Rhizophagus irregularis

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Rhizophagus irregularis
Reseau de mycorhize a l'interieur d'une racine.tif
mycorrhized roots of Vicia faba with Rhizophagus irregularis
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Glomeromycota
Class: Glomeromycetes
Order: Glomerales
Family: Glomeraceae
Genus: Rhizophagus
Species:
R. irregularis
Binomial name
Rhizophagus irregularis
(Błaszk., Wubet, Renker & Buscot) C. Walker & A. Schüßler 2010 [1]
Synonyms [2]
  • Glomus irregulareBłaszk., Wubet, Renker & Buscot, (2009)
  • Rhizoglomus irregulare(Błaszk., Wubet, Renker & Buscot) Sieverd., G.A. Silva & Oehl (2015)
  • Rhizophagus irregulare(Blaszk., Wubet, Renker & Buscot) C. Walker & A. Schüßler (2010)

Rhizophagus irregularis (previously known as Glomus intraradices [3] [4] ) is an arbuscular mycorrhizal fungus used as a soil inoculant in agriculture and horticulture. 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. [5]

Contents

Description

Spores

Hyphae

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. [6]

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 [7]

Meiosis and recombination

Arbuscular mycorrhiza (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 lineage. [8] However, homologs of 51 meiotic 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). [8] This observation suggests that the supposedly ancient asexual AM fungi are likely capable of undergoing a conventional meiosis. [8] R. irregularis dikaryons also appear to be capable of genetic recombination. [9]

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. [10]

Conservation and status

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

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. [17]

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 arbuscular mycorrhizal fungi that was able to control nutrient uptake amounts by individual hyphae depending on differing phosphorus levels in the surrounding soil. [13]

Related Research Articles

<span class="mw-page-title-main">Mycorrhiza</span> Fungus-plant symbiotic association

A mycorrhiza is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant's rhizosphere, its root system. Mycorrhizae play important roles in plant nutrition, soil biology, and soil chemistry.

<i>Medicago truncatula</i> Species of legume

Medicago truncatula, the barrelclover, strong-spined medick, barrel medic, or barrel medick, is a small annual legume native to the Mediterranean region that is used in genomic research. It is a low-growing, clover-like plant 10–60 centimetres (3.9–23.6 in) tall with trifoliate leaves. Each leaflet is rounded, 1–2 centimetres (0.39–0.79 in) long, often with a dark spot in the center. The flowers are yellow, produced singly or in a small inflorescence of two to five together; the fruit is a small, spiny pod.

<span class="mw-page-title-main">Arbuscular mycorrhiza</span> Symbiotic penetrative association between a fungus and the roots of a vascular plant

An arbuscular mycorrhiza (AM) is a type of mycorrhiza in which the symbiont fungus penetrates the cortical cells of the roots of a vascular plant forming arbuscules. Arbuscular mycorrhiza is a type of endomycorrhiza along with ericoid mycorrhiza and orchid mycorrhiza. They are characterized by the formation of unique tree-like structures, the arbuscules. In addition, globular storage structures called vesicles are often encountered.

<span class="mw-page-title-main">Glomeromycota</span> Phylum of fungi

Glomeromycota are one of eight currently recognized divisions within the kingdom Fungi, with approximately 230 described species. Members of the Glomeromycota form arbuscular mycorrhizas (AMs) with the thalli of bryophytes and the roots of vascular land plants. Not all species have been shown to form AMs, and one, Geosiphon pyriformis, is known not to do so. Instead, it forms an endocytobiotic association with Nostoc cyanobacteria. The majority of evidence shows that the Glomeromycota are dependent on land plants for carbon and energy, but there is recent circumstantial evidence that some species may be able to lead an independent existence. The arbuscular mycorrhizal species are terrestrial and widely distributed in soils worldwide where they form symbioses with the roots of the majority of plant species (>80%). They can also be found in wetlands, including salt-marshes, and associated with epiphytic plants.

Glomus aggregatum is an arbuscular mycorrhizal fungus used as a soil inoculant in agriculture and horticulture. Like other species in this phylum it forms obligate symbioses with plant roots, where it obtains carbon (photosynthate) from the host plant in exchange for nutrients and other benefits.

