Mycorrhizas are symbiotic associations between fungi in the soil and the roots of plants. Several types exist, each of which is defined by their morphological characteristics at the interface between the plant and fungus, as well as the identity of both fungal and plant partners. Mycorrhizas are the most ubiquitous terrestrial symbiosis in nature and are believed to have played an integral role in helping plants transition from aquatic to terrestrial environments c. 400 million years before present. The most recognised function of the symbiosis is the bidirectional exchange of plant growth limiting soil nutrients from the fungal partner(s) for photosynthetically derived sugars from the plant host(s). However, the function of mycorrhizal fungi extends beyond nutrient exchange, as they play other important roles for their hosts including increased resistance to pathogens and herbivory and improved plant–water relations.

Key Concepts

  • Mycorrhiza refers to the symbiotic relationship between a fungus in the soil and the root of a plant.
  • The mycorrhizal symbiosis is the most widely distributed symbiosis on earth.
  • Mycorrhizas are classified into different types, each of which is defined by the identity of plant and fungal partners, as well as the morphological structures, where the partners interface.
  • The mycorrhizal symbiosis while generally considered a mutualism where both partners benefit, can fall on a continuum from parasitism to mutualism, where the direction and strength of the interaction depend upon the identity of the partners and their environmental conditions.
  • Mycorrhizas are ubiquitous in nature, having strong influences on plant community ecology including diversity and productivity.

Keywords: fungi; symbiosis; Glomeromycotina; Basidiomycota; Ascomycota; plant–soil feedbacks; soil ecology

Figure 1. Diagrammatic representation of the two broad categories and six types of mycorrhiza found in nature and described in the text. Fungal tissues are shown in red, plant tissues in black. In each type the diagnostic fungal structures are shown, the nature and directions of the main nutrient movements are indicated, and the main groups of fungi and plants involved are listed. C, carbon (sugars); N, nitrogen; P, phosphorus; K, potassium; Zn, zinc. The sizes of the letters indicate the relative importance of the transfer process within the mycorrhizal type. Reproduced with permission from Read . © John Wiley and Sons.


Augé RM, Toler HD and Saxton AM (2015) Arbuscular mycorrhizal symbiosis alters stomatal conductance of host plants more under drought than under amply watered conditions: a meta‐analysis. Mycorrhiza 25 (1): 13–24.

Babikova Z, Gilbert L, Bruce Toby JA, et al. (2013) Underground Signals Carried through Common Mycelial Networks Warn Neighbouring Plants of Aphid Attack. Ecology Letters 16 (7): 835–843.

Besser A, Puech‐Pagè V, Kiefer P, et al. (2006) Strigolactones stimulate arbuscular mycorrhizal fungi by activating mitochondria. PLoS Biology 4: e226.

Brundrett M (1991) Mycorrhizas in natural ecosystems. Advances in Ecological Research 21: 171–313.

Cameron DD, Johnson I, Read DJ and Leake JR (2008) Giving and receiving: measuring the carbon cost of mycorrhizas in the green orchid, Goodyera repens. New Phytologist 180 (1): 176–184‐8137.2008.02533.x.

Chen ECH, Mathieu S, Hoffrichter A, et al. (2018) Single nucleus sequencing reveals evidence of inter‐nucleus recombination in arbuscular mycorrhizal fungi. eLife 7: e39813.

Corradi N and Brachmann A (2017) Fungal mating in the most widespread plant symbionts? Trends in Plant Science 22: 175–183.

Dickie IA, Bolstridge N, Cooper JA and Peltzer DA (2010) Co‐invasion by Pinus and its mycorrhizal fungi. New Phytologist 187: 475–484.

Duddridge JA, Malibari A and Read DJ (1980) Structure and function of mycorrhizal rhizomorphs with special reference to their role in water transport. Nature 287: 834–836.

Field KJ and Pressel S (2018) Unity in diversity: structural and functional insights into the ancient partnerships between plants and fungi. New Phytologist 220 (4): 996–1011. DOI: 10.1111/nph.15158.

Francis R and Read DJ (1984) Direct transfer of carbon between plants connected by vesicular–arbuscular mycorrhizal mycelium. Nature 307: 53–56.

Frank AB (1885) On the nutrient providing root‐symbiosis between underground fungi and certain trees. Berichte der Deutschen Botanischen Gesellschaft 5: 395–409 (in German).

Genney DR, Alexander IJ and Hartley SE (2000) Exclusion of grass roots from the soil organic layers by Calluna: the role of ericoid mycorrhizas. Journal of Experimental Botany 51: 1117–1125.

