamplification.76polymorphic bands were produced by the amplification of144isolates,which was88.4%of the total bands, and the similarity coefficient was from0.361to0.936.Meanwhile, with the amplification of18strains from different hosts, we got62polymorphism bands which made up84.9%of the band’s total, and the similarity coefficientwas from0.358to0.976. The UPGMA (Unweighted Pair Group Method with ArithmeticMean) cluster analysis showed that the dendrogram consisted of four groups when the geneticsimilarity coefficient of144strains in different regions was0.658. Group I consisted ofcounties mainly in Hanzhong, while Group IV consisted of2counties in Ankang. Group IIand III are groups from mixed regions. Meanwhile, the dendrogram consisted of three groupswhen the genetic similarity coefficient of18strains in different hosts was0.788, and83.3%of them were in group I consisting of all host types. The dendrogram consisted of threegroups when the genetic similarity coefficient of38strains of different pathogenicity was0.730. They are relatively weak pathogenicity isolates in group A, combined pathogenicity inB and C. Results showed a rich SRAP polymorphism among the population of S.sclerotiorum in Shaanxi and had certain relationship with genetic diversity and geographicallocation, however, no significant correlation existed generally, nor did the isolates in different host origin and pathogenicity.2PCR amplified system of S. sclerotiorum based on ISJ markers was set up and wasused to analysis the genetic diversity of the tested strains. In this study, eight primer pairsscreening from14ISJ primer combinations were used to amplify isolates from differentregions and different hosts, it also received high polymorphism ratio, respectively,73.1%,89.4%. The UPGMA (Unweighted Pair Group Method with Arithmetic Mean) clusteranalysis showed that the dendrogram consisted of two groups when the genetic similaritycoefficient of144strains in different regions was0.646. Both groups were mixed groups,while Group I accounted for72.9%of the total number, Group Ⅱ was made up by a smallnumber of strains. Meanwhile, the dendrogram consisted of three groups when the geneticsimilarity coefficient of18strains in different hosts was0.760, and83.3%of them were ingroup I consisting of all host types. The dendrogram consisted of two groups when thegenetic similarity coefficient of36strains of different pathogenicity was0.650. Each groupcontained strains with different virulence levels. Results showed a rich ISJ polymorphismamong the population of S. sclerotiorum in Shaanxi, but had no significant correlation withgenetic diversity and geographical location, nor did the isolates in different host origin andpathogenicity.3SRAP analysis results and the ISJ analysis results are basically the same, indicatingthat both of them can be used for the analysis of the genetic diversity of S. sclerotiorum, andits results are stable and reliable. |
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