Committee on the Taxonomy of Plant Pathogenic Bacteria

International Standards for Naming Pathovars of Phytopathogenic Bacteria

J.M. Young, C.T. Bull, S.H. De Boer, G. Firrao, L. Gardan, G.E. Saddler, D.E. Stead and Y. Takikawa

The International Standards for Naming Pathovars (Dye et al. 1980) were adopted by resolution of a meeting held at the ISPP Congress, Melbourne, 1983. The revision of the Standards (Young et al. 1991) was adopted by resolution of a meeting held at the ISPP Conference on Plant Pathogenic Bacteria, Versailles, 1992.

The text below was edited by the present Committee to take account of the passage of time which has made some parts of the original text redundant. No substantive changes have been made to the Standards as revised.

20 December 2001

This is a statement on behalf of the Executive Committee (1980) of the International Society for Plant Pathology by the ISPP Committee on Taxonomy of Phytopathogenic Bacteria.

The 1976 revision of the International Code of Nomenclature of Bacteria (Lapage et al. 1975) provides that 'after 1 January 1980, priority of publication shall date from 1 January 1980' and 'On that date all names published prior to 1 January 1980 and included in the Approved Lists of Bacterial Names of ICSB [International Committee on Systematic Bacteriology] shall be treated .... as though they had been validly published for the first time on that date...... Those names validly published prior to 1 January 1980 but not included in the Approved Lists will have no further standing in nomenclature.. and will thus be available for reuse in the naming of new taxa.'ln correspondence and discussion with the committee of the Judicial Commission of the ICSB charged with recommending the Approved Lists to the Judicial Commission, the Ad Hoc Committee on Approved Lists, it became apparent that they would accept only lists of species or subspecies the names of which had been validly published, that are represented by authentic, extant type or neotype cultures and that have modern descriptions by which they can be differentiated readily from other species or subspecies using practical, laboratory diagnostic methods.

In response to this, the Executive Committee of the International Society for Plant Pathology set up a Committee on Taxonomy of Phytopathogenic Bacteria whose initial brief was to consider the consequences of the 1976 revision of the Code for plant pathologists and to make recommendations on the names to be submitted for the Approved Lists. The committee met in February 1978, first in open session with the Subcommittee on Bacterial Taxonomy of the American Phytopathological Society and then in closed session. It recommended submitting to the ICSB Ad Hoc Committee three lists:

List 1: Names of approved species for retention.

List 2: Names of species of plant pathogens which ' cannot be adequately differentiated by means ofphenotypic (laboratory, diagnostic) characters but which have been long used by, and are essential to plant pathologists for naming bacteria that cause different and differentiable diseases. (There are indications from present work, and particularly DNA homology, that reinstatement of some of them may be required at species level and they are therefore conserved for this purpose and for use in any special purpose, infrasubspecific classification used to express the pathogenic properties of these bacteria). If any of these names are proposed after 1980 as a species name, the description of that species must include the pathogenic properties associated with the original name.

List 3: Names of species of plant pathogens the generic position of which is uncertain but which are retained so that plant pathologists can refer to the pathogens of the diseases with which they are associated.

Lists 1 and 3 met the criteria established by the Ad Hoc Committee but by these same criteria the definition of list 2 implied a request to the Judicial Commission for the inclusion in the Approved Lists of infrasubspecific, names, exceptionally, for plant pathogens.

These recommendations were put by the ISPP Executive Committee to the International Conference of Plant Bacteriology at a meeting in Angers in August 1978, which endorsed them and added that should the Judicial Commission, at its meeting in Munich in September 1978, not accept list 2 it should be asked to recommend either the inclusion of the taxon pathovar, for these nomenspecies within the rules of the Code - which would, in effect, retain the list 2 names after 1980 - or to give an assurance that should the necessity arise, the Judicial Commission would view sympathetically any request to reject the re-use of any name in list 2 as a species or subspecies for a different bacterium, on the grounds that such a re-used name was a nomen perplexum (Rules 56a and 57c of the 1976 revision of the Code).

The recommendations of the Angers meeting were put, through the ISPP, to the Judicial Commission who accepted lists 1 and 3 for the Approved Lists but not list 2. The Commission was not prepared to alter the rules of the Code to include the taxon pathovar because of the precedent this could set for the inclusion of other infrasubspecific subdivisions. It considered that the ISPP had two alternatives depending on current information, viz. to reduce the various list 2 nomenspecies either to subspecies, a category covered by the rules of the Code, or to the rank of pathovar, an infrasubspecific subdivision not covered by the rules of the Code.

