Purple-veiled Slippery Jack

The cap is chestnut, rusty, olive brown, or dark brown in color with a diameter of 4–10 centimetres (1+1⁄2–4 in), rarely up to 20 cm. The cap has a distinctive conical shape, later flattening out. It is slimy to the touch, bare, smooth, and glossy even when dry, and the cuticle is easily peeled off. The tiny, circular pores of the tubes are initially yellow but turn olive to dark yellow with maturity. Like the skin of the cap, they can be readily peeled away from the flesh. Tubes comprising the hymenophore on the underside of the cap are 3–7 mm (1⁄8–1⁄4 in) deep, with an attachment to the stipe ranging from adnate to somewhat decurrent. The pores are tiny, numbering 3 per mm in young specimens and 1–2 per mm in maturity. The stipe is 5–10 cm (2–4 in) tall and 2–3 cm (3⁄4–1+1⁄4 in) wide. It is pale yellow and more or less cylindrical but may bear a swollen base. A membranous partial veil initially links the stipe with the edge of the cap. When it ruptures, it forms a membranous, hanging ring. The top side of the ring is whitish, while the underside is characteristically dark brown to violet. This species is one of the few members of the genus Suillus that have such a ring. Above the ring, the stipe features glandular dots—minute clumps of pigmented cells. Below the ring, the stipe is dingy white, sometimes streaked with brownish slime. …

Suillus luteus can be found all over the Northern Hemisphere. Native to Eurasia, it is widespread across the British Isles. To the east it has been recorded from Pakistan, where it was found along canals in Dashkin in the district of Astore, and as far east as South Korea. It has also been widely introduced elsewhere by way of pine plantations around the globe. It is very commonly found in Monterey pine (Pinus radiata) plantations, despite the tree being native to California and hence not in the fungus' native range. In North America it is found in the northeastern, northwestern, and southwestern United States. According to Ernst Both, it was Charles Horton Peck who first suggested in 1887 that the fungus was introduced to the state of New York on Pinus sylvestris. DNA studies show that the North American populations differ little genetically from European populations, supporting the idea that the fungus arrived to North America relatively recently as a result of human activity. Suillus luteus is found in coastal and mountainous pine forests and exhibits a tolerance of the northern latitudes. Southern Hemisphere locales where the slippery jack grow with plantation pines include South America, Africa, Australia, and New Zealand. In southwestern Australia, the bolete is limited to areas of greater than 1000 mm (40 in) annual rainfall. …

Suillus luteus is a pioneer species that typically establishes itself in the early stages of forest succession. The fungus forms mycorrhizal associations with various species of pine, including Scots pine (P. sylvestris), black pine (P. nigra), and Macedonian pine (P. peuce) in Europe, and red pine (P. resinosa) and white pine (P. strobus) in North America. An in vitro experiment demonstrated that the species could form an ectomycorrhizal association with Aleppo pine (P. halepensis), a key species used in reforestation in the Mediterranean. A study of the ectomycorrhizal fungi associated with a lodgepole pine (P. contorta) invasion front near Coyhaique, Chile, showed that many invasive trees were supported by S. luteus as the sole mycorrhizal partner. The ectomycorrhizae formed between the fungus and host plant can be influenced by soil microorganisms present in the mycorrhizosphere. For example, soil bacteria from the genera Paenibacillus and Burkholderia alter the branching structure of the root, whereas Bacillus species increase root growth and mycorrhizal colonization. The fungus does not require a specific soil but seems to prefer acidic and nutrient-deficient soil. Suillus luteus produces hydroxamic acid-based siderophores, which are compounds that can chelate iron and extract it from the soil in nutrient-poor conditions. …

Suillus luteus is an edible mushroom, but the slime/pileipellis must be removed. Although some authors regard it as one of low quality, and generally inferior to co-occurring species such as Boletus pinophilus, the species is considered a delicacy in Slavic cultures (known as maslyata in Russian or maslyuky in Ukrainian or maślaki in Polish, deriving from words meaning "buttery"). It was highly regarded in Calabria, even more than Boletus edulis, until the 1940s when increased interest in the latter species eclipsed the former. Mushrooms conforming to Suillus luteus are exported from Chile to Italy, and, since the 1970s, the United States. As of 2002, harvesters in Chile were paid on average US$0.5 per kilogram of fruit bodies. In Burundi, Suillus luteus mushrooms are sold to Europeans as cepes in Bujumbura but not generally eaten by the Barundi. Based on samples collected from Chile, the boletes contain (as a percentage of dry weight) 20% protein, 57% carbohydrates, 6% fat, and 6% ash. …