Hall IR, Yun W and Amicucci A (2003) Cultivation of edible ectomycorrhizal mushrooms. Trends in Biotechnology 21: 433–438.

van der Heijden MGA, Klironomos JN, Ursic M, et al. (1998) Mycorrhizal fungal diversity determines plant biodiversity ecosystem variability and productivity. Nature 396: 69–72.

van der Heijden MGA, Martin FM, Selosse MA and Sanders IR (2015) Mycorrhizal ecology and evolution: the past, the present, and the future. New Phytologist 205 (4): 1406–1423.

Hibbett DS and Matheny PB (2009) The relative ages of ectomycorrhizal mushrooms and their plant hosts estimatedusing Bayesian relaxed molecular clock analyses. BMC Biology 7: 13.

Hobbie EA (2006) Carbon allocation to ectomycorrhizal fungi correlates with below‐ground allocation in culture studies. Ecology 87: 563–569.

Hoysted GA, Kowal J, Jacob A, et al. (2018) A mycorrhizal revolution. Current Opinion in Plant Biology 44: 1–6. DOI: 10.1016/j.pbi.2017.12.004.

Hynson NA and Bruns TD (2010) Fungal hosts for mycoheterotrophic plants: a nonexclusive, but highly selective club. New Phytologist 185 (3): 598–601.

Ivanov S, Jotham A, Howard Berg R and Maria JH (2019) Extensive Membrane Systems at the Host‐arbuscular Mycorrhizal Fungus Interface. Nature Plants 5 (2): 194. DOI: 10.1038/s41477-019-0364-5.

Jacquemyn H and Merckx VSFT (2019) Mycorrhizal symbioses and the evolution of trophic modes in plants. Journal of Ecology. DOI: 10.1111/1365‐2745.13165.

Jakobsen I and Rosendahl L (1990) Carbon flow into soil and external hyphae from roots of mycorrhizal cucumber plants. New Phytologist 115: 77–83.

Johnson NC, Graham JH and Smith FA (1997) Functioning of mycorrhizal associations along the mutualism‐parasitism continuum. New Phytologist 135: 575–585.

Kohler A, Kuo A, Nagy LG, et al. (2015) Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists. Nature Genetics 47: 410–415.

Kolařík M and Vohník M (2018) When the ribosomoal DNA does not tell the truth: The case of the taxonomic position of Kurtia argillacea, an ericoid mycorrhizal fungus residing among Hymenochaetales. Fungal Biology 222 (1): 1–18.

Kühdorf K, Münzenberger B, Begerow D, Gómez‐Laurito J and Hüttl RF (2015) Leotia cf. lubrica forms arbutoid mycorrhiza with Comarostaphylis arbutoides (Ericaceae). Mycorrhiza 25: 109–120.

Lamhamedi MS, Godbout C and Fortin JA (1994) Dependence of Laccaria bicolor basidiome development on current photosynthesis of Pinus strobus seedlings. Canadian Journal of Forest Research 24: 1797–1804.

Leopold DR (2016) Ericoid fungal diversity: challenges and opportunities for mycorrhizal research. Fungal Ecology 24: 114–123.

LePage BA, Currah RS, Stockey RA and Rothwell GW (1997) Fossil ectomycorrhizae from the middle Eocene. American Journal of Botany 84: 410–412.

Luginbuehl LH, Menard GN, Kurup S, et al. (2017) Fatty acids in arbuscular mycorrhizal fungi are synthesized by the host plant. Science 356: 1175–1178.

Martin F, Kohler A, Murat C, Veneault‐Fourrey C and Hibbett DS (2016) Unearthing the roots of ectomycorrhizal symbioses. Nature Reviews Microbiology 14 (12): 760–773. DOI: 10.1038/nrmicro.2016.149.

Morton JB and Benny GL (1990) Revised classification of arbuscular mycorrhizal fungi (Zygomycetes): a new order, Glomales, two new suborders, Glomineae and Gigasporineae, and two new families, Acaulosporaceae and Gigasporaceae, with an emendation of Glomaceae. Mycotaxon 37: 471–491.

Mosse B (1973) Advances in the study of vesicular–arbuscular mycorrhizas. Annual Review of Phytopathology 11: 170–196.

Pearson V and Read D (1973) Biology of mycorrhiza in the Ericaceae II: transport of carbon and phosphorus by endophyte and mycorrhiza. New Phytologist 72: 1325–1331.

Perotto S, Girlanda M and Martino E (2002) Ericoid mycorrhizal fungi: some new perspective on old acquaintances. Plant and Soil 244: 41–53.

Read DJ (1983) The biology of mycorrhiza in the Ericales. Canadian Journal of Botany 61: 985–1004.

Read DJ (1996) The structure and function of the ericoid mycorrhizal root. Annals of Botany 77: 365–376.

Read DJ (2001) Mycorrhizal. In: eLS, John Wiley & Sons, Ltd: Chichester DOI: 10.1002/9780470015902.a0000372.pub2.

