Ectomycorrhizal fungi--fairy rings and the wood-wide web.

Ectomycorrhizal fungi – fairy rings and the wood-wide web Many of us will have seen fairy rings, the mysterious circles of fungal fruiting bodies that occur in open grassy places or in forests. The secrecy about these rings is expressed in their naming: in English folklore, the rings were said to be caused by fairies dancing in a circle (Fig. 1) whereas in German-speaking Europe they are known as 'Hexenringe', stemming from an old mediaeval belief that they represented places where witches would have their gatherings. An old belief says that if you run around a fairy ring nine times on the first night of the new moon, you will hear sounds of music and laughter coming up from the underground home of the elves. Unlike this sorcerous practice, Lian et al. (this issue; pp. 825– 836) used sturdy molecular techniques to provide insights into the below-ground fungal world of fairy rings formed by the ectomycorrhizal (ECM) basidiomycete Tricho-loma matsutake. Using microsatellite markers they revealed the genetic composition of this species within and between fairy rings based on fruiting bodies as well as ECM tips, and they provide new information about the composition of other ECM species inside, beneath and outside of the rings using ITS polymorphism analysis. Another interesting aspect of this precise work is the use of microsatellite markers on ECM root tips to identify the genotypes of both the fungus matsutake and host Pinus densiflora , which allowed the authors to provide the first direct evidence that each fungal genotype colonized multiple pine trees and vice versa. '… sexual reproduction, previously thought to play a minor role, is important for the establishment of matsutake rings.' In grass, the best-known fairy ring fungus is Marasmius oreades , commonly known as the fairy ring mushroom, which forms distinct rings or arch-like structures that result in stimulation or suppression of the surrounding plant growth and the seasonal production of fruiting bodies. The mycelium, which is found in the soil beneath the ring, interferes with plant–water relationships and produces metabolites capable of damaging grass roots. As in this species, most of the fairy-ring forming fungi are saprotrophs, but similar structures are not uncommonly produced by ectomycorrhizal fungi which sometimes but not always form these rings around a tree, as described by Last et al. (1984). Fairy rings are thought to originate from one individual, whereby the mycelium grows in a radial …