''Phoma'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of common coelomycetous soil

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

. It contains many

plant pathogen Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...

ic species.

Description

Spores In biology, a spore is a unit of sexual (in fungi) 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 plant ...

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 inve ...

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 The micrometre (Commonwealth English as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American English), also commonly known by the non-SI term micron, is a unit of length in the International System ...

as the larger spored forms have been placed in the genus '' Macrophoma''. 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 ''Phoma'' is a genus of common coelomycetous soil fungus, 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 arbitra ...

''.

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 (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

, mainly from

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

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 is a term used for a taxonomy (biology), 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, uncertainty ...

. 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 (biology), order in the fungal class Dothideomycetes. By a 2008 estimate, it contained 23 family (biology), families, 332 genera and more than 4700 species. The majority of species are saprobes on decaying pl ...

, but most within Didymellaceae (type genus '' Didymella''). 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.

Selected species

Species include: *'' Phoma candelariellae'' – lichenicolous on '' Candelariella aurella'' * '' Phoma caricae-papayae'' * '' Phoma costaricensis'' * '' Phoma cucurbitacearum'' * '' Phoma destructiva'' * '' Phoma draconis'' * '' Phoma eupyrena'' * ''

Phoma exigua ''Boeremia exigua'' is the type species of the fungus genus, '' Boeremia,'' in the Didymellaceae family. It was first described as ''Phoma exigua'' by John Baptiste Henri Joseph Desmazières in 1849, and transferred to the genus, ''Boeremia'' ...

'' ** ''Phoma exigua'' var. ''exigua'' ** ''Phoma exigua'' var. ''foveata'' ** ''Phoma exigua'' var. ''linicola'' * '' Phoma fuliginosa'' – lichenicolous on '' Caloplaca trachyphylla'' * ''

Phoma glomerata ''Phoma glomerata'' is a species of fungus that belongs to the family Pleosporaceae. It is a common plant pathogen but it can be found in temperate environments worldwide. ''Phoma glomerata'' grows in soil, plants, marine environments, inorganic ...

'' * '' Phoma glycinicola'' * ''

Phoma herbarum ''Phoma herbarum'' is a fungal plant pathogen infecting various plant species, including ''Alchemilla vulgaris'', '' Arabis petraea'', '' Arenaria norvegica'', ''Armeria maritima'', ''Bartsia alpina'', ''Capsella bursa-pastoris'', ''Erysimum'', ' ...

'' * '' Phoma insidiosa'' * '' Phoma microspora'' * '' Phoma narcissi'' * '' Phoma nebulosa'' * '' Phoma oncidii-sphacelati'' * '' Phoma scabra'' * '' Phoma sclerotioides'' * '' Phoma strasseri'' * '' Phoma tracheiphila''

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. * * {{Authority control Dothideomycetes genera Fungal plant pathogens and diseases Lichenicolous fungi Taxa described in 1880 Taxa named by Pier Andrea Saccardo