The consensus of opinion of ISPP members and its committee on bacterial taxonomy was that the pathovar designation most accurately records the known status of the list 2 nomenspecies and that formal recognition is essential to avoid confusion in the nomenclature. In order to formalise the use of pathovar names, the ISPP, through its Executive Committee and its Committee on Taxonomy of Phytopathogenic Bacteria, has decided to publish a list of pathovar names and standards, to be known as the International Standards for Naming Pathovars of Phytopathogenic Bacteria. The pathovar scheme does not conflict with the Approved Lists of Bacterial Names but retains in general usage those nomenspecies which are essential for naming bacteria that cause different and differentiable diseases. Also the International Standards for Naming Pathovars of Phytopathogenic Bacteria do not conflict with the International Code of Nomenclature of Bacteria; the rules for the standards are adapted from the Code and are so written that if the Code ever does expand to assume authority over the infrasubspecific subdivisions, the pathovar standards would be transferred easily to the Code.

The ISPP committee realises that more discussion at a general meeting of the Society than could take place at Angers would have been desirable but in view of the imminent necessity for some positive action to prevent confusion in the naming of the pathogens not included in the Approved Lists, they have decided to promulgate the Standards as given in Appendix 1 to this statement. Further discussion and, if so decided, revision of it should take place at the next plenary session of the ISPP International Conference on Phytopathogenic Bacteria. (A list of pathovar names valid as from 1 January 1980 was given in an Appendix II of the original statement. This list has been deleted from the current text. A full list of names of plant pathogenic bacteria is given in Young et al. 1996) also available at the ISPP website).

The International Standards for Naming Pathovars of Phytopathogenic Bacteria

The revisions (Young et al. 1991) accepted at the ISPP Conference on Plant Pathogenic Bacteria, Versailles, 1992, are included in the text below.

1. Application
These Standards for Naming Pathovars (hereinafter referred to as the Standards) are intended to supplement the Rules and Recommendations of the International Code of Nomenclature of Bacteria (1975) (hereinafter referred to as the Code) in order to provide for a consistent and ordered system of names for strains of phytopathogenic bacteria at infrasubspecific level, based on accepted differences in pathogenicity to plants. The Standards are derived in general from the Principles which form the basis of the Code; they are not intended to replace or modify in any way the existing Rules and Recommendations of the Code. These Standards will apply from 1 January 1980.

2. Alterations
Alterations to these Standards will be made only by the International Society for Plant Pathology(ISPP). Proposals to alter the Standards should be made through the Committee on Taxonomy of Phytopathogenic Bacteria of the ISPP (hereinafter referred to as the Taxonomy Committee), who will ensure effective publication of proposed alterations prior to submission for acceptance or rejection by a Conference or Congress of the ISPP.

3. Names Contrary to the Standards
Names contrary to a Standard should not be used, except that the Taxonomy Committee may make exceptions. The procedure for establishing an exception shall be the same as that laid down for making an alteration.

4. Interpretation of Standards
In the apparent absence of an appropriate Standard, or where interpretation of a Standard appears ambiguous, a request for alteration or exception to the Standards to provide suitable clarification should be made to the Taxonomy Committee, who will ensure effective publication of their decision on the request prior to submission for acceptance or rejection by a Conference or Congress of the ISPP. In giving opinions and in accepting or rejecting them, full weight will be given to any relevant or comparable rules of the International Code of Nomenclature of Bacteria (1975).

5. Definition of Pathovar
The term pathovar is used to refer to a strain or set of strains with the same or similar characteristics, differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one or more plant hosts.

Classification of a taxon as a pathovar does not exclude recognition of differences in biochemical, aerological or other non-pathogenic characters between that and other pathovars of the same species or subspecies, but implies that at infrasubspecific level other differences are considered to have less taxonomic significance in comparison to differences in pathogenicity.

Usually pathovars are distinguished in terms of proved differences in host range. However, clear differences in symptomatology on the same plant species (e.g. Xanthomonas campestris pv. oryzae and X. campestris pv. oryzicola) can warrant different pathovar designations.

