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[[File:Glomeromycota-spores.jpg|thumb|Gigaspora margarita in association with Lotus corniculatus]]Glomeromycota (informally glomeromycetes) is 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. The majority of evidence shows that the Glomeromycota are dependent on land plants (Nostoc in the case of Geosiphon) 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. Arbuscular mycorrhizal (AM) fungi have generally been classified in the Zygomycota (Order Glomales), but they do not form the zygospores characteristic of zygomycota, and all ‘glomalean’ fungi form mutualistic symbioses. Recent molecular studies have suggested a separate phylum is appropriate for the AM fungi, the Glomeromycota.
 
The Glomeromycota are limited in number compared to other phyla of fungi. However, they make up for this lack of [[diversity]] by being among the most proliferant and widespread of all fungi. As far as we know all species of Glomeromycota form mutualistic relationships with plants, in the role of  [[Arbuscular Mycorrhizal Fungi]].
 
[[File:GlomusSpores.jpg|400px|thumb||]]
 
These fungi were considered to be members of the [[Zygomycota]] for many years, mainly because their hyphae lack septa and because their spores may superficially resemble zygospores. More recent genetic evidence shows that they are quite distinct from other fungi and definitely belong in a separate phylum. Paleontologists have suspected this for a long time. The fossil roots of plants known to be as old as 450 million years clearly contain the hyphae and spores of Glomeromycota, showing this group to be among the oldest of fungi. The right photograph shows hyphae and spores of a species of Glomus, collected from the [[soil]] surrounding the roots of a balsam poplar tree. Such structures are indistinguishable from those in the fossil record. [2]
 
 
[[File:Glomeromycota-spores.jpg|thumb|Gigaspora margarita in association with Birds-foot trefoil (Lotus corniculatus)]]
 
==''' Phylogeny '''==
Glomeromycota make up one of the seven different phyla of the true fungi kingdom. The six other phyla are named as [[Chytridiomycota]], Blastocladiomycota, Neocallimastigomycota, Microsporidia, [[Ascomycota]], and [[Basidiomycota]]. [4]
 
Glomermycota cosists of four orders-
 
'''Diversisporales'''-
 
'''Glomerales'''-
 
'''Archaeosporales'''-
 
'''Paraglomerales'''-
 
 
 
 


=='''Reproduction'''==
=='''Reproduction'''==
Traditionally, taxonomy of AM fungi has been based on characteristics of the relatively large (40 to 800 µm diameter) multinucleate spores. There is no evidence that the Glomeromycota reproduce sexually. Studies using molecular marker genes have detected little or no genetic recombination so it is assumed generally that the spores are formed asexually.
The Glomeromycota have generally coenocytic (occasionally sparsely septate) mycelia and reproduce asexually through blastic development of the hyphal tip to produce spores (Glomerospores) with diameters of 80–500 μm. In some, complex spores form within a terminal saccule.


[[File:GlomusSpores.jpg|200px|thumb|left|]]
The Glomeromycota reproduction via sporeulation. There is no evidence that the Glomeromycota are able reproduce sexually. Studies using molecular marker in their genes have detected little to no evidence of genetic recombination, so it is assumed that the spores are formed asexually.
 
No member of the Glomeromycota has ever been grown in the laboratory independently of its plant associate.It is still not known exactly what these fungi need as nutrients. [1]
 
 
=='''Symbiotic Relationship'''==
 
The Glomeromycota have symbiotic relationships with plants in which they inavade  and evidence suggests that glomeromycota depend on the carbon and energy provided by their partner plants to survive [1]. Glomeromycetes form arbuscular [[mycorrhizae]] with the roots of plants. These realtionships are vital for nutrient uptake of [[plant roots]] as more than 80% of plant species depend on glomeromycetes [5].
 
 
 
 
=='''Colonization'''==
=='''Colonization'''==
AM fungi are obligate symbionts and none of these fungi has been cultivated without their plant hosts. Pure fungal biomass can be obtained only from cultures in transformed plant roots that can be cultivated in tissue culture, but only a small number of AM species are available in this form. Most samples can be contaminated by numerous other microorganisms, including fungi from other phyla, so progress with multigene phylogenies has been slow and the nuclear-encoded ribosomal RNA genes have remained the only widely accessible molecular markers.  
New colonization of arbuscular microrhysal fungi largely depends on the amount of inoculum present in the soil.
Although pre-existing hyphae and infected root fragments have been shown to successfully colonize the roots of a host, germinating spores are considered to be the key players in new host establishment. Spores are commonly dispersed by fungal and plant burrowing herbivore partners, but some exhibiting air dispersal capabilities are also known to exist. [3]
Studies have shown that spore germination is specific to particular environmental conditions such as right amount of nutrients, temperature or host availability. It has also been observed that the rate of root system colonization is directly proportional to spore density in the soil.In addition, new data also suggests that arbuscular microrhysal fungi host plants also secrete chemical which factor in the attraction of the fungi and enhance the growth of developing spore hyphae towards the root system. [3]
 
 
 
=='''References'''==
[1] Moore, D., Robson, G., Trinci, A. "21st Century Guidebook to Fungi", Cambridge University Press, 2020
 
[2]"A new fungal phylum, the Glomeromycota: phylogeny and evolution". Mycol. Res.
 
