''Rhizophagus irregularis'' (previously known as ''Glomus intraradices'') is an

arbuscular mycorrhiza An arbuscular mycorrhiza (AM) (plural ''mycorrhizae'') is a type of mycorrhiza in which the symbiont fungus (''Arbuscular mycorrhizal fungi'', or AMF) penetrates the cortical cells of the roots of a vascular plant forming arbuscules. Arbuscul ...

l fungus used as a

soil inoculant Microbial inoculants, also known as soil inoculants or bioinoculants, are agricultural amendments that use beneficial rhizosphericic or endophytic microbes to promote plant health. Many of the microbes involved form symbiotic relationships with t ...

agriculture Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...

and

horticulture Horticulture (from ) is the art and science of growing fruits, vegetables, flowers, trees, shrubs and ornamental plants. Horticulture is commonly associated with the more professional and technical aspects of plant cultivation on a smaller and mo ...

. ''Rhizophagus irregularis'' is also commonly used in scientific studies of the effects of arbuscular mycorrhizal fungi on plant and soil improvement. Until 2001, the species was known and widely marketed as ''Glomus intraradices'', but molecular analysis of ribosomal DNA led to the reclassification of all arbuscular fungi from Zygomycota phylum to the Glomeromycota phylum.

Description

Spores

*Color — white, cream, yellow-brown Morton, J, & R Amarasinghe. ''Glomus intraradices''.''International Culture Collection of (Vesicular) Arbuscular Mycorrhizal Fungi''. 2006. West Virginia University. 17 November 2009. http://invam.caf.wvu.edu/index.html . *Shape — elliptical with irregularities *Size — generally between 40–140 μm

Hyphae

*Shape — Cylindrical or slightly flared *Size — Width: 11–18 μm

Identification

''Rhizophagus irregularis'' colonization peaks earlier than many of the other fungi in ''Rhizophagus''. There tends to be extensive hyphal networking and intense intraradical spores associated with older roots of host plants. At times the spores are densely clustered or patchily distributed, depending on the host species. When the spores are heavily clustered, mycorrhizologists and others will tend to mistake ''R. irregularis'' for ''G. fasciculatum''.

Reproduction

Rhizophagus irregularis (previously known as Glomus intraradices) has been found to colonise new plants by means of spores, hyphae or fragments of roots colonized by the fungus

Meiosis and recombination

Arbuscular mycorrhiza An arbuscular mycorrhiza (AM) (plural ''mycorrhizae'') is a type of mycorrhiza in which the symbiont fungus (''Arbuscular mycorrhizal fungi'', or AMF) penetrates the cortical cells of the roots of a vascular plant forming arbuscules. Arbuscul ...

(AM) fungi were thought to have propagated clonally for over 500 million years because of their lack of visible sexual structures and thus were considered to be an ancient

asexual Asexual or Asexuals may refer to: *Asexual reproduction **Asexual reproduction in starfish *Asexuality, the lack of sexual attraction to anyone or lack of interest in or desire for sexual activity. **Gray asexuality, the spectrum between asexualit ...

lineage. However,

homologs Homologous chromosomes or homologs are a set of one maternal and one paternal chromosome that pair up with each other inside a cell during meiosis. Homologs have the same genes in the same loci, where they provide points along each chromosome th ...

of 51

meiotic Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one copy ...

genes, including seven genes specific for meiosis were found to be conserved in the genomes of five AM species including ''Rhizophagus irregularis'' (referred to by its synonym designation ''Glomus irregulare''). This observation suggests that the supposedly ancient asexual AM fungi are likely capable of undergoing a conventional meiosis. ''R. irregularis''

dikaryon The dikaryon (karyogamy) is a cell nucleus feature that is unique to certain fungi. (The green alga '' Derbesia'' had been long considered an exception, until the heterokaryotic hypothesis was challenged by later studies.) Compatible cell-types c ...

s also appear to be capable of

genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryot ...

Ecology and distribution

Distribution

''Rhizophagus irregularis'' can be found in almost all soils, especially those populated with common host plants and in forests and grasslands. This is a brief list of some common host plants. Most agricultural crops will benefit from ''Rhizophagus irregularis'' inoculation. Generally host plants must be vascular plants, but not always. *Onion — ''

Allium cepa An onion (''Allium cepa'' , from Latin ), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onion which was classified ...

'' L. *Soapbush Wattle — ''

Acacia holosericea ''Acacia'', commonly known as wattles or acacias, is a genus of about of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa, South America, and Australa ...

'' *Flax — ''

Linum usitatissimum Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. In 2022, France produced 75% of the ...

'' L. *Cowpea — ''

Vigna unguiculata The cowpea (''Vigna unguiculata'') is an Annual plant, annual Herbaceous plant, herbaceous legume from the genus ''Vigna''. Its tolerance for sandy soil and low rainfall have made it an important crop in the Semi-arid climate, semiarid regions a ...

'' *Tomato Plant — ''

Lycopersicon esculentum The tomato (, ), ''Solanum lycopersicum'', is a plant whose fruit is an edible berry that is eaten as a vegetable. The tomato is a member of the nightshade family that includes tobacco, potato, and chili peppers. It originated from and was d ...

'' *Albaida — ''

Anthyllis cytisoides ''Anthyllis cytisoides'' is a summer-deciduous shrub of Southern Europe, common in the Balearic Islands and the southeastern coast of the Iberian Peninsula The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europ ...

Conservation and status

''Rhizophagus irregularis'' is not of conservation concern; however, individual populations could be harmed by agricultural chemicals and tillage.

Relevance

In numerous scientific studies ''R. irregularis'' has been shown to increase phosphorus uptake in multiple plants as well as improve soil aggregation due to hyphae. Because of these qualities, ''R. irregularis'' is commonly found in mycorrhizal based fertilizers. In a 2005 study, ''R. irregularis'' was found to be the only

l fungi that was able to control nutrient uptake amounts by individual hyphae depending on differing phosphorus levels in the surrounding soil.

References

External links

*
JGI Mycorrhizal Genomics Initiative on Rhizophagus irregularis DAOM 181602 v1.0
{{Authority control Soil biology Glomerales Fungi described in 1982 Fungus species