This definition allows alternative divisions of pathogenic species or pathovars into races. A ‘race’ of a bacterium is a collection of strains which differ from others within a bacterial species or pathovar in their host specialization to cultivars or germplasm. Races are identified through the use of plant host differentials which may be cultivars or other identifiable germplasm. Races have no nomenclatural standing. A race should be designated with letters or numbers.

The term ‘pathogenic group’ may be useful to designate informally a set of organisms having certain characteristics in common, if it is used with care and exact definition to avoid ambiguity (Lapage et al. 1975, p. 127). The term is an informal one which has no nomenclatural standing and is not a substitute term for race.

The term ‘forma specialis’ (syn. special form) is not a substitute for pathovar or race for phytopathogenic bacteria. It is applied to pathogens which are specific for a particular host. The term is defined by Lapage et al. (1975, p.126).

6. Naming of Pathovars
Pathovar names must be treated as Latin. The name of a pathovar is a ternary or quaternary combination, consisting of the name of the genus followed by a specific epithet, and where appropriate a subspecific epithet preceded by the abbreviation 'subsp.' and finally by the pathovar epithet preceded by the abbreviation 'pv.' (pathovar).

Note: The first time a name is used in a publication, it should be given in full with its authority. Subsequently, where there is no risk of confusion, the examples below offer acceptable abbreviations.

Example: Pseudomonas syringae pv. lachrymans abbreviated to:
1) P.s. pv. lachrymans;
2) P.s. lachrymans;
3) pv. lachrymans

7. Formation of Pathovar Epithets
A pathovar epithet is a single word in Latin or Latinized form, and must be treated in one of the following ways:
(1) As an adjective in agreement with the generic name.
Example: insidiosum in Corynebacterium michiganense pv. insidiosum.
(2) As a substantive in apposition in the nominative case.
Example: maculicola in Pseudomonas syringae pv. maculicola.
(3) As a substantive in the genitive case.
Example: oryzae in Xanthomonas campestris pv. oryzae.

If a pathovar epithet is formed from two or more words, the words used must refer to a single concept and must be joined according to the established principles of Latin or Latinization to form a compound; the components of a compound must not be hyphenated. If an epithet has been hyphenated it is not to be rejected, but treated as an orthographic or typographic error and corrected.
Example: atropurpurea in Pseudomonas syringae pv. atropurpurea.

8. Suitability of Pathovar Epithets
No two pathovars within the same species or subspecies may bear the same pathovar epithet.

It is recommended that authors naming new pathovars should:
(1) Avoid the use of a pathovar epithet already in use within another species.
(2) Form new pathovar epithets that are easy to pronounce.
(3) Avoid epithets that are unduly long, or that are only slightly different from other pathovar epithets based on the same word, name or concept.
Example: maculifoliigardeniae is unduly long; glycines is similar to glycinea.
(4) Form epithets that give some indication of the pathogenicity of the pathovar, particularly by derivation from the name of the susceptible host family, genus or species. Where an author chooses to create an epithet by derivation from the scientific binomial of the host species for that pathovar, it should be a compound formed from the two names of the scientific binomial used as a substantive in the genitive case.
Example: vitiswoodrowii in Xanthomonas campestris pv. vitiswoodrowii,. vignaeradiatae in Xanthomonas campestris pv. vignaeradiatae.

9. Designation of Type Strains of Pathovars - Pathotypes
In order to reserve the use of the terms ‘type strain’, ‘holotype’, ‘proposed neotype’, etc., strictly for use when referring to the designated nomenclatural types of a species or subspecies, the nomenclatural type of a pathovar, which in all instances consists of a designated strain and its descendants maintained as a living pure culture, is named as follows:
(1) Holopathotype
The strain upon which the description of the pathovar name is based should be designated in the original publication where the pathovar name is proposed formally; the strain so designated is the holopathotype strain.
(2) Monopathotype
If the original author described only a single strain and did not designate it as the holopathotype, then this strain shall be accepted as the pathotype and may be referred to as the monopathotype strain.
(3) Lectopathotype
If no holopathotype exists, one of the strains on which the original author based his description may be designated later as the pathotype strain by the original or by a subsequent author. This strain shall be accepted as the pathotype strain and may be referred to as the lectopathotype.
(4) Neopathotype
A proposed neopathotype strain is one proposed by valid publication (see Standard 17) to represent a pathovar where none of the strains upon which the original description was based can be located.

