Plant Pathology Department


Date of this Version



Published in Systematic and Applied Microbiology 29 (2006) 690–695. Copyright 2006 Elsevier GmbH. Used by permission.


In the paper by Schaad et al. [24] on reclassification of several xanthomonads, nomenclatural errors were made. The name Xanthomonas smithii subsp. citri proposed for the former taxon X. campestris pv. citri ( = X. axonopodis pv. citri) is illegitimate. Following the reinstatement of X. citri (ex Hasse 1915) Gabriel et al. [9] as a validly published name, Young et al. [34] wrote that the reinstatement of this epithet was based on a description that was inadequate in terms of modern practice for the purpose of formal classification. This report was subsequently summarized by the International Committee on the Systematics of Bacteria (ICSB) Subcommittee on the Taxonomy of the Genus Pseudomonas and Related Organisms [32] as implying rejection of the epithet, which the Subcommittee itself appeared to endorse. As we now understand, in accord with the International Code of Nomenclature of Prokaryotes (‘the Code’—hitherto the International Code of Nomenclature of Bacteria [14]) the Judicial Commission of the ICSP only may reject a name for precisely specified reasons (Rule 56a). We also misinterpreted the subsequent establishment of the pathovar ‘‘citri’’ within Xanthomonas axonopodis [29] as further evidence for rejection of reinstatement of X. citri [9]. Finally, believing that the epithet ‘‘citri’’ had been rejected, we followed rule 23a of the Code [14] and proposed an illegitimate specific epithet ‘‘smithii’’ (which also required establishing the subspecies epithet ‘‘smithii’’ replacing ‘‘malvacearum’’; see rule 13a [14]). In fact, X. citri Gabriel et al. 1989 was a legitimate, validly published name that was allowed to fall into abeyance because of the inadequacies perceived in its description. Schaad et al. [24] indicated their support for the conclusions of Gabriel et al. [9] but included DNA–DNA reassociation data indicated as necessary by for modern classification [26,31]. One purpose of this note is to recognize by effective publication the species related to pathogenic xanthomonads of citrus. The second purpose is to avoid confusion in plant pathological literature by replacing the illegitimate subspecies name X. smithii subsp. ‘‘smithii’’ with X. citri subsp. ‘‘malvacearum’’. For that purpose, corrected protologues for those species and subspecies are reported here: X. citri subsp. citri and X. citri subsp. malvacearum; X. fuscans subsp. fuscans and X. fuscans subsp. aurantifolii; and X. alfalfae subsp. alfalfae and X. alfalfae subsp. citrumelonis. We also present (Table 1) GenBank accession numbers for the intergeneric spacer (ITS) sequences for the type strains proposed in this note [24].