New Zealand strains of plant pathogenic bacteria classified by multi‐locus sequence analysis; proposal of <i>Xanthomonas dyei</i> sp. nov.

Abstract

Strains of Xanthomonas isolated in New Zealand from diseased endemic and introduced plants, investigated in a multi‐locus sequence analysis (MLSA), were distributed primarily in two species. Strains from Dysoxylum , Hardenbergia , Liquidambar , Magnolia and Mahonia were members of Xanthomonas arboricola . Strains of Xanthomonas campestris pv. laureliae , X . campestris pv. eucalypti and strains from Aralia , Diospyros , Dysoxylum , Eriostemon , Eucalyptus , Metrosideros and Olea formed a population distinct from all known Xanthomonas spp. These latter strains have a unique fatty acid methyl ester profile and are considered to be members of a new Xanthomonas species, for which the name Xanthomonas dyei is proposed. Xanthomonas campestris pv. eucalypti and X . campestris pv. laureliae are considered to be pathovars of the new species and their reclassification as X . dyei pv. eucalypti and X . dyei pv. laureliae , respectively, is proposed. Strains previously identified as Pseudomonas syringae pv. dysoxyli from Dysoxylum spectabile , including the pathotype strain, were examined and found not to represent the pathogen originally described as P . dysoxyli . Other strains (proved to be pathogenic) from diseased D. spectabile , corresponding to the original description of P . dysoxyli , are members of X . dyei and the new combination X . dyei pv. dysoxyli is proposed. The geographic and evolutionary origins of X . dyei , apparently endemic to Australasia, and the adaptation of strains to the introduced host plants Aralia , Diospyros , Eriostemon , Metrosideros and Olea , are discussed. The origins of the X. arboricola strains isolated from Dysoxylum , Hardenbergia , Liquidambar , Magnolia and Mahonia pose a conundrum.