Redecker D, Kodner R and Graham LE (2000) Glomalean fungi from the Ordovician. Science 289: 1920–1921.

Redecker D, Schüβler A, Stockinger H, et al. (2013) An evidence‐based consensus for the classification of arbuscular mycorrhizal fungi (Glomeromycota). Mycorrhiza 23: 515–531.

Schiebold JMI, Bidartondo MI, Lenhard F, Makiola A and Gebauer G (2015) Exploiting mycorrhizas in broad daylight: partial mycoheterortrophy is a common nutritional strategy in meadow orchids. Journal of Ecology 106 (1): 168–178.

Schouteden N, De Waele D, Panis B and Vos CM (2015) Arbuscular mycorrhizal fungi for the biocontrol of plant‐parasitic nematodes: a review of the mechanisms involved. Frontiers in Microbiology 6: 1280. DOI: 10.3389/fmicb.2015.01280.

Schwery O, Onstein RE, Bouchenak‐Khelladi Y, et al. (2015) As old as the mountains: the radiations of the Ericaceae. New Phytologist 207: 355–367.

Sikes BA, Cottenie K and Klironomos JN (2009) Plant and fungal identity determines pathogen protection of plant roots by arbuscular mycorrhizas. Journal of Ecology 97: 1274–1280.

Simard SW, Perry DA, Jones MD, et al. (1997) Net transfer of carbon between ectomycorrhizal tree species in the field. Nature 388: 579–582.

Smith FA and Smith SE (1996) Mutualism and parasitism: diversity in function and structure in the ‘Arbuscular’ (VA) mycorrhizal symbiosis. Advances in Botanical Research 22: 1–43.

Smith SE and Read DJ (2008) Mycorrhizal Symbiosis, 3rd edn. Academic Press: London.

Spatafora JW, Chang Y, Benny GL, et al. (2016) A phylum‐level phylogenetic classification of zygomycete fungi based on genome‐scale data. Mycologia 108: 1028–1046.

Taylor DL and Bruns TD (1997) Independent, specialized invasions of ectomycorrhizal mutualism by two nonphotosynthetic orchids. Proceedings of the National Academy of Sciences of the USA 94: 4510–4515.

Tedersoo L, May TW and Smith ME (2010) Ectomycorrhizal lifestyle in fungi: global diversity, distribution, and evolution of phylogenetic lineages. Mycorrhiza 20 (4): 217–263.

Tedersoo L and Smith ME (2013) Lineages of ectomycorrhizal fungi revisited: foraging strategies and novel lineages revealed by sequences from belowground. Fungal Biology Reviews 27: 83–99.

Velmala SM, Vuorinen I, Ulimari A and Pennanen T (2018) Ectomycorrhizal fungi increase the vitality of Norway spruce seedlings under the pressure of Heterobasidion root rot in vitro but may increase susceptibility to foliar necrotrophs. Fungal Biology 122 (2–3): 101–109.

Wang B and Qiu YL (2006) Phylogenetic distribution and evolution of mycorrhizas in land plants. Mycorrhiza 16: 299–363.

Further Reading

Brundrett MC (2002) Coevolution of roots and mycorrhizas of land plants. New Phytologist 154 (2): 275–304.

van der Heijden MGA, Martin FM, Selosse MA and Sanders IR (2014) Mycorrhizal ecology and evolution: the past, the present, and the future. New Phytologist 205: 1406–1423.

Johnson NC, Graham JH and Smith FA (1997) Functioning of Mycorrhizal Associations along the Mutualism‐Parasitism Continuum. New Phytologist 135 (4): 575–585.

Kiers TE, Duhamel M, Beesetty Y, et al. (2011) Reciprocal rewards stabilize cooperation in the mycorrhizal Symbiosis. Science 333 (6044): 880–882.

Kivlin SN, Hawkes CV and Treseder KK (2011) Global diversity and distribution of arbuscular mycorrhizal fungi. Soil Biology and Biochemistry 43 (11): 2294–2303.

Peay KG, Kennedy PG and Bruns TD (2008) Fungal Community Ecology: a hybrid beast with a molecular master. Bioscience 58 (9): 799–810.

Rasmussen HN (1995) Terrestrial Orchids: From Seed to Mycotrophic Plant. Cambridge University Press: Cambridge.

Read DJ, Lewis DH, Fitter AH and Alexander IA (eds) (1992) Mycorrhizas in Ecosystems. CAB International: Wallingford.

Wang B and Qiu Y‐L (2006) Phylogenetic distribution and evolution of mycorrhizas in land plants. Mycorrhiza 16 (5): 299–363.

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Egan, Cameron P, and Hynson, Nicole A(Aug 2019) Mycorrhiza. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000372.pub2]