Suillus spraguei

What You Should Know

Suillus spraguei is an ectomycorrhizal mushroom-forming fungus in the family Boletaceae. Fruiting bodies of this fungus have bright reddish caps covered with dry red hairs, enlarged radial pores, whitish cottony partial veil remnants on the stipe, and stipe covered by reddish hairs similar to the cap.

Widely distributed across eastern North America, and also occurs in eastern Asia (Japan, China).

Other names: Painted Slipperycap, The Painted Suillus, The Red and Yellow Suillus.

Suillus spraguei Mushroom Identification

1. Ecology

   Mycorrhizal with eastern white pine; growing alone or gregariously; late summer and fall; northeastern North America, extending as far west as Minnesota and as far south as Kentucky.

2. Cap

   3-12 cm; convex with an inrolled margin when young, but soon broadly convex to flat; covered with large pinkish to brick-rose scruffies; whitish partial veil tissue often hanging from the margin; dry; fading with age.

3. Pore Surface

   Covered with a whitish partial veil when young; yellow, darker with age; sometimes slightly running down the stem; sometimes bruising reddish or brownish; pores small to large, 0.5-5 mm across, vaguely radially arranged; tubes 4-8 mm deep.

4. Stem

   4-12 cm long; 1-2.5 cm thick; equal or sometimes wider in the base; without glandular dots, but shaggy with scruffies below the whitish to grayish ring; not bruising; frequently with a whitish to grayish ring.

5. Flesh: Yellow throughout, sometimes staining slightly reddish.

6. Spore Print: Brown.

Suillus spraguei Edibility

It is mainly not highly regarded, but some sources considered it to be “choice” edible. Too bad that it turns black when cooked and does not preserve beautiful colors. Even when cut or damaged, the flesh turns from yellow to black.

Drying concentrates flavor and avoids any issues with a slimy cuticle.

Suillus spraguei Ecology, Habitat and Distribution

In nature, Suillus spraguei forms ectomycorrhizal relationships with five-needled pine species. This is a mutually beneficial relationship where the hyphae of the fungus grow around the roots of the trees, enabling the fungus to receive moisture, protection and nutritive byproducts of the tree, and affording the tree greater access to soil nutrients. S. spraguei produces tuberculate ectomycorrhizae (covered with wart-like projections) that are described as aggregates of ectomycorrhizal roots encased in a fungal rind, and rhizomorphs that are tubular fungal cords with a hard outer sheath.

The fungus has ecological host specificity, and in natural soils can only associate with white pine, a grouping of trees classified in subgenus Strobus of the genus Pinus. Under controlled pure culture conditions in the laboratory, S. spraguei has also been shown to form associations with red pine, pitch pine, and loblolly pine. Asian populations have been associated with Korean pine, Chinese white pine, Siberian dwarf pine and Japanese white pine.

In North America, fruit bodies appear earlier than most other boletes, as early as June (bolete fruit bodies generally begin to appear in July–September), but they may be found as late as October. Mushrooms can be parasitized by the fungus Hypomyces completus. In the asexual stage of H. completus, it appears initially as patches of whitish mold on the surface of the cap or stem that rapidly spread to cover the entire mushroom surface and produce conidia (asexual spores). In the sexual stage, the mold changes color, progressing from yellow-brown to brown, greenish-brown and eventually black as it makes perithecia, asci-containing sexual structures that produce ascospores. The perithecia are pimply and give the surface a roughened texture.

A Japanese field study found that S. spraguei was the dominant fungus in a 21-year-old stand of Korean pine, both in terms of ectomycorrhizae (measured as percentage of biomass present in soil samples) and by fruit body production (comprising over 90% of dry weight of total fruit bodies collected of all species). The production of S. spraguei fruit bodies averaged about one per square meter, without much variance during the four-year study period.

The mushrooms appeared mostly from August to November, tended to grow in clumps, and the spatial distribution of clumps was random—the location of the clumps was not correlatable with appearances in previous years. The density of mushrooms along a forest road was higher than average, suggesting a preference for disturbed habitat. The results also suggested that S. spraguei prefers to produce fruit bodies in areas with low litter accumulation, a finding corroborated in a later publication. This study also determined that the fungus propagates mainly by vegetative growth (extension of underground mycelia), rather than by colonization of spores.

Suillus spraguei has a disjunct distribution and is known from several localities in Asia, including China, Japan, Korea, and Taiwan. In North America, its range extends from eastern Canada (Nova Scotia) south to the Carolinas, and west to Minnesota. It has also been collected in Mexico (Coahuila and Durango). Furthermore, the species has been introduced to Europe (Germany, Lower Saxony; Netherlands).

Suillus spraguei Taxonomy and Etymology

The first specimen was originally collected in New England in 1856 by Charles James Sprague, and a formal scientific description was published in 1872 when Miles Joseph Berkeley and Moses Ashley Curtis called it Boletus spraguei. In a publication that appeared the following year, American mycologist Charles Horton Peck named the species Boletus pictus. Berkeley and Curtis had also described what they believed to be a new species - Boletus murraii - although this was later considered by Rolf Singer to be merely a younger version of their Boletus spraguei.

Peck's description appeared in print in 1873, but the date stamp on the original publication revealed that he had sent his documents to the printer before the appearance of the 1872 Berkeley and Curtis publication, thus establishing nomenclatural priority under the rules of fungal naming.

In 1945 Singer reported that the name Boletus pictus was illegitimate because it was a homonym, already being used for a polypore mushroom described by Carl Friedrich Schultz in 1806.

A 1996 molecular analysis of 38 Suillus species used the sequences of their internal transcribed spacers to infer phylogenetic relationships and clarify the taxonomy of the genus. The results indicate that S. spraguei is most closely related to S. decipiens. The species S. granulatus and S. placidus lie on a branch sister to that containing S. spraguei. These results were corroborated and extended in later publications that assessed the relationships between Asian and eastern North American isolates of various Suillus, including S. spraguei.

The analysis supported the hypothesis that Chinese and U.S. S. spraguei and S. decipiens were each other's closest relatives, and the clade that contained them could be divided into four distinct subgroups: S. decipiens, U.S. S. spraguei, China (Yunnan) S. spraguei, and China (Jilin) S. spraguei.

The specific epithet spraguei is an homage to the collector Sprague, while pictus means "painted" or "colored". Suillus spraguei is commonly known as the "painted slipperycap", the "painted suillus", or the "red and yellow suillus". It is also called the "eastern painted Suillus" to contrast with the "western painted Suillus" (Suillus lakei).

Sources:

Photo 1 - Author: Jimmie Veitch (jimmiev) (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 2 - Author: William Tanneberger (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 3 - Author: Paul Derbyshire (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 4 - Author: walt sturgeon (Mycowalt) (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 5 - Author: Paul Derbyshire (Creative Commons Attribution-Share Alike 3.0 Unported)