Publication must include citation of the original author(s) of the pathovar name, a full description (or reference to a previously effectively published description) of the pathovar, and a record of one or more permanently established culture collections where the strain has been deposited. A proposed neopathotype becomes established (established neopathotype) two years after its proposal, provide the Taxonomy Committee has not received any objection in writing during that period.

The proposer of a neopathotype strain should document attempts to locate a pathotype from among the strains upon which the original description was based, and should show that the proposed neopathotype strain conforms closely to the original description. A neopathotype strain should be selected as typical of the pathovar. A strain suggested as a neopathotype (suggested neopathotype) that is not formally proposed in accordance with the requirements of these Standards has no standing in nomenclature until formally proposed and established.

The pathotype strain is the type strain, or name-bearer, of the pathovar, designated for nomenclatural purposes (Sneath, 1984). The circumscription of a pathovar may include characters not expressed by the pathotype strain. In the event that the pathovar is sub-divided, the allocation of the pathotype strain determines the allocation of the name.

The term 'reference strain' is not a substitute for pathotype, as the term is used too extensively in a general sense to have the nomenclatural intent associated with a pathotype strain.

10. Rediscovery of a Pathotype Strain
If an original strain that should constitute the pathotype of a pathovar is discovered subsequent formal proposal or establishment of a neopathotype for that pathovar, the matter shall be referred immediately to the Taxonomy Committee.

11. Change in Characters of Pathotype and Neopathotype Strains
If a pathotype or neopathotype strain has become unsuitable due to changes in its characters or for other reasons, then the matter should be referred to the Taxonomy Committee, which may decide to take action leading to replacement of the strain.

12. Correct Name of a Pathovar
Each pathovar can bear only one correct pathovar epithet, that is the earliest published in accordance these Standards. In any reclassification, the pathovar retains this epithet unless a change is required by these Standards (see Standard 26).

13. Priority of Pathovar Names
The date of a name is that of its valid publication'. For the purpose of priority, only legitimate names are taken into consideration.

Valid publication of names which are in accordance with these Standards shall be deemed to commenced on 1 January 1980. All names published prior to 1 January 1980 and included in the published List of Pathovar Names of the ISPP (1980) (hereinafter referred to as the ISPP List (1980)) shall be treated for all nomenclatural purposes as though they had been published for the first time on that date. If two names on the ISPP List (1980) later compete for priority, the name published first before 1 January 1980 shall have priority.

14. Automatic Creation of Pathovar Names
The valid publication of a pathovar name that excludes the type strain of the parent species (or subspecies) shall, in the case of a plant pathogenic species, automatically create a pathovar which includes the type strain and bears the same pathovar epithet as the specific (or sub-specific) epithet. Example: Publication of Pseudomonas marginalis pv. alfalfae Shinde & Lukezic 1974 automatically created P. marginalis pv. marginalis (Brown 1918) Stevens 1925.

Pathovar as an infrasubspecific term is explicitly a special purpose classification and not part of the taxonomic hierarchy. It makes no sense, and is confusing, to create pathovar names for subpopulations of species for which there is no evidence of pathogenic character. Non-pathogenic strains of P. fluorescens and Erwinia herbicola are not automatically reclassified as P. fluorescens pv. fluorescens and E. herbicola pv. herbicola

15. Effective Publication
For the purposes of these Standards, effective publication is accomplished by making generally available to the scientific community printed material for the purpose of providing a permanent record. The following means of publication are specifically excluded as not acceptable:
(1) Papers read to meetings, or published in minutes or abstracts of meetings.
(2) Labels on specimens in herbaria or culture collections and information in catalogues of herbaria or collections.
(3) Papers in publications which are ephemeral or not readily available, or publications whose editorial policy is other than scientific (e.g. newsletters, newspapers).
(4) Information connected with Patents.
Note: When a name of a new pathovar is published in a work written in a language unfamiliar to a majority of workers in bacteriology, it is recommended that the author(s) include in the publication a description in a more familiar language.

16. Date of Publication
The date of publication of a scientific work is the date of publication of the printed material. The date given to the work containing the name or epithet must be regarded as correct in the absence of proof to the contrary. Any dispute concerning priority will be decided by the precise date of publication of the printed material.

The date of acceptance of an article for publication does not indicate the effective date of publication and has no significance in the determination of the priority of publication of names.

