''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, 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 or

variety Variety may refer to: Arts and entertainment Entertainment formats * Variety (radio) * Variety show, in theater and television Films * ''Variety'' (1925 film), a German silent film directed by Ewald Andre Dupont * ''Variety'' (1935 film), ...

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, order, class, phylum, kingdom, domain. While ...

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 ...

'' f. sp. ''avenae'', which affects

oat The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and pseudocereals). While oats are suitable for human con ...

s. An alternative term in contexts not related to

biological nomenclature Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms. To an end-user who only deals with names of species, with some awareness that species ...

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 ''Podosphaera fuliginea'' (also known as ''Podosphaera xanthii'') is a plant pathogen that causes powdery mildew on cucurbits. ''Podosphaera fuliginea'' and ''Erysiphe cichoracearum'' are the two most commonly recorded fungi causing cucurbit powd ...

'' 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 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 ...

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

Alternaria alternata ''Alternaria alternata'' is a fungus which has been recorded causing leaf spot and other diseases on over 380 host species of plant. It is an opportunistic pathogen on numerous hosts causing leaf spots, rots and blights on many plant parts. It ...

'' species have also been called pathotypes (not to be confused with

pathotype A pathovar is a bacterial strain or set of strains with the same or similar characteristics, that is differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one o ...

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