King Bolete

Description:

Boletus edulis, commonly known as penny bun, porcino or cep, is a basidiomycete fungus, and the type species of the genus Boletus. Widely distributed in the Northern Hemisphere across Europe, Asia, and North America, it does not occur naturally in the Southern Hemisphere, although it has been introduced to southern Africa, Australia and New Zealand. Several closely related European mushrooms formerly thought to be varieties or forms of B. edulis have been shown using molecular phylogenetic analysis to be distinct species, and others previously classed as separate species are conspecific with this species. The western North American species commonly known as the California king bolete (Boletus edulis var. grandedulis) is a large, darker-coloured variant that was first formally identified in 2007. The fungus grows in deciduous and coniferous forests and tree plantations, forming symbiotic ectomycorrhizal associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue. The fungus produces spore-bearing fruit bodies above ground in summer and autumn. The fruit body has a large brown cap which on occasion can reach 35 cm (14 in) in diameter and 3 kg (6.6 lb) in weight. Like other boletes, it has tubes extending downward from the underside of the cap, rather than gills; spores escape at maturity through the tube openings, or pores. The pore surface of the B. edulis fruit body is whitish when young, but ages to a greenish-yellow. The stout stipe, or stem, is white or yellowish in colour, up to 25 cm (10 in) tall and 10 cm (3.9 in) thick, and partially covered with a raised network pattern, or reticulations. Prized as an ingredient in various foods, B. edulis is an edible mushroom held in high regard in many cuisines, and is commonly prepared and eaten in soups, pasta, or risotto. The mushroom is low in fat and digestible carbohydrates, and high in protein, vitamins, minerals and dietary fibre. Although it is sold commercially, it has not been successfully grown in cultivation. Available fresh in autumn in Central, Southern and Northern Europe, it is most often dried, packaged and distributed worldwide. Keeping its flavour after drying, it is then reconstituted and used in cooking. Boletus edulis is one of the few fungi that are sold pickled. The fungus also produces a variety of organic compounds with a diverse spectrum of biological activity, including the steroid derivative ergosterol, a sugar binding protein, antiviral compounds, antioxidants, and phytochelatins, which give the organism resistance to toxic heavy metals.

Habitat:

The fruit bodies of Boletus edulis can grow singly or in small clusters of two or three specimens. The mushroom's habitat consists of areas dominated by pine (Pinus spp.), spruce (Picea spp.), hemlock (Tsuga spp.) and fir (Abies spp.) trees, although other hosts include chestnut, chinquapin, beech, Keteleeria spp., Lithocarpus spp., and oak. In California, porcini have been collected in a variety of forests, such as coastal forests, dry interior oak forests and savannas and interior high-elevation montane mixed forests,[47] to an altitude of 3,500 m (11,500 ft).[48] In northwestern Spain, they are common in scrublands dominated by the rock rose species Cistus ladanifer and Halimium lasianthum.[49] Boletus edulis has a cosmopolitan distribution, concentrated in cool-temperate to subtropical regions.[47] It is common in Europe—from northern Scandinavia, south to the extremities of Greece and Italy—and North America, where its southern range extends as far south as Mexico.[33] It is well known from the Borgotaro area of Parma, Italy, and has PGI status there. The European distribution extends north to Scandinavia and south to southern Italy and Morocco.[47] In China, the mushroom can be found from the northeastern Heilongjiang Province to the Yunnan-Guizhou Plateau and Tibet.[33] It has been recorded growing under Pinus and Tsuga in Sagarmatha National Park in Nepal,[50] as well as in the Indian forests of Arunachal Pradesh.[51

Notes:

Although Italian folklore holds that porcini sprout up at the time of the new moon,[17] a number of research studies have tried to investigate more scientifically the factors that influence the production of fruit bodies. Although fruit bodies may appear any time from summer to autumn, their growth is known to be triggered by rainfall during warm periods of weather followed by frequent autumn rain with a drop in soil temperature.[47] Above average rainfall may result in the rapid appearance of large numbers of boletes, in what is known in some circles as a "bolete year".[56] A 2004 field study indicated that fruit body production is enhanced by an open and sunny wood habitat,[57] corroborating an earlier observation made in a Zimbabwean study;[55] removal of the litter layer on the forest floor appeared to have a negative effect on fruit body production, but previous studies reported contradictory results.[58][59] A Lithuanian study conducted in 2001 concluded that the maximal daily growth rate of the cap (about 21 mm or 0.8 in) occurred when the relative air humidity was the greatest, and the fruit bodies ceased growing when the air humidity dropped below 40%. Factors most likely to inhibit the appearance of fruit bodies included prolonged drought, inadequate air and soil humidity, sudden decreases of night air temperatures, and the appearance of the first frost.[60] Plots facing north tend to produce more mushrooms compared to equivalent plots facing south.