17. Valid Publication
A pathovar name is validly published only if the following conditions have been satisfied:
(1) Publication is effective (see Standard 15).
(2) The proposed pathovar name is based on and accompanied by a description of the organism which allows it to be recognised if isolated again and allow it to be distinguished from other pathovars. Alternatively, reference to a previously effectively published description is acceptable. The description should include evidence of species identification according to the prescriptions of the Code. It should also include an account of the verification of Koch's postulates; the procedures by which pathogenicity can be demonstrated, giving details of inoculum preparation and growing conditions of host plants, specifying susceptible cultivars, and giving a precise description of inoculation conditions and pre-incubation and post-incubation conditions. There should be a clear description of resulting symptoms, comparing them with those of the naturally occurring disease. Attention is drawn to Ercolani (1984) in which methods are described which allow compatible and incompatible reactions to be distinguished. It is recommended that, where possible, strains of existing pathovars from related host plants be cross-inoculated into the host of the putative pathovar, and the behaviour of the strains under consideration to the hosts of these existing pathovars be investigated to guard against the generation of synonyms.
(3) The pathotype strain is designated as part of the description.
(4) The pathotype strain has been accepted by one or more permanent culture collections which are designated in the published description of the pathovar. It is recommended that where possible at least five cultures representing the geographic and host range of the pathovar should be selected for deposition in permanent collections.

Note: It is intended that the Taxonomy Committee will publish from time to time a list of culture collections that are considered suitable for deposition of pathotype strains. Minimum suitability is considered to be that the collection be independent, permanent and publishes a catalogue.

Examples:

CFBP = Collection Française de Bactéries Phytopathogènes, Unité de Pathologie Végétale, Institut National de la Recherche Agronomique, F-49071 Beaucouzé Cedex, France (formerly CNBP)

ICMP = International Collection of Micro-organisms from Plants, Landcare Research, Private Bag 92170, Auckland, New Zealand (formerly PDDCC)

NCPPB = National Collection of Plant Pathogenic Bacteria, Central Science Laboratory, Ministry of Agriculture, Fisheries and Food, Sand Hutton, York, YO4 1LW, United Kingdom

18. Invalid Publication
Publication of a proposed pathovar name is invalid if the author:
(1) does not unequivocally and unconditionally indicate that a new name is proposed;
(2) mentions a new name merely incidentally;
(3) proposes a name to be used as an alternative or interim name subject to resolution of one of more taxonomic questions left open by the proposer;
(4) proposes a name based on a pathovar described as a component of a mixed culture.

19. Citation of the Name of a New Pathovar
An author should indicate that a name is proposed for a new pathovar by the addition of the abbreviation ‘pv. nov.' for pathovarietas nova.

Example: 'The name Xanthomonas campestris pv. caladiae pv. nov. is proposed for this pathovar.'

Authors should not include any other form of citation when proposing a new pathovar name. The purpose of citation is to refer, by the name(s) of the author(s), to a publication in which the new pathovar is proposed. Thus authors should not append their own, nor their colleagues' names, when proposing new pathovars.

Example: If Tasman (1980) proposes the name 'Xanthomonas campestris pv. alba Tasman & Cook pv. nov.' the formal name would be Xanthomonas campestris pv. alba Tasman 1980 (see Standard 20).

20. Citation of Names of Previously Proposed Pathovars
The citation of the name of a pathovar that has been proposed previously should include the name of the author(s) of the publication in which the pathovar epithet was proposed formally, followed by the date of publication. This enables the original description to be found, the year of publication to be verified, and the use of the name by different authors to be distinguished. Full citation of the publication should include the number of the page in the body of the text (not the summary or abstract) on which the name was proposed.

Example: In a publication by Wilson, the statement...... Xanthomonas campestris pv. cannabina Severin 1978, 13' would indicate that the name was proposed by Severin in 1978, and that the proposal can be found on page 13 of the publication in which Severin described and proposed the new pathovar. The publication by Severin should be listed in the references given in Wilson's publication.

21. Citation of the Name of a New Combination
An author who proposes the transfer of a pathovar from one species or subspecies to another should indicate the new combination by using the abbreviation 'comb. nov.', for combinatio nova, following enclosure in parentheses of the name(s) of the author(s) of the pathovar epithet in its original position.

