Butyriboletus fechtneri

Description

Butyriboletus fechtneri is a rare basidiomycete fungus in the family Boletaceae. It is large to medium-sized, pale to light brown, boletoid, without veil and ring. The stem is solid, with a surface usually covered with granules or network. The flesh is variously colored, changing or not when exposed to air. It is native to Europe, where it forms ectomycorrhizal associations with various broad-leaved trees of the family Fagaceae, particularly oak (Quercus), beech (Fagus) and chestnut (Castanea).

Even though it is an excellent edible mushroom, its collection is prohibited by law in most EU countries. It is classified as an endangered species (EN) in the Red List of Mushrooms of the Czech Republic. In Switzerland (VU = vulnerable), RL2 Germany (endangered). Fully protected according to the Federal Species Protection Act Germany.

Common names: Pale Bolete, Bleke boleet (Netherlands), German: Silberröhrling, Sommerröhrling, Hřib Fechtnerův (Czech Republic).

Mushroom Identification

1. Cap

   The cap is 5-15 (20) cm in diameter, fleshy, initially hemispherical, later convex, convex-spreading, pillow-like-spreading. The cap surface is initially silky-fibrous, later smooth, shiny, slightly wrinkled, sticky in wet weather, silver-white, grayish-brownish, light brown.

2. Pores

   The hymenophore is tubular. The pores are small, rounded, at first bright yellow, later olive yellow, turning blue in places of contact.

3. Stem

   The stem is 4-15 cm high, 2-6 cm in diameter, at first tuberous, then elongated, thickened at the base, solid, yellowish at the top and at the bottom, yellowish-reddish in the middle part, with a thin indistinct yellow mesh in the upper part.

4. Flesh

   The flesh is dense, fleshy, yellow, reddish at the base of the stem, bluish in cut, with a pleasant taste and smell. The flesh is very often invaded by larvae.

5. Spores

   9–15 × 3.5–5.5 μm, ratio 2–3.4. Pileipellis (the cap cuticle) trichodermium of interwoven septate hyphae. Cells of the hyphae cylindrical, finely incrusted.

6. Spore Print

   Olive-yellow.

7. Chemical Reactions

   Hyphae of the flesh in the stipe base inamyloid with Melzer’s solution.

8. Habitat

   Grows from June to September, in deciduous forests, with oaks and beeches, singly and in small groups. It is more often seen in certain mainland European countries, particularly in central and southern Europe. It is a heat-loving species of lower altitudes. It occurs on limestone and other basic soils in areas of thermophilic flora.

Look-Alikes

1. Rubroboletus satanas

   The cap is chalky white with red pores and a bulbous red stem.

2. Caloboletus calopus

   It has a light cap and yellow pores. Its stem is yellow towards the tip and red base.

3. Boletus radicans

   Inedible, bitter, no red stem, grows only in forests deciduous

4. Boletus spinarii

   Inedible, without reddish tones.

5. Butyriboletus regius

   Has a pink cap with a different color of tube and stem.

6. Caloboletus radicans

   Has bitter flesh and smells of urea when dried.

7. Hemileccinum impolitum

   Pale unchanging flesh, no mesh.

8. Butyriboletus appendiculatus

   Has a deep brown cap.

9. Butyriboletus fuscoroseus

   Noticeable pink tones in the color of the cap, which are missing in B. fechtneri.

History

It was formerly regarded as a species of Boletus, but in 2014 was transferred to the newly erected genus Butyriboletus, after molecular data revealed that it is a member of the "Regius" clade (named after B. regius), quite distant from the core clade of B. edulis and closely allied species.

The Czech botanist and mycologist Josef Velenovsky (1858-1949) described this bolete and gave it the scientific name Boletus fechtneri. In 2014 American David Arora and Jonathan L. Frank classified Pale Bolete into the new genus Butyriboletus mainly based on molecular (DNA) analysis results.

The genus name Boletus comes from the Greek word bolos, meaning "lump of clay," and the new genus Butyri prefix means "buttery."

The special epithet fechtneri is in honor of the Czech mycologist František Fechtner (1883 - 1967).

Synonyms

1. Boletus fechtneri Velen., 1922

2. Boletus aestivalis Kallenbach 1927, non Paulet nec. Fr. nec Hussey

3. Boletus appendiculatus subsp. pallescens Konrad (1929), Bulletin de la Société mycologique de France, 45(1), p. 73

4. Boletus appendiculatus var. pallescens (Konrad) Kühner & Romagnesi (1953), Flore analytique des champignons supérieurs, p. 38 (nom. inval.)

5. Boletus fechtneri Velenovský (1922), Ceské houby, 4-5, p. 704

6. Boletus pallescens (Konrad) Singer (1936), Annales mycologici, edii in notitiam scientiae mycologicae universalis, 34(6), p. 424 (nom. illegit.)

7. Boletus romellii Kallenbach (1931), Die Pilze Mitteleuropas, 1, p. 13

8. Tubiporus appendiculatus var. pallescens (Konrad) Imler (1950), Bulletin de la Société mycologique de France, 66, p. 201

Photo sources:

Photo 1 - Author: Gerhard Koller (CC BY-SA 3.0)

Photo 2 - Author: GLJIVARSKO DRUSTVO NIS from Serbia (CC BY-SA 2.0)

Photo 3 - Author: GLJIVARSKO DRUSTVO NIS from Serbia (CC BY-SA 2.0)

Photo 4 - Author: Gerhard Koller (Gerhard) (CC BY-SA 3.0)

Photo 5 - Author: 2012-08-26_Boletus_fechtneri_Velenovsky_254739.jpg: (CC BY-SA 3.0)