<i>Glomus</i> (fungus) Genus of arbuscular mycorrhizal fungi

Glomus is a genus of arbuscular mycorrhizal (AM) fungi, and all species form symbiotic relationships (mycorrhizae) with plant roots. Glomus is the largest genus of AM fungi, with ca. 85 species described, but is currently defined as non-monophyletic.

<span class="mw-page-title-main">Glomerales</span> Order of fungi

Glomerales is an order of symbiotic fungi within the phylum Glomeromycota.

<span class="mw-page-title-main">Mucoromycotina</span> Subphylum of fungi

Mucoromycotina is a subphylum of uncertain placement in Fungi. It was considered part of the phylum Zygomycota, but recent phylogenetic studies have shown that it was polyphyletic and thus split into several groups, it is now thought to be a paraphyletic grouping. Mucoromycotina is currently composed of 3 orders, 61 genera, and 325 species. Some common characteristics seen throughout the species include: development of coenocytic mycelium, saprotrophic lifestyles, and filamentous.

The Diversisporaceae are a family of fungi in the order Diversisporales. These fungi form arbuscular mycorrhiza and vesicles in roots.

The mycorrhizosphere is the region around a mycorrhizal fungus in which nutrients released from the fungus increase the microbial population and its activities. The roots of most terrestrial plants, including most crop plants and almost all woody plants, are colonized by mycorrhiza-forming symbiotic fungi. In this relationship, the plant roots are infected by a fungus, but the rest of the fungal mycelium continues to grow through the soil, digesting and absorbing nutrients and water and sharing these with its plant host. The fungus in turn benefits by receiving photosynthetic sugars from its host. The mycorrhizosphere consists of roots, hyphae of the directly connected mycorrhizal fungi, associated microorganisms, and the soil in their direct influence.

<span class="mw-page-title-main">Ectomycorrhiza</span> Non-penetrative symbiotic association between a fungus and the roots of a vascular plant

An ectomycorrhiza is a form of symbiotic relationship that occurs between a fungal symbiont, or mycobiont, and the roots of various plant species. The mycobiont is often from the phyla Basidiomycota and Ascomycota, and more rarely from the Zygomycota. Ectomycorrhizas form on the roots of around 2% of plant species, usually woody plants, including species from the birch, dipterocarp, myrtle, beech, willow, pine and rose families. Research on ectomycorrhizas is increasingly important in areas such as ecosystem management and restoration, forestry and agriculture.

<i>Rhizophagus</i> (fungus) Genus of fungi

Rhizophagus is a genus of arbuscular mycorrhizal (AM) fungi that form symbiotic relationships (mycorrhizas) with plant roots. The genome of Rhizophagus irregularis was recently sequenced.

Orchid mycorrhizae are endomycorrhizal fungi which develop symbiotic relationships with the roots and seeds of plants of the family Orchidaceae. Nearly all orchids are myco-heterotrophic at some point in their life cycle. Orchid mycorrhizae are critically important during orchid germination, as an orchid seed has virtually no energy reserve and obtains its carbon from the fungal symbiont.

<span class="mw-page-title-main">Mycorrhiza helper bacteria</span> Group of organisms

Mycorrhiza helper bacteria (MHB) are a group of organisms that form symbiotic associations with both ectomycorrhiza and arbuscular mycorrhiza. MHBs are diverse and belong to a wide variety of bacterial phyla including both Gram-negative and Gram-positive bacteria. Some of the most common MHBs observed in studies belong to the phylas Pseudomonas and Streptomyces. MHBs have been seen to have extremely specific interactions with their fungal hosts at times, but this specificity is lost with plants. MHBs enhance mycorrhizal function, growth, nutrient uptake to the fungus and plant, improve soil conductance, aid against certain pathogens, and help promote defense mechanisms. These bacteria are naturally present in the soil, and form these complex interactions with fungi as plant root development starts to take shape. The mechanisms through which these interactions take shape are not well-understood and needs further study.

Dr. Mohamed Hijri is a biologist who studies arbuscular mycorrhizal fungi (AMF). He is a professor of biology and research at the Institut de recherche en biologie végétale at the University of Montreal.

<span class="mw-page-title-main">Mucoromycota</span> Diverse group of molds

Mucoromycota is a division within the kingdom fungi. It includes a diverse group of various molds, including the common bread molds Mucor and Rhizopus. It is a sister phylum to Dikarya.

