Epichloë
Encyclopedia
Epichloë species and their close relatives, the Neotyphodium
species, are systemic and constitutive symbionts of cool-season grasses (Poaceae
subfamily Pooideae
), and belong to the fungal family Clavicipitaceae
. Among the Clavicipitaceae
, many species are specialized to form and maintain systemic, constitutive (long-term) symbioses
with plants, often with limited or no disease incurred on the host. The best-studied of these symbionts are associated with the grass
es and sedges
, in which they infect the leaves and other aerial tissues by growing between the plant cells (endophytic
growth) or on the surface above or beneath the cuticle (epiphytic
growth). An individual infected plant will generally bear only a single genetic individual clavicipitaceous symbiont, so the plant-fungus system constitutes a genetic unit called a symbiotum (pl. symbiota).
Symptoms and signs of the fungal infection, if manifested at all, only occur on a specific tissue or site of the host tiller
, where the fungal stroma or sclerotium emerges. The stroma (pl. stromata) is a mycelial cushion that gives rise first to asexual spores (conidia
), then to the sexual fruiting bodies (ascocarp
s; perithecia). Sclerotia
are hard resting structures that later (after incubation on the ground) germinate to form stipate stromata. Depending on the fungus species, the host tissues on which stromata or sclerotia are produced may be young inflorescences and surrounding leaves, individual florets, nodes, or small segments of the leaves. Young stromata are hyaline (colorless), and as they mature they turn dark gray, black, or yellow-orange. Mature stromata eject meiotically derived spores (ascospore
s), which are ejected into the atmosphere and initiate new plant infections (horizontal transmission
). In some cases no stroma or sclerotium is produced, but the fungus infects seeds produced by the infected plant, and is thereby transmitted vertically
to the next host generation. Most Epichloë species and all of their asexual derivatives, the Neotyphodium
species, can vertically transmit.
Neotyphodium
species (with the likely exception of N. chilense) are closely related to teleomorphic species of the genus Epichloë, from which many have evolved by processes involving interspecific hybridization. Molecular phylogenetic evidence demonstrates that asexual Neotyphodium
species are derived either from individual Epichloë species, or more commonly, from hybrids with at least two ancestral Epichloë species. Like the Neotyphodium species, many species in Epichloë produce biologically active alkaloids, such as ergot alkaloids, indole-diterpenoids (e.g., lolitrem B), loline alkaloids
, and the unusual guanidinium alkaloid, peramine. Because of their close relationships and shared biological properties, members of these two genera are collectively called epichloae (singular = epichloë).
Neotyphodium
Neotyphodium is a form genus containing species of endophytic fungi. These endophytes are asexual, seed-borne symbionts of cool-season grasses, and grow intercellularly throughout the aerial tissues of their hosts, including shoot apical meristems, leaf sheaths and blades, inflorescences, seeds and...
species, are systemic and constitutive symbionts of cool-season grasses (Poaceae
Poaceae
The Poaceae is a large and nearly ubiquitous family of flowering plants. Members of this family are commonly called grasses, although the term "grass" is also applied to plants that are not in the Poaceae lineage, including the rushes and sedges...
subfamily Pooideae
Pooideae
The Pooideae is a subfamily of the true grass family Poaceae. It includes some major cereals such as wheat, barley, oat, rye and many lawn and pasture grasses.- List :...
), and belong to the fungal family Clavicipitaceae
Clavicipitaceae
Clavicipitaceae is a family of fungi within the order Hypocreales. It consists of 43 genera, and 321 species.-Phylogeny:Molecular phylogenetic analysis of multigene DNA sequence data indicates that the taxon, Clavicipitaceae, is paraphyletic, and consists of three well-defined clades, at least one...
. Among the Clavicipitaceae
Clavicipitaceae
Clavicipitaceae is a family of fungi within the order Hypocreales. It consists of 43 genera, and 321 species.-Phylogeny:Molecular phylogenetic analysis of multigene DNA sequence data indicates that the taxon, Clavicipitaceae, is paraphyletic, and consists of three well-defined clades, at least one...
, many species are specialized to form and maintain systemic, constitutive (long-term) symbioses
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
with plants, often with limited or no disease incurred on the host. The best-studied of these symbionts are associated with the grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es and sedges
Cyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...
