The pectinolytic species Pseudomonas viridiflava has a wide host range among plants, causing foliar and stem necrotic lesions and basal stem and root rots. However, little is known about the molecular evolution of this species. In this study we investigated the intraspecies genetic variation of P. viridiflava amongst local (Cretan), as well as international isolates of the pathogen. The genetic and phenotypic variability were investigated by molecular fingerprinting (rep-PCR) and partial sequencing of three housekeeping genes (gyrB, rpoD and rpoB), and by biochemical and pathogenicity profiling. The biochemical tests and pathogenicity profiling did not reveal any variability among the isolates studied. However, the molecular fingerprinting patterns and housekeeping gene sequences clearly differentiated them. In a broader phylogenetic comparison of housekeeping gene sequences deposited in GenBank, significant genetic variability at the molecular level was found between isolates of P. viridiflava originated from different host species as well as among isolates from the same host. Our results provide a basis for more comprehensive understanding of the biology, sources and shifts in genetic diversity and evolution of P. viridiflava populations and should support the development of molecular identification tools and epidemiological studies in diseases caused by this species.
Bacterial isolates from tomato plants with symptoms revealing pith necrosis collected over a 20‐year period were screened and characterized using biochemical and pathogenicity tests, as well as molecular approaches. The examined isolates were categorized into two main Pseudomonas species: P. corrugata and P. mediterranea. The diversity of these isolates was characterized through a variety of biochemical, serological, pathogenicity, DNA fingerprinting and multi‐locus sequence analysis features. Of the total Pseudomonas isolates causing pith necrosis, the biochemical profile of the selected non‐fluorescent pseudomonads consisting of P. corrugata and P. mediterranea revealed differentiation in only three characters among 43 examined. Serological analysis managed to identify the P. corrugata isolates using the laboratory prepared antiserum anti‐PC14. Genomic analyses using rep‐PCR fingerprinting and multilocus sequence analysis (MLSA) revealed considerable inter‐ and intraspecies genetic diversity. However, artificial inoculations of several plant species revealed similar pathogenicity patterns for both P. corrugata and P. mediterranea isolates. These results provide the basis for a more comprehensive understanding of the biology, sources and shift in genetic diversity and evolution of both P. corrugata and P. mediterranea populations and could support the development of molecular identification tools and epidemiological studies in diseases caused by these species. Moreover, this is the first report of P. mediterranea in Greece on tomato as well as on pepper plants.
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