<i>Funneliformis mosseae</i> Species of fungus

Funneliformis mosseae is a species of fungus in the family Glomeraceae, which is an arbuscular mycorrhizal (AM) fungi that forms symbiotic relationships with plant roots. Funneliformis mosseae has a wide distribution worldwide, and can be found in North America, South America, Europe, Africa, Asia and Australia. Funneliformis are characterized by having an easily visible septum in the area of the spore base and are often cylindrical or funnel-shaped. Funneliformis mosseae similarly resembles Glomus caledonium, however the spore wall of Funneliformis mosseae contains three layers, whereas Gl. caledonium spore walls are composed of four layers. Funneliformis is an easily cultivated species which multiplies well in trap culture, along with its high distribution, F. mosseae is not considered endangered and is often used for experimental purposes when combined with another host.

Rhizophagus clarus is an arbuscular mycorrhizal fungus in the family Glomeraceae. The species has been shown to improve nutrient absorption and growth in several agricultural crops but is not typically applied commercially.

The International Collection of (Vesicular) Arbuscular Mycorrhizal Fungi (INVAM) is the largest collection of living arbuscular mycorrhizal fungi (AMF) and includes Glomeromycotan species from 6 continents. Curators of INVAM acquire, grow, identify, and elucidate the biology, taxonomy, and ecology of a diversity AMF with the mission to expand availability and knowledge of these symbiotic fungi. Culturing AMF presents difficulty as these fungi are obligate biotrophs that must complete their life cycle while in association with their plant hosts, while resting spores outside of the host are vulnerable to predation and degradation. Curators of INVAM have thus developed methods to overcome these challenges to increase the availability of AMF spores. The inception of this living collection of germplasm occurred in the 1980s and it takes the form of fungi growing in association with plant symbionts in the greenhouse, with spores preserved in cold storage within their associated rhizosphere. AMF spores acquired from INVAM have been used extensively in both basic and applied research projects in the fields of ecology, evolutionary biology, agroecology, and in restoration. INVAM is umbrellaed under the Kansas Biological Survey at The University of Kansas, an R1 Research Institution. The Kansas Biological Survey is also home to the well-known organization Monarch Watch. INVAM is currently located within the tallgrass prairie ecoregion, and many collaborators and researchers associated with INVAM study the role of AMF in the mediation of prairie biodiversity. James Bever and Peggy Schultz are the Curator and Director of Operation team, with Elizabeth Koziol and Terra Lubin as Associate Curators.

<i>Glomus macrocarpum</i> Species of fungus

Glomus macrocarpum is a vesicular-arbuscular endomycorrhizal plant pathogen in the Glomeraceae family of fungi. Also occasionally known as Endogone macrocarpa, G. macrocarpum is pathogenic to multiple plants, including tobacco and chili plants. G. macrocarpum was first discovered in the French woodlands by the Tulsane brothers in the early to mid 1800s. Their first known description of G. macrocarpum was published in the New Italian Botanical Journal in 1845. G. macrocarpum has since been documented in over 26 countries, including Australia, China, and Japan for example. G. macrocarpum is frequently found in grassy meadows, forests, greenhouses, and fruit orchards. It is known for its small, round-edged, and light brown to yellow-brown sporocarp. G. macrocarpum is sometimes known as the Glomerales truffle.

References

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  2. "Rhizophagus irregularis". MycoBank. Retrieved 30 April 2019.
  3. "Home — Rhizophagus irregularis DAOM 181602 v1.0". genome.jgi.doe.gov.
  4. Stockinger, H.; Walker, C.; Schußler, A. (2009). "'Glomus intraradices DAOM197198', a model fungus in arbuscular mycorrhiza research, is not Glomus intraradices". New Phytol. 183 (4): 1176–87. doi: 10.1111/j.1469-8137.2009.02874.x . PMID   19496945.
  5. Krüger, Manuela; Claudia Krüger; Christopher Walker; Herbert Stockinger; Arthur Schüßler (2012). "Phylogenetic reference data for systematics and phylotaxonomy of arbuscular mycorrhizal fungi from phylum to species level". New Phytologist. 193 (4): 970–984. doi:10.1111/j.1469-8137.2011.03962.x. PMID   22150759.
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