Dothideomycetes
Encyclopedia
Dothideomycetes is the largest and most diverse class
of ascomycete fungi. It comprises 11 orders
90 families
, 1300 genera
and over 19,000 known species
. Traditionally, most of its members were included in the loculoascomycetes, which is not part of the currently accepted classification. This indicates that several traditional morphological features in the class are not unique and DNA sequence comparisons are important to define the class.
The designation loculoascomycetes was first proposed for all fungi which have ascolocular development. This type of development refers to the way in which the sexual structure, bearing the sexual spores (ascospore
s) forms. Dothideomycetes mostly produce flask-like structures referred to as pseudothecia, although other shape variations do exist (e.g. see structures found in Hysteriales
). During ascolocular development pockets (locules) form first within the vegetative cells of the fungus and then all the subsequent structures form. These include the asci
which, superficially, have a thicker outer layer through which a thinner inner layer ‘bursts’, like a jack-in-a-box to release the spores. These asci are therefore referred to as bitunicate (superficially, two layers) or fissitunicate (referring to spore release). After several DNA sequence comparisons it is now clear that another group of fungi which share these characteristics are distantly related. These are the "black yeasts" in subclass Chaetothyriomycetidae (Eurotiomycetes
). This means that loculoascomycetes did not constitute a natural group
.
The best known members of this class are several important plant pathogens
(like Phaeosphaeria nodorum
and Venturia inaequalis
). However, a majority of described species are either found as endophyte
s or saprobes
growing on woody debris, decaying leaves or dung
. A smaller number exist as lichen
s and a single species, Cenococcum geophilum, can form mycorrhiza
l associations with plant roots.
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
of ascomycete fungi. It comprises 11 orders
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
90 families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, 1300 genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
and over 19,000 known species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
. Traditionally, most of its members were included in the loculoascomycetes, which is not part of the currently accepted classification. This indicates that several traditional morphological features in the class are not unique and DNA sequence comparisons are important to define the class.
The designation loculoascomycetes was first proposed for all fungi which have ascolocular development. This type of development refers to the way in which the sexual structure, bearing the sexual spores (ascospore
Ascospore
An ascospore is a spore contained in an ascus or that was produced inside an ascus. This kind of spore is specific to fungi classified as ascomycetes ....
s) forms. Dothideomycetes mostly produce flask-like structures referred to as pseudothecia, although other shape variations do exist (e.g. see structures found in Hysteriales
Hysteriales
The Hysteriales is an order of fungi in the class Dothideomycetes, subclass Pleosporomycetidae. It consists of a single family, Hysteriaceae. Members of Hysteriales produce elongated, often boat shaped sexual structures with slit-like openings . However species with these structures are very diverse...
). During ascolocular development pockets (locules) form first within the vegetative cells of the fungus and then all the subsequent structures form. These include the asci
Ascus
An ascus is the sexual spore-bearing cell produced in ascomycete fungi. On average, asci normally contain eight ascospores, produced by a meiotic cell division followed, in most species, by a mitotic cell division. However, asci in some genera or species can number one , two, four, or multiples...
which, superficially, have a thicker outer layer through which a thinner inner layer ‘bursts’, like a jack-in-a-box to release the spores. These asci are therefore referred to as bitunicate (superficially, two layers) or fissitunicate (referring to spore release). After several DNA sequence comparisons it is now clear that another group of fungi which share these characteristics are distantly related. These are the "black yeasts" in subclass Chaetothyriomycetidae (Eurotiomycetes
Eurotiomycetes
The Eurotiomycetes is a class of ascomycetes within the subphylum Pezizomycotina.Some members of the Eurotiomycetes were previously grouped in the class Plectomycetes.-Nomenclature:...
). This means that loculoascomycetes did not constitute a natural group
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
.
The best known members of this class are several important plant pathogens
Phytopathology
Plant pathology is the scientific study of plant diseases caused by pathogens and environmental conditions . Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants...
(like Phaeosphaeria nodorum
Phaeosphaeria nodorum
Phaeosphaeria nodorum is a major fungal pathogen of wheat and a member of the Dothideomycetes, a large fungal taxon that includes many important plant pathogens affecting all major crop plant families....
and Venturia inaequalis
Venturia inaequalis
Venturia inaequalis is an ascomycete fungus that causes the Apple scab disease.-Systematics:Venturia inaequalis anamorphs have been described under the names Fusicladium dendriticum and Spilocaea pomi. Whether V. inaequalis is a single species or contains several cryptic species has been a matter...
). However, a majority of described species are either found as endophyte
Endophyte
An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life without causing apparent disease. Endophytes are ubiquitous and have been found in all the species of plants studied to date; however, most of these endophyte/plant relationships...
s or saprobes
Detritivore
Detritivores, also known as detritophages or detritus feeders or detritus eaters or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles...
growing on woody debris, decaying leaves or dung
Coprophilous fungi
Coprophilous fungi are a type of saprobic fungi that grow on animal dung. The hardy spores of coprophilous species are unwittingly consumed by herbivores from vegetation, and are excreted along with the plant matter...
. A smaller number exist as lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
s and a single species, Cenococcum geophilum, can form mycorrhiza
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
l associations with plant roots.