''Forma specialis'' (plural: ''formae speciales''), abbreviated f. sp. (plural ff. spp.) without italics, is an informal taxonomic grouping allowed by the

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN or ICNafp) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all tho ...

, that is applied to a parasite (most frequently a fungus) which is adapted to a specific host. This classification may be applied by authors who do not feel that a

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

or variety name is appropriate, and it is therefore not necessary to specify morphological differences that distinguish this form. The literal meaning of the term is 'special form', but this grouping does not correspond to the more formal botanical use of the

taxonomic rank In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of or ...

of ''forma'' or form. An example is '' Puccinia graminis'' f. sp. ''avenae'', which affects oats. An alternative term in contexts not related to

biological nomenclature Nomenclature codes or codes of nomenclature are the various rulebooks that govern the naming of living organisms. Standardizing the Binomial nomenclature, scientific names of biological organisms allows researchers to discuss findings (including ...

is physiological race (sometimes also given as biological race, and in that context treated as synonymous with biological form), Previously: Previously: except in that the name of a race is added after the binomial scientific name (and may be arbitrary, e.g. an alphanumeric code, usually with the word "race"), e.g. "'' Podosphaera xanthii'' race S". A ''forma specialis'' is used as part of the infraspecific scientific name (and follows

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

-based scientific naming conventions), inserted after the interpolation "f. sp.", as in the "'' Puccinia graminis'' f. sp. ''avenae''" example.

History, and use with "pathotype"

The ''forma specialis'' category was introduced and recommended in the ''

International Code of Botanical Nomenclature The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN or ICNafp) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all tho ...

'' of 1930, but was not widely adopted. Fungal pathogens within ''

Alternaria alternata ''Alternaria alternata'' is a fungus causing leaf spots, rots, and blights on many plant parts, and other diseases. It is an opportunistic pathogen on over 380 host species of plant. It can also cause upper respiratory tract infections and a ...

'' species have also been called pathotypes (not to be confused with pathotype as used in bacteriology) by author Syoyo Nishimura who stated:

" ch pathogen should be called a distinct pathotype of ''A. alternata''"

Some authors have subsequently used ''forma specialis'' and "pathotype" together for the species ''A. alternata'':

"Currently there are seven pathotypes of ''A. alternata'' described ..., but this term is not widely adopted. ... To further standardise the taxonomic terms used, the trinomial system introduced by Rotem (1994) is favoured. When differences in host affinity are observed within the isolates of one ... species, the third epithet, the ''forma specialis'', defines the affinity to this specific host in accordance with the produced toxin causing this affinity. When different toxins are produced on the same host, but these toxins affect different host species, the term pathotype should be used in addition. All isolates which are not confined to specific hosts and / or toxins should retain only the binomial name until such specificity is found."

References

{{reflist Taxa by rank Plant pathogens and diseases Botanical nomenclature Latin biological phrases

History, and use with "pathotype"

See also

References