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Who’s who : Resolving the taxonomy of the causal agent of bacterial leaf spot of lettuce through a polyphasic approach leads to combine Xanthomonas hortorum Vauterin et al. 1995 and Xanthomonas cynarae (Trébaol 2000) Timilsina et al. 2018

Abstract : Assessment of the taxonomy and diversity of the Xanthomonas strains causing bacterial leaf spot of lettuce (BLSL), commonly referred as Xanthomonas campestris pathovar vitians, has been a long-lasting issue which held back the global efforts made to understand this disease and struggle against the damages it causes in the field. In order to restore sane bases essential to the study of this pathogen, we conducted an extensive polyphasic approach on a panel of strains obtained through sampling campaigns or collection strains acquisitions. Results of a multilocus sequence analysis crossed with pathogenicity assays revealed that BLSL-causing strains formed a monophyletic pathovar sparsely diversified in three clonal groups. However, genome-based phylogenies yielded only two major groups of strains. From the bigger picture perspective, phylogenies exhibited the intermediate position of pathovar vitians between close species X. hortorum and X. cynarae, resulting in a phylogenetic continuum regarding the known diversity of the genus. Finally, whole-genome comparisons of all type, pathotype or representative strains of these two species by multiple overall genome relatedness indices (OGRIs) calculation endorsed the hypothesis of one single specie. Carbon and nitrogen sources utilization tested using Biolog microplates did not revealed any particular phenotypic differences which would have legitimate the distinction into two species. Therefore, we propose the combination of X. hortorum, X. cynarae and X. campestris pv. vitians into a new X. hortorum comb. nov. with CFBP 4925 T = LMG 937 T remaining the type strain, and LMG 938 neoPT = NCPB 2248 neoPT becoming the pathotype strain of X. hortorum pv. vitians.
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https://hal-univ-lyon1.archives-ouvertes.fr/hal-02561964
Contributor : Lucas Morinière <>
Submitted on : Monday, May 4, 2020 - 11:37:53 AM
Last modification on : Monday, July 6, 2020 - 3:40:09 PM

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  • HAL Id : hal-02561964, version 1

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Lucas Morinière, Alexandre Burlet, Emma Rosenthal, Xavier Nesme, Perrine Portier, et al.. Who’s who : Resolving the taxonomy of the causal agent of bacterial leaf spot of lettuce through a polyphasic approach leads to combine Xanthomonas hortorum Vauterin et al. 1995 and Xanthomonas cynarae (Trébaol 2000) Timilsina et al. 2018. EuroXanth COST Action 3rd Annual Conference, Sep 2019, Lednice, Czech Republic. ⟨hal-02561964⟩

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