Waitea circinata
Encyclopedia
Waitea circinata is a species
of fungus
in the family
Corticiaceae
. Basidiocarps (fruit bodies) are thin, effused, and web-like, but the fungus is more frequently encountered in its similar but sterile anamorphic state, sometimes called Rhizoctonia zeae. Waitea circinata is best known as a plant pathogen, causing commercially significant damage to cereal
crops and turf grass.
field. The new genus
Waitea
, named after the Waite Agricultural Research Institute in Adelaide
, was created to accommodate the species. Because of its morphological similarity to species of Rhizoctonia
and Thanatephorus, Waitea circinata was presumed to belong within the Ceratobasidiaceae
, but cladistic analysis of DNA sequences has shown that it actually belongs in the Corticiaceae
and is close to species of Laetisaria
(which are also grass pathogens).
The anamorphic species Rhizoctonia zeae, originally described as the causal agent of ear rot of maize
, is a synonym of Waitea circinata. Rhizoctonia oryzae has also been considered a synonym, but the name is not validly published and is of doubtful application (it has also been considered a synonym of Rhizoctonia solani
). The name Rhizoctonia circinata has been used for the anamorph of Waitea circinata, but is not validly published and appears to be a portmanteau error.
Molecular research has shown that Waitea circinata is divided into four genetically distinct clades and that representatives of these clades cause visibly different diseases. They have been considered varieties
of the species ("var. circinata", "var oryzae", "var. zeae", and one unnamed), but the named varieties have not been formally described or validly published.
, colourless, often irregular, 2.5-11 μm wide, without clamp connection
s. Basidia are often constricted about the middle, with four short sterigmata. Basidiospores are smooth, oblong to cylindrical, 8-12 by 3.5-5 μm, colourless to pale ochre. Sclerotia are pinkish orange to brown, 0.5–3 mm wide.
but is commonest in warmer climates, producing optimal growth at around 25-35°C.
crops and amenity turf grasses. These include ear rot, root rot, and stalk rot of maize
, sheath spot of rice
, and various leaf & sheath spots of turf grasses.
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...
of fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
in the family
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...
Corticiaceae
Corticiaceae
The Corticiaceae are a family of fungi in the order Corticiales. The family formerly included almost all the corticioid fungi, whether they were related or not, and as such was highly artificial...
. Basidiocarps (fruit bodies) are thin, effused, and web-like, but the fungus is more frequently encountered in its similar but sterile anamorphic state, sometimes called Rhizoctonia zeae. Waitea circinata is best known as a plant pathogen, causing commercially significant damage to cereal
Cereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...
crops and turf grass.
Taxonomy
Waitea circinata was originally described from Australia in 1962, where it was found growing on the undersides of clods of earth in a wheatWheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
field. The new genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Waitea
Waitea
Waitea is a genus of fungi in the family Corticiaceae. The genus contains two species found in Australia and Switzerland....
, named after the Waite Agricultural Research Institute in Adelaide
Adelaide
Adelaide is the capital city of South Australia and the fifth-largest city in Australia. Adelaide has an estimated population of more than 1.2 million...
, was created to accommodate the species. Because of its morphological similarity to species of Rhizoctonia
Rhizoctonia
Rhizoctonia is a genus of anamorphic fungi in the order Cantharellales. Species do not produce spores, but are composed of hyphae and sclerotia and are asexual states of fungi in the genus Thanatephorus. Rhizoctonia species are saprotrophic, but are also facultative plant pathogens, causing...
and Thanatephorus, Waitea circinata was presumed to belong within the Ceratobasidiaceae
Ceratobasidiaceae
The Ceratobasidiaceae are a family of fungi in the order Cantharellales. All species within the family have basidiocarps that are thin and effused. They have sometimes been included within the corticioid fungi or alternatively within the "heterobasidiomycetes". Species are saprotrophic, but some...
, but cladistic analysis of DNA sequences has shown that it actually belongs in the Corticiaceae
Corticiaceae
The Corticiaceae are a family of fungi in the order Corticiales. The family formerly included almost all the corticioid fungi, whether they were related or not, and as such was highly artificial...
and is close to species of Laetisaria
Laetisaria
Laetisaria is a genus of fungi in the family Corticiaceae. The genus has a widespread distribution and contains three species....
(which are also grass pathogens).
The anamorphic species Rhizoctonia zeae, originally described as the causal agent of ear rot of maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, is a synonym of Waitea circinata. Rhizoctonia oryzae has also been considered a synonym, but the name is not validly published and is of doubtful application (it has also been considered a synonym of Rhizoctonia solani
Rhizoctonia solani
Rhizoctonia solani is a plant pathogenic fungus with a wide host range and worldwide distribution. This plant pathogen was discovered more than 100 years ago. Rhizoctonia solani frequently exists as thread-like growth on plants or in culture. Asexual spores are not produced, only the sexual stage...
). The name Rhizoctonia circinata has been used for the anamorph of Waitea circinata, but is not validly published and appears to be a portmanteau error.
Molecular research has shown that Waitea circinata is divided into four genetically distinct clades and that representatives of these clades cause visibly different diseases. They have been considered varieties
Variety (biology)
In botanical nomenclature, variety is a taxonomic rank below that of species: as such, it gets a three-part infraspecific name....
of the species ("var. circinata", "var oryzae", "var. zeae", and one unnamed), but the named varieties have not been formally described or validly published.
Description
Basidiocarps are effused, thin, web-like, smooth, white to pale ochre. Hyphae are multinucleateCell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
, colourless, often irregular, 2.5-11 μm wide, without clamp connection
Clamp connection
A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...
s. Basidia are often constricted about the middle, with four short sterigmata. Basidiospores are smooth, oblong to cylindrical, 8-12 by 3.5-5 μm, colourless to pale ochre. Sclerotia are pinkish orange to brown, 0.5–3 mm wide.
Habitat and distribution
The species appears to be a soil saprotroph, principally associated with grasses, possibly always as a pathogen. Though first described from Australia, it has a cosmopolitan distributionCosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
but is commonest in warmer climates, producing optimal growth at around 25-35°C.
Economic importance
Waitea circinata is the causal agent of a range of diseases of cerealCereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...
crops and amenity turf grasses. These include ear rot, root rot, and stalk rot of maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, sheath spot of rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
, and various leaf & sheath spots of turf grasses.