''Phoma'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of common coelomycetous soil

fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...

. It contains many

plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...

ic species.

Description

Spores In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

are colorless and

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

. The

pycnidia A pycnidium (plural pycnidia) is an asexual fruiting body produced by mitosporic fungi, for instance in the order Sphaeropsidales ( Deuteromycota, Coelomycetes) or order Pleosporales (Ascomycota, Dothideomycetes). It is often spherical or in ...

are black and depressed in the tissues of the host. ''Phoma'' is arbitrarily limited to those species in which the spores are less than 15 µm as the larger spored forms have been placed in the genus ''

Macrophoma ''Macrophoma'' is a genus of anamorphic fungi in the family Botryosphaeriaceae. Some of these species are pathogenic, for example '' M. musae'' is a banana fungus. Species *'' Macrophoma abietis'' *''Macrophoma abietis-pectinatae'' *'' Macrop ...

''. The most important species include '' Phoma beta'' which is the cause of the heart rot and blight of beets, '' Phoma batata'' that produces a dry rot of sweet potato, and '' Phoma solani''.

Taxonomy

About 140 ''Phoma'' taxa have been defined and recognized which may be divided into two large groups: (i) plurivorous fungi, generally

saprobic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...

or weakly

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

, mainly from

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

regions in Eurasia, but occasionally also found in other parts of the world (including areas with cool or warm climates); and (ii) specific pathogens of cultivated plants. However other estimates place the number of taxa closer to 3000, making it one of the largest fungal genera. Traditionally nine sections (''Phoma'', ''Heterospora'', ''Macrospora'', ''Paraphoma'', ''Peyronellaea'', ''Phyllostictoides'', ''Pilosa'', ''Plenodomus'' and ''Sclerophomella'') as described by Boerema (1997) have been recognised on morphological grounds. The number of taxa in each section varied widely, from 2 (''Pilosa'') to 70 (''Phoma''). Section Phoma itself was considered

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

. However phylogenetic studies suggest the genus is highly polyphyletic containing six distinct clades. Furthermore, taxa identified as ''Phoma'' have been identified across several different families within

Pleosporales The Pleosporales is the largest order in the fungal class Dothideomycetes. By a 2008 estimate it contains 23 families, 332 genera and more than 4700 species. The majority of species are saprobes on decaying plant material in fresh water, marine ...

, but most within

Didymellaceae The Didymellaceae are a family of fungi in the order Pleosporales. The have a world-wide distribution. Recent phylogenetic examination of some of the larger genera of the Pleosporales, particularly '' Phoma'', has led to considerable reorganisat ...

(type genus ''

Didymella ''Didymella'' is a genus of fungi belonging to the family Didymellaceae. The genus has cosmopolitan distribution. Species Species include: *''Didymella abieticola'' *''Didymella acaciae'' *''Didymella acanthophila'' *''Didymella proximel ...

''). Furthermore, the Didymellaceae segregate into 18 clusters allowing many taxa to be distributed into separate genera. Consequently, there is little justification for retaining the sections, a number of which such as '' Peyronellaea'' are now elevated to genus rank, within Didymellaceae.

Species

Species include: *''

Phoma candelariellae ''Phoma candelariellae'' is a species of lichenicolous (lichen-eating) fungus in the family Didymellaceae. It is found in the Central Anatolia Region of Turkey and in Ukraine, where it grows parasitically on the apothecia (fruiting structures) o ...

'' –

lichenicolous A lichenicolous fungus is a parasitic fungus that only lives on lichen as the host. A lichenicolous fungus is not the same as the fungus that is the component of the lichen, which is known as a lichenized fungus. They are most commonly specific t ...

on ''

Candelariella aurella ''Candelariella aurella'', the hidden goldspeck lichen or eggyolk lichen, is a yellow crustose lichen in the family Candelariaceae. It is commonly found on calcareous rock or wood or bark exposed to sunlight and which may have calcareous dust in ...

'' * '' Phoma caricae-papayae'' * '' Phoma clematidina'' * '' Phoma costaricensis'' * '' Phoma cucurbitacearum'' * '' Phoma destructiva'' * '' Phoma draconis'' * '' Phoma eupyrena'' * ''

Phoma exigua ''Phoma exigua'' ( syn. ''Ascochyta gossypii'') is a fungal plant pathogen. It causes wet weather blight in cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of ...

'' ** ''Phoma exigua'' var. ''exigua'' ** ''Phoma exigua'' var. ''foveata'' ** ''Phoma exigua'' var. ''linicola'' * '' Phoma glomerata'' * '' Phoma glycinicola'' * '' Phoma herbarum'' * '' Phoma insidiosa'' * '' Phoma medicaginis'' * '' Phoma microspora'' * ''

Phoma narcissi ''Phoma narcissi'' is a fungal plant pathogen of Narcissus, Hippeastrum and other Amaryllidaceae, where it causes a leaf scorch, neck rot and red leaf spot disease Taxonomy The USDA's Fungal Database states that ''P. narcissi'' may be a syna ...

'' * ''

Phoma nebulosa ''Phoma nebulosa'' is a fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classifie ...

'' * ''

Phoma oncidii-sphacelati ''Phoma oncidii-sphacelati'' is a fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are ...

'' * '' Phoma pinodella'' * '' Phoma scabra'' * ''

Phoma sclerotioides ''Phoma sclerotioides'' is a plant pathogen and is the culprit for brown root rot disease in, for instance, alfalfa and clover Clover or trefoil are common names for plants of the genus ''Trifolium'' (from Latin ''tres'' 'three' + ''folium'' 'l ...

'' * '' Phoma strasseri'' * '' Phoma tracheiphila'' * ''

Phoma multirostrata ''Phoma'' is a genus of common coelomycetous soil fungi. It contains many plant pathogenic species. Description Spores are colorless and unicellular. The pycnidia are black and depressed in the tissues of the host. ''Phoma'' is arbitrarily l ...

References

Bibliography

* Boerema, G. H.; de Gruyter, J.; Noordeloos, M. E.; Hamers, M. E. C. 2004. ''Phoma'' Identification Manual: Differentiation of Specific and Infra-specific Taxa in Culture. CABI. * * {{Taxonbar, from=Q2066891 Dothideomycetes genera Fungal plant pathogens and diseases Lichenicolous fungi Taxa described in 1880 Taxa named by Pier Andrea Saccardo