Truffles & Tuckahoes

truffle fungus
D. Andrew White 12/16/2010

Truffles are fungi that form their fruiting bodies underground. The spores remain in the ‘toadstool’ until disseminated by animals. Several fungi of the genus Tuber are sought as food items in the forested regions of southern Europe. These Tuber species are ascomycetes or 'sac-fungi'. Dogs can be trained to detect truffles by smell. However, the detection of the truffle odour comes quite naturally to pigs. Traditionally pigs were, and still sometimes are, used in truffle hunting (Del Conte & Læssøe 2008).

(1) Tartufo d'Alba: White truffle (Tuber magnatum) is one example of a highly prized underground mushroom. It is smooth, soft, marbled, and it tastes both spicy and mushroomy. Only a tiny amount is sufficient to flavour food. It grows mostly in calcareous soil, mostly in the Piedmont region of Italy.
Perigord truffle: Perigord truffle (Tuber melanosporum) has a dark scaly exterior and marbled interior. It is found throughout the southern Mediterranean area, mostly in reddish pedalfer soils. It grows mostly near oak roots.

(2) Pine truffles: Pine truffles are ascomycetes that are typically found in mycorrhizal association with conifers. The Oregon truffle (Tuber gibbosum) is delicious like its Old World counterpart. It grows mostly under Douglas fir. The pine truffle (Geopora cooperi), of the American West, grows under both conifers and willows. The Geospora is an example of a truffle that is derived from an aboveground cup-fungus. Basically, it has a cup-like apothecium, but this structure is crumpled-up into a tight ball. The same is true for the species in the genus Tuber - but less obviously so. Pine truffles are eaten by squirrels (Loeb et al 2000). They are rather flavourful fungi, on the whole.

(3) Deer truffles: Various truffle-like fungi are fairly common in eastern North America. The Elaphomyces are ascomycetes with truffle-like sporocarps. The genera Gymnomyces and Rhizopogon are basidiomycetes that also produce truffle-like bodies. Some of these deer truffles are edible, others are tough in texture, and yet others engulf the sand in which they grow. Deer truffles are not only eaten by deer, they are also eaten by squirrels and voles (Loeb et al 2000, Trappe et al 2007). These animals find the fruiting bodies by their distinctive odour. Deer truffles are widely considered to have an 'insipid' flavour.

(4) Pseudo-truffles: Basidiomycete false-truffles do occur. The conifer forest false truffles (Truncocolumella spp.) are a club fungi. In fact, they are genetically close to the boletes - though having a puffball-like anatomy. Many false truffles appear to be derived from above ground toadstools. They are structured very much like toadstools that are ‘aborted’ in their development. The stipe, the columella and the gleba all are all arranged as in a 'normal' toadstool. The bolete false-truffles (Gastroboletus spp.) produce bolete-like mushrooms which do not usually break through the leaf litter. There is a false-truffle (Radiigera fuscogleba) that is basically a sort of aborted earthstar.

(5) Mouse Truffles: Glomeromycetes in the genus Glomus can produce small truffle-like bodies. Similarly, zygomycetes in the genus Endogone produce truffle-like sporocarps. These fungi form endomycorrhizal associations with many species of plants. Their spores are spread by rodents such as mice and voles. Their sporocarps are too small, and sandy, for human consumption (Trappe et al 2007).

(6) Tuckahoes: Some false-truffles form an underground sclerotium. A sclerotium is a means by which a fungus survives drought or winter. It is not a fruiting body, the actual toadstool is aboveground. The commonest tuckahoe (Wolfiporia cocos) looks very much like a truffle. It can be as large as a coconut. These tuckahoes were eaten by the Algonquins and other Amerindian peoples. Another tuckahoe species (Polyporus tuberaster) is similar, but its aboveground toadstool is more often found. Its sclerotium tends to be sandy and is semi-edible at best. The Australian version of the tuckahoe (Laccocephalum mylittae), once called Mylitta australis, is very similar. This fungus was once used as a food source by the Aboriginal Australians. Hypogeous sclerotia are fairly common in dry environments, such as the American prairies and the Australian outback.

truffle fungus

References

Del Conte, Anna and Læssøe, Thomas. 2008. The Edible Mushroom Book. DK Publishing. New York.

Loeb, S.C., Tainter, F.H. and Cazares, E. 2000. Habitat associations of hypogeous fungi in the southern appalachians: Implications for the endangered northern flying squirrel (Glaucomys sabrinus coloratus). America Midland Naturalist. 144(2):286-296.

Thomas, William S. 2003. Field Guide to Mushrooms. Sterling Publishing Co., Inc. New York.

Trappe, M., Evans, F. and Trappe, J. 2007. Field Guide to North American Truffles. Ten Speed Press. Berkeley CA

Bioluminescent Fungi

jack-o-lantern glowing toadstool honey mushroom - glowing mycelia

There is a catch-all rural American term for weird glowing spots in in the wilderness: “foxfire”. Foxfire is sometimes just will-o’-the-wisp, or natural flames of burning methane (swamp gas). Other times the spooky lights are caused by bioluminescent organisms. Many organisms can produce visible light. Firefly beetles, many algae, and a host of fungi can glow in the dark.

