Committee on the Taxonomy of Plant Pathogenic
International Standards for Naming Pathovars of
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
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
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
The revisions (Young et al. 1991) accepted at the ISPP Conference on
Plant Pathogenic Bacteria, Versailles, 1992, are included in the text
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
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
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
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
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
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
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
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.
(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.
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
(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
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.
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:
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
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.
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
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
(1) Papers read to meetings, or published in minutes or abstracts of
(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.
CFBP = Collection Française de Bactéries Phytopathogènes,
Unité de Pathologie Végétale, Institut National de la
Recherche Agronomique, F-49071 Beaucouzé Cedex, France
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
(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
(4) proposes a name based on a pathovar described as a component of a
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
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
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,
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
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
(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
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
(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
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
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
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,
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.
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.