Example: lf Wilson (1980) proposes that Xanthomonas campestris pv. cannabina Severin l978 should be reclassified as a pathovar of Xanthomonas fragariae Kennedy & King 1962, the statement,'lt is proposed that this organism should be named Xanthomonas fragariae pv. cannabina (Severin 1978) comb. nov.', will indicate the proposed new combination in Wilson's publication.

22. Citation of the Name of a Previously Reclassified Pathovar
The citation of the name of a pathovar of a species or subspecies which was originally classified as a pathovar of a different species or subspecies should include the name of the author(s) of the publication in which the pathovar epithet was formally proposed, and the date of the publication, in parentheses; followed by the name of the author(s) of the publication in which the new combination was proposed, and the date of that publication. Full citation of the publications should include the appropriate page numbers (see Standard 20).

Example: In a publication by Marshall, the statement...... Xanthomonas fragariae pv. cannabina (Severin 1978, 13) Wilson 1980, 7' would indicate that the pathovar epithet cannabina was proposed by Severin in 1978 and transferred to Xanthomonas fragariae by Wilson in 1980 and that the proposal to reclassify the pathovar can be found on page 7 of the journal containing Wilson's publication. The publications by Severin and Wilson should be listed in the references given in Marshall's publication.

23. Citation of a Pathovar in the ISPP List (1980)
The citation of a name that is included in the ISPP List (1980) can be made in the following ways:
(1) By including the name(s) of the original author(s) and date of publication followed by ISPP List, in parentheses.
Example: Pseudomonas syringae pv. aceris (Ark 1939) Young, Dye & Wilkie 1978 (ISPP List, 1080).
(2) By addition simply of 'ISPP List, 1980' in parentheses.
Example: Pseudomonas syringae pv. aceris (ISPP List, 1980).

24. Emendation of Characters of a Pathovar
If an emendation is made of the characters or circumscription of a pathovar, the author(s) responsible for the change may be indicated by the addition to the author citation of the abbreviation 'emend'. followed by the name(s) of the emending author(s) and the year of publication of the emendation.

Example: If Brown 1980 were to emend the hypothetical name Pseudomonas syringae pv. mahoniae

Smith 1979, the citation would be Pseudomonas syringae pv. mahoniae Smith 1979 emend. Brown 1980.

25. Reclassification of a Designated Pathovar
In any reclassification, if the designated nomenclatural pathotype of a pathovar is excluded, the name of that pathovar must be changed. The retention of a name in a sense that excludes the pathotype can be effected only by conservation and only by the Taxonomy Committee, who will establish a new pathotype.

26. Change of Pathovar Name
A change of the name of a pathovar is not warranted by an alteration of the diagnostic characters or of the circumscription, but may be required by:
(1) an opinion of the Taxonomy Committee (see Standard 25);
(2) transfer to another species or subspecies (see Standard 28);
(3) union with another pathovar (see Standard 29).

27. Division of a Pathovar
When a pathovar is divided into two or more new pathovars the original pathovar epithet must be-retained for that new pathovar which contains the designated pathotype strain.

28. Transfer of a Pathovar
When a pathovar is transferred to another species or subspecies, or when the species or subspecies in which it is included is transferred to another genus or in any other way changed, the epithet of the pathovar must be retained unless the resulting combination would be a junior homonym, in which instance a new epithet must be chosen by the author making the change.

29. Union of Pathovars
(1) If two or more pathovars are united in one pathovar the earliest legitimate epithet is retained.
(2) If more than one of these legitimate names is included in the ISPP List (1980) that epithet first published prior to publication of the list whether as a specific, subspecific or pathovar epithet, is retained.
(3) If epithets to be united are of the same date the author who first unites the pathovars can choose one of them and that choice must be followed.

30. Changes in Rank
When a species or subspecies is lowered in rank to a pathovar, the specific or subspecific epithet must be retained as the epithet of the pathovar unless the resulting combination is illegitimate.

Example: Pseudomonas papulans Rose 1917 became Ps. syringae pv. papulans (Rose 19 17) Dhanvantari 1977.

Note: When a pathovar is elevated in rank to species or subspecies it comes under the aegis of the Code.

31. Illegitimate Pathovar Names
A name contrary to a Standard is illegitimate and may not be used. A pathovar epithet is illegitimate if it:
(1) duplicates a pathovar epithet published validly for a pathovar of the same species or subspecies but which is a different bacterium whose name is based on another pathotype;
(2) applies to a pathovar which, as circumscribed by the author, includes the nomenclatural pathotype of a different pathovar name which the author ought to have adopted under one or more of the rules of these Standards;
(3) is a letter, number or an ordinal adjective used for enumeration.

