Meripilus giganteus

Meripilus giganteus, the Giant Polypore, is one of the largest soft polypores, forming massive rosette-like clusters of overlapping fan-shaped caps at the base of broad-leaved trees. The yellow-brown to snuff-brown caps and white pore surface both bruise black when handled, a feature that gives the species its other common name, the Black-staining Polypore. It is widespread in temperate hardwood forests and is commonly found on beech, oak and other broad-leaved trees, where it acts as a root and butt-rot fungus.

History

The species was transferred to the genus Meripilus by the Finnish mycologist Petter Karsten, building on the earlier descriptions of Elias Fries. Long familiar to European and North American mycologists as a conspicuous tree-base fungus, M. giganteus has been recorded at the base of hardwood trees in eastern North America, across Europe and in parts of the Himalayan region of India. Traditionally it has been regarded as edible only when young, and it has more recently attracted laboratory interest for its bioactive extracts.

Overview

Meripilus giganteus grows as a soft, fibrous polypore rather than a woody bracket: its flesh lacks the thick-walled specialised hyphae of perennial conk fungi, which is why even large fruiting bodies remain pliable. The whole cluster can reach about 75 cm across, made up of many individual fan-shaped caps that share a single fused base. The white tubes, pores and flesh stain black on bruising, and the fungus has a mild odour and slightly sour taste. As a wood-decay fungus it contributes to nutrient cycling and can weaken the root systems of host trees. Laboratory studies of its methanolic and other extracts report antibacterial activity against gram-positive bacteria, antioxidant activity, activity against the MCF-7 breast-cancer cell line and inhibition of acetylcholinesterase, the last suggesting possible relevance to Alzheimer's and related conditions.