Norwegian fungus of the month, October 1999

Marasmius oreades(Bolt.: Fr.) Fr.

(Tricholomataceae, Agaricales, Basidiomycota)


Marasmius oreades is one of the most common fairy ring mushrooms in Southern Norway. It occurs in natural and semi-natural grasslands as well as in lawns. The fungus can sometimes be destructive to lawns and pastures. The rings or arcs in the turf produced by the fungus can be recognised by the stimulation or suppression of grass growth. The basidiocarps usually develop after heavy precipitation. They endure dessication and can be resurrected by repeated rainfalls. The mycelium is found in the soil to the outside and beneath the ring. It is thick and hydrophobic. It has been suggested that the mycelium may interfere with the penetration of water and that the grasses suffer from drought. The fungus can parasitise grass roots.


DESCRIPTION and DISTRIBUTION MAP FOR NORWAY

Fairy rings are distinct ring or arch structures generally recognized by the stimulation or suppression of surrounding plant growth and the production of aerial basidiocarps - mushrooms. They are common phenomena in pastures and are present in numerous habitats, especially in coastal ecosystems. Furthermore, fairy rings are considered a turfgrass disease that can be very destructive to lawns, golf courses, parks and athletic fields. Their mycelia interferes with plant-water relationships and produces hydrogen cyanide and sesquiterpene metabolites capable of damaging the grass roots (Traquair and McKeen 1986, Ayer and Craw 1989).



The establishment of Marasmius oreades is poorly understood. Couch (1973) suggested that fragments of dikaryotic mycelia are probably the main sources of inoculum. On the other hand, Mallett and Harrison (1988) demonstrated that most fairy rings were likely started by spores because either their mating types differed or they shared the same mating type genotype, but were genetically distinct, based upon vegetative interactions between dikaryotic isolates. The fairy rings can be old, 100-150 years, possibly 500 years (Burnett and Evans 1966). The mating system is heterothallic and unifactorial, the locus controlling sexuality being multiallelic (Mallett and Harrison 1988). However, the fungus has not been studied with contemporary molecular genetic techniques that would better define its genetics and population structure.


In the sand dune ecosystems on the Lista peninsula (Farsund community, Vest-Agder county, SW Norway) Marasmius oreades is a characteristic fungus in the dry dune pastures behind the outer dune ridges (Høiland 1977). The dominating grasses in these pastures are Festuca rubra, Poa pratensis ssp. subcaerulea, and Corynephorus canescens (Høiland 1978). In more unestablished pastures, Marram Grass Ammophila arenaria is frequent. Numerous lowland or coastal species of herbs occur in these dune pastures, some frequent on the more pioneer sites, other dominating on the more established areas. Mosses and lichens are also common. The different species of grasses, herbs, mosses, and lichens usually occur in mosaic patterns. In the dune ecosystem, Marasmius oreades seems to have a restricted occurrence. It is confined to the dry dune pastures, avoiding the outer dunes, and is totally lacking in the wetter dune slacks and Salix repens dominated vegetation types (Høiland and Elven 1980). Høiland (1993) carried out a pilot study investigating the fairy rings of Marasmius oreades along a transect from pioneer to established vegetation in dune pastures on Lista. There was a significant positive correlation between the diameter of the ring and the distance from the outermost dune ridge. A corresponding correlation was found between the diameter and the number of plant species recorded in 15 x 15 cm squares lain upon the rings.


A more comprehensive study of the fairy rings of Marasmius oreades on Lista was started in 1996. The idea was to establish a couple of areas of 500-1000 m2 and measure all fairy rings that would appear inside these areas during a series of three years. The occurrence, size and form of the fairy rings were compared with vegetation analyses, and the yearly production of fruit bodies in the various rings with climatological data from the nearest weather station, Lista Lighthouse.


Two areas, A and B, of approx. 560 and 1750 m2 respectively were established on the little peninsula of Einarsneset (UTMED50 LK 69 38) SE on Lista. Area A is a sand plain sheltered from the prevailing western winds by rocks (in west and north) and otherwise delimited by dune ridges and blow outs with naked sand. Area B is a part of a moving sand dune system with building Ammophila dunes in west. Eastward there is a succession from fixed Ammophila dunes, dune pastures, to dune heaths. The delimitation of area B was set arbitrarily to cover a representative part of the vegetation succession where Marasmius oreades is found. One of the main goals is to elucidate the genetic structure of the different rings. Are they clonal (e.g. formed by ramifications of old rings) or have they originated from spores. In other words, are the rings ramets or genets. Various DNA fingerprinting methods may prove useful to study the genetic structure of the fairy ring populations on Lista.


References:

Ayer, W.A. and Craw, P.A. 1989. Metabolites of the fairy ring fungus Marasmius oreades: Norsesquiterpenes, further sesquiterpenes and agrocybin. Can. J. Chem. 67: 1371-1380.

Burnett, J.H. and Evans, E.J. 1966. Genetic homogeneity and the stability of the mating-type factors of the "fairy rings" of Marasmius oreades. Nature (Lond.) 210: 1368-1369.

Couch, H.B. 1973. Diseases in turfgrasses, 2nd ed, RE Krieger Pub Co, Huntington, NY.

Høiland, K. 1977. Storsopper i etablert sanddyne-vegetasjon på Lista, Vest-Agder. 1. Progressive systemer. Blyttia 35: 139-155.

Høiland, K. 1978. Sand-dune vegetation of Lista, SW Norway. Norw. J. Bot. 24: 249-254.

Høiland, K. 1993. Studier av hekseringer av nelliksopp (Marasmius oreades) i dyne-grashei på Lista (Vest-Agder). Polarflokken 17: 371-383.

Høiland, K. and Elven, R. 1980. Classification of fungal synedria on coastal sand dunes at Lista, South Norway, by divisive information analysis. Norw. J. Bot. 27: 23-29.

Mallett, K.I. and Harrison L.M. 1988. The mating system of the fairy ring fungus Marasmius oreades and the genetic relationship of fairy rings. Can. J. Bot. 66: 1111-1116.

Traquair, J.A. and McKeen, W.E. 1986. Fine structures of root tip cells of winter wheat exposed to cultural filtrates of Coprinus psychromorbidus and Marasmius oreades. Can. J. Plant Pathol. 8: 59-64.