Note: The epithet of a pathovar is not rendered illegitimate by publication in a species or subspecies name which is illegitimate.

32. Replacement of a Pathovar Epithet
A pathovar epithet that is illegitimate according to Standards 31 and 34 is replaced by the earliest legitimate epithet; if no such epithet exists one must be chosen.

33. Retention of a Pathovar Epithet
A legitimate name may not be replaced merely because it no longer describes the organism, is difficult to pronounced is inappropriate, has been cited incorrectly or because another name (i.e. a synonym) is better known.

34. Rejection of a Pathovar Epithet
Only the Taxonomy Committee can place a name on a list of rejected names which they can do for various reasons including that it is an ambiguous, doubtful or perplexing name or a name causing confusion.

35. Conservation of a Pathovar Epithet
Only the Taxonomy Committee can place names on a list of conserved names. This they can do, if the application of the rules would otherwise lead to confusion. Such conserved names must be used instead of all others.

SUPPLEMENT: Replacement of Pathotype Strains of Pathovars of Plant Pathogenic Bacteria

The International Standards for Naming Pathovars of Phytopathogenic Bacteria provide for the replacement of a pathotype strain (Standard 11) if it has become unsuitable due to changes in its character, or for other reasons. Replacement of pathotype strains is a function of the Committee on Taxonomy of Phytopathogenic Bacteria (Dye et al., 1980) of the International Society for Plant Pathology. Since 1980, information has been received that the pathotype strains of the following pathovars are unsatisfactory, either because the strains are unrepresentative, being members of other pathovars or species, or non-pathogenic, or for both of these reasons. Thus, neopathotype strains are needed to replace the pathotype strains listed below. The persons reporting the deficiencies in the existing pathotypes are shown in parentheses. Proposals for alternative neopathotype strains are invited. Submissions on neopathotypes for these pathovars should be made to the convener of the Committee. If none are forthcoming, the Subcommittee will propose such strains. In addition, the Subcommittee requests that the Convener be informed of any other pathotype strains that may not be representative of their pathovar.

Strain designations in the lists refer to the following culture collections:

ATCC - American Type Culture Collection, Rockville, Maryland, USA.

ICMP - International Collection of Microorganisms from Plants, DSIR, Auckland, New Zealand (formerly PDDCC).

NCPPB - National Collection of Plant Pathogenic Bacteria, Harpenden, England.

Pseudomonas syringae pv. lachrymans ATCC 7386; ICMP 3988; NCPPB 537 is not representative of the pathovar (J.M. Young).

Pseudomonas syringae pv. morsprunorum ATCC 19322; ICMP 5795; NCPPB 48 is not representative of the pathovar (R. Samson, J.M. Young).

Pseudomonas syringae pv. striafaciens ATCC 10730; ICMP 3961; NCPPB 1898 is an avirulent strain (R.A. Lelliott, J.M. Young)

Xanthomonas campestris pv. carotae ICMP 5723; NCPPB 1422 is not representative of the pathovar (L. Claflin, J.M. Young).

Dye, D. W., Bradbury, J. F., Goto, M., Hayward, A. C., Lelliott R. A. and Schroth, M. N. 1980. International standards for naming pathovars of phytopathogenic bacteria and a list of pathovar names and pathotype strains. Rev. Pl. Pathol. 59:153-168.

Lapage, S. P., Sneath, P. H. A., Lessel, E. F., Skerman, V. B. D., Seeliger, H. P. R., and Clark, W. A. (1976 Revision) 1975. International Code of Nomenclature of Bacteria. American Society for Microbiology, Washington, DC. 180 pp.

Young, J. M., Bradbury, J. F., Davis, R. E., Dickey, R. S., Ercolani, G. L., Hayward, A. C., and Vidaver, A. K. 1991. Nomenclatural revisions of plant pathogenic bacteria and list of names 1980-1988. Rev. Pl. Pathol. 70:211-221.

Young, J.M., Saddler, G.S., Takikawa, Y., De Boer, S.H., Vauterin, L., Gardan, L., Gvozdyak, R.I., and Stead, D.E. (1996). Names of plant pathogenic bacteria 1864-1995. Rev. Pl. Pathol. 75: 721-763.