Phylotype and sequevar determination and AFLP fingerprinting of Ralstonia solanacearum strains causing bacterial wilt of potato in southeastern Iran

摘要

Bacterial wilt of potato caused by Ralstonia solanacearum is a severe threat to potato cultivation in Kerman province, located in southeastern Iran and the third largest potato producer in the country. The present study intends to determine the precise phylogenetic position, sequevar, and genetic diversity of R. solanacearum strains associated with the disease. To this end, the major potato-growing regions of the province (Jiroft and Laleh Zaar) were surveyed to collect tuber samples from affected potato plants showing typical wilt symptoms. Twenty-three strains were collectively purified and subjected to phenotypic and genotypic characterization. Biochemical tests showed that all the strains belonged to R. solanacearum biovar 2A. Furthermore, phylotype-specific multiplex polymerase chain reaction results indicated that the strains belonged to phylotype II. For sequevar typing as well as the determination of the phylotype subcluster (IIA/IIB), polymerase chain reaction amplicons of the endoglucanase precursor gene of 11 representative strains were sequenced. In phylogenetic analysis, the strains were grouped with the reference strains of phylotype IIB-1 retrieved from the GenBank. Then, to assess genetic diversity, 19 selected strains were subjected to genomic fingerprinting, i.e., amplified fragment length polymorphism (AFLP) using seven primer pair combinations. The AFLP data showed heterogeneity among the strains of R. solanacearum and were grouped into four clusters. With our knowledge, this is the first report of the phylotype, and sequevar determination (i.e., IIB-1) in addition to AFLP-based genomic fingerprinting of R. solanaceraum strains causing potato wilt in southeastern Iran.