Rhizopogon vulgaris
Description
Rhizopogon vulgaris is an ectomycorrhizal fungus used as a soil inoculant in agriculture and horticulture. It is an ectomycorrhizal truffle-forming fungus in the family Rhizopogonaceae. This species is associated with Pinaceae host trees where it exchanges mineral nutrients for photosynthates. According to Trappe et al. (2007), it is relatively common in coastal and montane conifer forests North America, particularly in the western United States. The host specificity of R. vulgaris has not been explored in great depth, but this species has been confirmed to associate with both hard and soft pine hosts (Rusca et al. 2006).
Rhizopogon is one of the most common ectomycorrhizal symbionts of the pine family (Pinaceae) in the northern hemisphere. Commonly known as ‘false truffles’, the mushrooms of this genus provide food for both wildlife and humans (Maser et al. 2009). Rhizopogon species have also been widely used in forest restoration following natural and human-made disturbances and likely play an important role in facilitating soil carbon sequestration in mycorrhizal forests.
Mushroom Identification
Outer Surface
Up to 4cm across, cream to ochraceous and often yellowish brown where exposed; rhizomorphs brownish; basal cluster of rhizomorphs, (Smith(4)), 1.5-5cm across, spherical to slightly lobate; "at first white, then yellowish tinged with reddish, finally greenish brown"; with mycelial threads, thin and branching, appressed; peridium not detachable, (Lincoff), up to 4cm across, spherical, ovate, or somewhat flattened, when large may be lobed; cream when young, "becoming yellowish tan with slight olivaceous flush (parts exposed to daylight darker brown), turning pink where bruised"; "minutely felty-fibrillose, often cracked"; "rhizomorphs inconspicuous and few on upper side", forming 1-3 rootlets in lower part, brownish, (Smith(30)), 1-4cm across, nearly spherical, ellipsoid, flattened, or irregularly lobed, frequently compound; white when young and unexposed, then yellowish white, pastel yellow, finally grayish yellow to olive brown, the white surface bruising reddish white, older or exposed surface bruising brownish red to violet brown; dry, smooth, cottony-fibrillose when young, then felty, shiny, metallic in upper part when old after prolonged exposure, when dried grayish yellow, often with patches of brighter yellow; rhizomorphs "abundant near basal attachment, coarse, free hanging, profusely branched, rarely appressed over upper surface", white bruising reddish white when young, when old white to yellowish white, often with no bruising reaction, when dried yellowish brown, appressed, conspicuous near base; peridium in cross-section 0.05-0.15cm thick, "thickest near basal attachment, flushing dull red", (Miller), pale cream when young and staining red where cut or bruised; when mature dull yellow to yellowish brown; lacking rhizomorphs on sides and top, (Trappe, M.(3))
Stem
Basal cluster of rhizomorphs (Smith(4)), rhizomorphs forming 1-3 rootlets in lower part, (Smith(30)), rhizomorphs abundant near basal attachment, (Miller)
Chemical Reactions
For dried collections, surface and spore mass quickly dark blackish-green in FeSO4, surface red in KOH but the red soon fading to rusty brown, (Smith(30)), FeSO4 on white peridium dull grey to blackish grey, negative on the older surface, negative on spore mass, KOH on white surface reddish-white, on yellow or olive areas brown, KOH negative on spore mass, (Miller)
Interior
"pallid then olive gray"; cartilaginous when fresh, sectioning readily when dried, (Smith(4)), soft; white at first, becoming greenish and finally olive-brown; with narrow maze-like chambers, (Lincoff), pallid almost to maturity; chambers empty; deliquescent when mature, (Smith(30)), soft, cake-like at first, then tough, cartilaginous, when old gelatinous; white to yellowish-white or pale yellow when young, then olive-yellow, finally olive-brown to yellowish-brown, "often mottled light to dark because of erratic maturation", young specimens with pale spore mass occasionally bruising pinkish-white, when dried grayish-yellow to yellowish-brown, (Miller), white when young, light olive by maturity.
