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

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

grouping allowed by the

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) 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 those "trad ...

, 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 biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

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 biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in an ancestral or hereditary hierarchy. A common system consists of species, genus, family (biology), family, order (biology), order, class (b ...

of ''forma'' or form. An example is ''

Puccinia graminis Stem rust, also known as cereal rust, black rust, red rust or red dust, is caused by the fungus ''Puccinia graminis'', which causes significant disease in cereal crops. Crop species that are affected by the disease include bread wheat, durum whe ...

'' f. sp. ''avenae'', which affects oats. An alternative term in contexts not related to biological nomenclature is

physiological race In biological taxonomy, race is an informal rank in the taxonomic hierarchy for which various definitions exist. Sometimes it is used to denote a level below that of subspecies, while at other times it is used as a synonym for subspecies. It ha ...

(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 branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

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

'' f. sp. ''avenae''" example.

History, and use with "pathotype"

The ''forma specialis'' category was introduced and recommended in the '' International Code of Botanical Nomenclature'' of 1930, but was not widely adopted. Fungal pathogens within '' Alternaria alternata'' 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 Forma specialis taxa

History, and use with "pathotype"

See also

References