[3]Zangaro, Waldemar, Leila Rostirola, Vergal Souza, Priscila Almeida Alves, Bochi Lescano, Ricardo Rondina, Luiz Nogueira, and Eduardo Carrenho. "Root Colonization and Spore Abundance of Arbuscular Mycorrhizal Fungi in Distinct Successional Stages from an Atlantic Rainforest Biome in Southern Brazil." Mycorrhiza 2013.


Yet, in ecological terms, this is possibly the most important group of fungi because AM fungi form endomycorrhizal associations with about 80% of land plants. The association is essential for plant ecosystem function because the plants depend on it for their mineral nutrient uptake, which is efficiently performed by the mycelium of the fungal symbionts that extends outside the roots. Within root cells AM fungi form hyphal coils or the typical tree-like structures, the arbuscules.
[4]Augustyn, A. Managing Editor, Britannica, "Outline of Classification of Fungi"


Some also produce storage organs, termed vesicles (hence, another frequently used name for them – vesicular-arbuscular mycorrhizas or VAM-fungi). In phylogenetic terms they are important because they are the oldest unambiguous fungi known from the fossil record (see the Fossil Fungi section in Chapter 2). Put these two facts together and you get the suggestion that early colonisation of the land surface on Earth was promoted by the success of this plant-fungal symbiosis.
[5] Coleman, D., Callaham, M., Crossley, D. Jr.. "Fundamentals of Soil [[Ecology]]", Academic Press, 20th October, 2017.

Latest revision as of 13:02, 6 May 2022

The Glomeromycota are limited in number compared to other phyla of fungi. However, they make up for this lack of diversity by being among the most proliferant and widespread of all fungi. As far as we know all species of Glomeromycota form mutualistic relationships with plants, in the role of Arbuscular Mycorrhizal Fungi.

GlomusSpores.jpg

These fungi were considered to be members of the Zygomycota for many years, mainly because their hyphae lack septa and because their spores may superficially resemble zygospores. More recent genetic evidence shows that they are quite distinct from other fungi and definitely belong in a separate phylum. Paleontologists have suspected this for a long time. The fossil roots of plants known to be as old as 450 million years clearly contain the hyphae and spores of Glomeromycota, showing this group to be among the oldest of fungi. The right photograph shows hyphae and spores of a species of Glomus, collected from the soil surrounding the roots of a balsam poplar tree. Such structures are indistinguishable from those in the fossil record. [2]


Gigaspora margarita in association with Birds-foot trefoil (Lotus corniculatus)

Phylogeny

Glomeromycota make up one of the seven different phyla of the true fungi kingdom. The six other phyla are named as Chytridiomycota, Blastocladiomycota, Neocallimastigomycota, Microsporidia, Ascomycota, and Basidiomycota. [4]

Glomermycota cosists of four orders-

Diversisporales-

Glomerales-

Archaeosporales-

Paraglomerales-

   


Reproduction

The Glomeromycota reproduction via sporeulation. There is no evidence that the Glomeromycota are able reproduce sexually. Studies using molecular marker in their genes have detected little to no evidence of genetic recombination, so it is assumed that the spores are formed asexually.

No member of the Glomeromycota has ever been grown in the laboratory independently of its plant associate.It is still not known exactly what these fungi need as nutrients. [1]


Symbiotic Relationship

The Glomeromycota have symbiotic relationships with plants in which they inavade and evidence suggests that glomeromycota depend on the carbon and energy provided by their partner plants to survive [1]. Glomeromycetes form arbuscular mycorrhizae with the roots of plants. These realtionships are vital for nutrient uptake of plant roots as more than 80% of plant species depend on glomeromycetes [5].



Colonization

New colonization of arbuscular microrhysal fungi largely depends on the amount of inoculum present in the soil. Although pre-existing hyphae and infected root fragments have been shown to successfully colonize the roots of a host, germinating spores are considered to be the key players in new host establishment. Spores are commonly dispersed by fungal and plant burrowing herbivore partners, but some exhibiting air dispersal capabilities are also known to exist. [3] Studies have shown that spore germination is specific to particular environmental conditions such as right amount of nutrients, temperature or host availability. It has also been observed that the rate of root system colonization is directly proportional to spore density in the soil.In addition, new data also suggests that arbuscular microrhysal fungi host plants also secrete chemical which factor in the attraction of the fungi and enhance the growth of developing spore hyphae towards the root system. [3]


References

[1] Moore, D., Robson, G., Trinci, A. "21st Century Guidebook to Fungi", Cambridge University Press, 2020

[2]"A new fungal phylum, the Glomeromycota: phylogeny and evolution". Mycol. Res.

[3]Zangaro, Waldemar, Leila Rostirola, Vergal Souza, Priscila Almeida Alves, Bochi Lescano, Ricardo Rondina, Luiz Nogueira, and Eduardo Carrenho. "Root Colonization and Spore Abundance of Arbuscular Mycorrhizal Fungi in Distinct Successional Stages from an Atlantic Rainforest Biome in Southern Brazil." Mycorrhiza 2013.

[4]Augustyn, A. Managing Editor, Britannica, "Outline of Classification of Fungi"

[5] Coleman, D., Callaham, M., Crossley, D. Jr.. "Fundamentals of Soil Ecology", Academic Press, 20th October, 2017.

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