, in which they infect the leaves and other aerial tissues by growing between the plant cells (endophytic
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...
growth) or on the surface above or beneath the cuticle (epiphytic
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
growth). An individual infected plant will generally bear only a single genetic individual clavicipitaceous symbiont, so the plant-fungus system constitutes a genetic unit called a symbiotum (pl. symbiota).
Symptoms and signs of the fungal infection, if manifested at all, only occur on a specific tissue or site of the host tiller
Tiller (botany)
A tiller is a stem produced by grass plants, and refers to all shoots that grow after the initial parent shoot grows from a seed. Tillers are segmented, each segment possessing its own two-part leaf...
, where the fungal stroma or sclerotium emerges. The stroma (pl. stromata) is a mycelial cushion that gives rise first to asexual spores (conidia
Conidium
Conidia, sometimes termed conidiospores, are asexual, non-motile spores of a fungus and are named after the greek word for dust, konia. They are also called mitospores due to the way they are generated through the cellular process of mitosis...
), then to the sexual fruiting bodies (ascocarp
Ascocarp
An ascocarp, or ascoma , is the fruiting body of an ascomycete fungus. It consists of very tightly interwoven hyphae and may contain millions of asci, each of which typically contains eight ascospores...
s; perithecia). Sclerotia
Sclerotium
A sclerotium is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant until a favorable opportunity for growth. Other fungi that produce...
are hard resting structures that later (after incubation on the ground) germinate to form stipate stromata. Depending on the fungus species, the host tissues on which stromata or sclerotia are produced may be young inflorescences and surrounding leaves, individual florets, nodes, or small segments of the leaves. Young stromata are hyaline (colorless), and as they mature they turn dark gray, black, or yellow-orange. Mature stromata eject meiotically derived 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), which are ejected into the atmosphere and initiate new plant infections (horizontal transmission
Horizontal transmission
Horizontal transmission is the transmission of a bacterial, fungal, or viral infection between members of the same species that are not in a parent-child relationship....
). In some cases no stroma or sclerotium is produced, but the fungus infects seeds produced by the infected plant, and is thereby transmitted vertically
Vertical transmission
Vertical transmission, also known as mother-to-child transmission, is the transmission of an infection or other disease from mother to child immediately before and after birth during the perinatal period. A pathogen's transmissibility refers to its capacity for vertical transmission...
to the next host generation. Most Epichloë species and all of their asexual derivatives, the Neotyphodium
Neotyphodium
Neotyphodium is a form genus containing species of endophytic fungi. These endophytes are asexual, seed-borne symbionts of cool-season grasses, and grow intercellularly throughout the aerial tissues of their hosts, including shoot apical meristems, leaf sheaths and blades, inflorescences, seeds and...
species, can vertically transmit.
Neotyphodium
Neotyphodium
Neotyphodium is a form genus containing species of endophytic fungi. These endophytes are asexual, seed-borne symbionts of cool-season grasses, and grow intercellularly throughout the aerial tissues of their hosts, including shoot apical meristems, leaf sheaths and blades, inflorescences, seeds and...
species (with the likely exception of N. chilense) are closely related to teleomorphic species of the genus Epichloë, from which many have evolved by processes involving interspecific hybridization. Molecular phylogenetic evidence demonstrates that asexual Neotyphodium
Neotyphodium
Neotyphodium is a form genus containing species of endophytic fungi. These endophytes are asexual, seed-borne symbionts of cool-season grasses, and grow intercellularly throughout the aerial tissues of their hosts, including shoot apical meristems, leaf sheaths and blades, inflorescences, seeds and...
species are derived either from individual Epichloë species, or more commonly, from hybrids with at least two ancestral Epichloë species. Like the Neotyphodium species, many species in Epichloë produce biologically active alkaloids, such as ergot alkaloids, indole-diterpenoids (e.g., lolitrem B), loline alkaloids
Loline alkaloids
A loline alkaloid is a member of the 1-aminopyrrolizidines , which are bioactive natural products with several distinct biological and chemical features...
, and the unusual guanidinium alkaloid, peramine. Because of their close relationships and shared biological properties, members of these two genera are collectively called epichloae (singular = epichloë).
Species
- Epichloë amarillans
- Epichloë baconii
- Epichloë brachyelytri
- Epichloë bromicola
- Epichloë clarkii
- Epichloë elymi
- Epichloë festucae
- Epichloë glyceriae
- Epichloë sylvatica
- Epichloë typhina
- Epichloë yangzii