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A pathovar is an infrasubspecific grouping of bacterial strains distinguished by disease responses in one or more hosts. The criterion concerns pathogenic characteristics and bacterial host range, rather than simply the collection from which a strain came. The 2022 revision of the prokaryotic naming code lists pathovar in its advice on infrasubspecific subdivisions; Rule14a places designations below subspecies outside the code's principal Rules and Recommendations.^[ref]

The name Pseudomonas syringae pv. tomato DC3000 shows the levels of information. Pseudomonas syringae is the species designation, pv. tomato supplies the pathovar designation and DC3000 specifies the bacterial strain. The published DC3000 genome study describes disease on both tomato and Arabidopsis thaliana.^[ref] The word tomato in the name therefore does not mean that only tomato can be affected.

A bacterial host range observation is bounded by the hosts and conditions tested. If two strains share a species name but produce different responses across a host panel, the panel can reveal a pathogenic distinction. It does not by itself establish that the strains are genetically identical within each group, nor determine responses in every untested host. A pathovar designation summarizes a biological pattern while the individual strain record preserves which material was actually measured.

A subspecies is a named taxon at a taxonomic rank below species. It distinguishes a subdivision within a species under a stated classification. The rank does not itself specify one universal percentage of sequence similarity, degree of reproductive isolation or age of divergence.^[ref]

A concrete naming convention comes from prokaryotic nomenclature. The Code forms a subspecies name from the genus name, specific epithet, abbreviation subsp. and subspecific epithet. It separately states that a subspecies containing the species' type bears the same epithet as the species. Naming conventions and the biological evidence used to recognize a subdivision are different matters.^[ref]

An original hypothetical example uses genus labelG, species epithetb and a proposed second subgroup epithetc. The name pattern is G b subsp. c; the type-containing subgroup has the pattern G b subsp. b. These are placeholders illustrating the rule, not asserted validly published taxon names.

A second example separates a rank from a measurement. Suppose two sampled populations have trait means10 and12 units but overlapping ranges. The means alone do not determine whether they should be named as subspecies, treated as variation within an undivided species or recognized differently using additional evidence. Sampling, inherited differences and the chosen taxonomic framework still need to be examined.

A strain and a subspecies also supply different kinds of reference. Many independently maintained strains can be placed within one subspecies; culture accession numbers do not create additional taxonomic ranks. The type strain anchors the relevant name under the prokaryotic rules, while experiments determine properties of the actual material.^[ref]

The applicable nomenclatural code should accompany a precise naming claim. The prokaryotic example explains one system's rules; it does not impose every one of those conventions on all other groups of organisms.