Odor
Slight (Smith(4)), slightly acid and fruity then acrid and penetrating (Lincoff), faint, like Scleroderma, or in some mature specimens strong and offensive, (Smith(30)), similar to the commercial mushroom when fresh, when old strongly of road tar, (Miller)
Taste
Initially sweet (Lincoff), mild (Trappe, M.(3))
Microscopic
Spores 5.5-8 x 2-2.6 microns, many subfusoid; "peridium of appressed hyphae, no pockets of vesiculose cells seen, in KOH finally fulvous near the surface" and nearly colorless toward the spore mass, with copious pigment in peridium as revived in KOH, (Smith(4)), spores 5-8 x 2-3 microns, elliptic, smooth, whitish, (Lincoff), spores 5.5-8 x 2-2.6 microns, narrowly subfusoid to elliptic varying to oblong, smooth, in Melzer''s reagent yellowish singly and in groups, in KOH colorless singly and yellowish in groups, with inconspicuous basal scar; basidia 4-spored and 8-spored, 14-17 x 4-5 microns, "subcylindric, readily collapsing"; paraphyses 10-18 x 4-10 microns, subspherical to clavate or vesiculose and thin-walled; cystidia none; "subhymenium poorly developed and individual cells indistinct in revived material"; tramal plates "with gelatinous highly refractive hyphae more or less interwoven"; peridium of "appressed-interwoven hyphae at first red in KOH but soon fading out to fulvous and with orange-brown pigment globules in upper region (in Melzer''s sol.), no pockets of vesiculose cells noted", the part next to the gleba finally nearly colorless; all tissues inamyloid; clamp connections none, (Smith(30)), spores 7.5-9.5(10.5) x 2.5-3.0 microns, subcylindric, oblong to narrowly subfusoid, often slightly curved in side view, in Melzer''s reagent pale yellow singly, dull olive yellow in mass, mostly with 2-3 lipid droplets, in KOH pale yellow singly, dull yellowish gray in mass, basal scar present but not prominent; basidia borne in a distinct hymenium, 12-18 x 4-5 microns, subcylindric to narrowly clavate, "thin-walled and soon collapsing, mostly 8-spored", brachybasidioles 10-20 x 6-10 microns, subspherical, clavate, or obovate, thin-walled when young, thick-walled, mucilaginous when old, not readily disarticulated in crush mounts; subhymenium poorly developed, composed of branching, colorless, thin-walled or thick-walled, cylindric or cubic hyphae; trama of hyphae that are 4-7 microns wide, colorless, highly refractive in KOH, cylindric to slightly swollen, thin-walled when young, mucilaginous when old, oleiferous hyphae present in mediostratum, 6-12 microns wide, hyaline refractive to deep yellow in KOH and in Melzer''s reagent, "cylindric or irregularly swollen and contorted"; peridium 300-360 microns thick, peridial subcutis a layer of hyphae that are 6-14 microns wide, cylindric, appressed, interwoven, and thin-walled, oleiferous hyphae abundant, 8-20 microns wide, dark yellowish brown in KOH and in Melzer''s reagent, cylindric or irregularly swollen and contorted, occasionally branching, slightly gelatinized when old, "lightly encrusted with amorphous pigment that is orange brown to reddish brown in KOH, orange brown in Melzer''s reagent, readily liquefying into large, compound orange brown pigment globules", peridial epicutis a turf of spherical to ovoid, thin-walled, inflated cells; clamp connections absent, (Miller)
Synonyms
Hysteromyces vulgaris Vittad., 1844
Rhizopogon rubescens var. vittadinii Tul. & C. Tul., 1851
Rhizopogon vittadinii (Tul.) Zeller, 1939
Photo sources:
Photo 1 - Author: jacilluch (CC BY-SA 2.0)