Masses of the honey mushroom’s mycelium can glow eerily on dark nights. Mostly this mycelial mat is hidden under bark, but on occasion it is noticeable. Jack-o’-lantern toadstools also can glow in the dark. In this case, a whole group of fungal fruiting bodies may be seen glowing feebly on dark nights. In both cases, the chemical reaction radiates a bluish-green light. The glow is ‘cool’, except perhaps at a micro-molecular level. Of course, immobile glowing fungi cannot explain all will-o’-the-wisp sightings. Some spook lights move, and hence must have another explanation.

The adaptive function of fungal bioluminescence is not fully known. It is most common in wood rotting fungi. In many cases bioluminescence seems to be a side effect of oxygen respiration. The light producing enzymatic reactions are also involved in the creation of metabolic water. In some species, the glowing tissues may attract insects, which help to disperse the spores. In actual fact, even though the biochemical process is fairly well understood, its full biological role is still an enigma.

Endophytic Fungi

conidia asci conidia

Endophytic fungi are a group of fungi which live asymptomatically inside plant tissues. These fungi were first noticed in the 1940s, but only at the turn of the 21st century was the ubiquity of these fungi fully recognised. They live like fungi imperfecti, much of the time, producing mostly conidial spores or simply cloning themselves. They are between benign parasites and true symbionts in their behaviour. Although, many endophytic fungi become rotting agents upon the death of their host plant. Sometimes they may produce toxins in response to pests which feed on their host’s tissues. These toxins benefit the host plant. For example, there are endophytes which make grass poisonous to grazing animals. Other endophytes, in oak leaves, ward off gall midges. In the sense that these ‘endophytes’ can protect their host, they are symbionts. Endophytes are low-key examples of symbiosis (Heinrich 1997, Schardl et al 1997, Meijer & Leuchtmann 1999).

Endophytes belong to several fungal taxonomic groups, but most are ascomycetes. Many of the needle cast fungi (e.g. Phomopsis spp. & Lophoderma spp.), have endophytic relatives. Even some of the leaf spot diseases (e.g. Rhytisma spp.) have endophytic relations. Most of the endophytes which infect pines are members of the Rhytismataceae family. Since there are rhytismataceous parasites, mycologist have wondered if endophytes are not just the old familiar parasites in dormancy mode. Genetic studies show that the rhytismataceous endophytes are not the same as their pathogenic cousins. They are members of the same genera, but they are not identical species (Ganley et al 2004). Endophyticity seems to be a niche different from parasitism. Possibly this mode of life developed from true parasitism.

An Example of an Endophytic Fungus

“A certain man sowed good seed in his field, but in the night, whilst men slept, his enemy came and sowed tares among the wheat, and went his way.”
Matthew 13:24-25.

‘Tares’ is an old name for the darnel ryegrass (Lolium temulentum) of Eurasia and North Africa. It is widely considered a weed, even being despised as a source of fodder. This little divertimento into agronomy does relate to mycology somehow – bear with me.

Darnel ryegrass, or tares, was a scourge of cereal farmers and haymakers alike. In the olden days wheat, and other cereals, were often contaminated by the seeds of wild grasses. Darnel contaminants often made wheat flour both poisonous and distasteful. Cattle sometimes became ill from too much darnel in their hay. In sheep it could cause staggers disease. Tares seldom infest hay and cereal crops nowadays. Seed-corn is cleaner now than it was in yesteryear. This is why the word ‘tares’ is not so familiar to twenty-first century folks.

Darnel gets its toxicity from temuline, an alkaloid. This poison is produced by an endophytic fungus (teleomorph: Gloeotinia temulenta). In darnel ryegrass, the fungus occurs mostly in its asexual form (anamorph: Endoconidium temulentum). However, the fungus does produce sexual ascomata when it grows on other species of ryegrass. In these other hosts it causes the blind seed disease, or seed abortion. In effect, outside of its native host this endophytic fungus becomes a pathogenic fungus.

References

Coder, Kim D. 2004. Foxfire - secret lights in the chipper box. I.S.A. Arborist News. 13 (5): 5-8.

Corliss, William R. 1983. Hand Book of Unusual Natural Phenomena. Anchor Press. Garden City New York.

Ganley, Rebecca J., Brunsfeld, Steven J. and Newcombe, George. 2004. A community of unknown, endophytic fungi in western white pine. PNAS, July 6, 101 ( 27):| 10107-10112

Heinrich, Bernd. 1997. The Trees of My forest. Cliff Street Books. New York.

Holliday, Paul. 1989. A Dictionary of Plant Pathology. Cambridge University Press. Cambridge.

Lee, Robert Edward. 1999. Phycology. 3rd Edition. Cambridge University Press. Cambridge.

McLoughlin, Stephan and Vajda, Vivi. 2005. Ancient wollemi pines resurgent. American Scientist. 93 (6): 540-547.

Meijer, G. and Leuchtmann, A. 1999. Multistrain infections of the grass Brachypodium sylvaticum by its fungal endophyte Epichloë sylvatica. New Phytologist, 141: 355-368.

Schardl, C. L., Leuchtmann, A., Chung, K.-R., Penny, D., and Siegel, M. R. 1997. Coevolution by common descent of fungal symbionts (Epichloë spp.) and grass hosts. Molecular Biology and Evolution. 14: 133-143.

Schwarze, F.W.M.R., Engels, J. and Mattheck, C. 2004. Fungal Strategies of Wood Decay in Trees. Springer. Berlin.

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