Butyriboletus fechtneri: The Ultimate Mushroom Guide
About The Butyriboletus fechtneri Mushroom
Butyriboletus fechtneri is a basidiomycete fungus in the family Boletaceae. Fruitbody large to medium-sized, boletoid, without veil and ring. Stipe solid, with a surface usually covered with granules or network. Flesh variously colored, changing or not when exposed to air. Tubes easily separable from each other, not tearing apart. Pores usually small and rounded.
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.
This mushroom 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).
Other names: Pale Bolete.
Butyriboletus fechtneri Identification
Ranging from 8 to 20cm in diameter, the cap of Butyriboletus fechtneri is greyish to silvery white and velvety at first, darkening and sometimes having an olivaceous or slightly pinkish tinge towards the margin. Young fruitbodies have rounded and domed caps, but with age, they often develop slightly irregularly.
When cut, the yellow flesh of Butyriboletus fechtneri turns blue, most strongly in the region of the cap.
Tubes and Pores
The tubes of the Pale Bolete Boletus fechtneri are very small and initially lemon yellow, becoming deeper yellow before eventually developing an olivaceous tinge. When exposed to the air the tubes turn blue, as also do the tiny yellow pores if they are bruised.
The stipe of Butyriboletus fechtneri is usually clavate (club shaped, as seen on the left) or occasionally cylindrical, sometimes tapering rapidly towards the base.
Pale lemon yellow over its lower two-thirds or so, the stem surface is more deeply yellow near the apex. Occasionally there is a pink or red-brown central zone, covered with very faint fine reticule (network). As with the rest of this bolete, the stem surface turns blue when bruised. Inside the stem the flesh is yellowish-white, becoming more of a pinkish-brown towards the base.
Subfusiform, 9-15 x 4-6µm.
Odor and taste
Young specimens have a mild taste and no distinctive odor.
Butyriboletus fechtneri Look-Alikes
Has a chalky white cap, red pores and a bulbous red stem.
Has a pale cap and yellow pores; its stem is yellow towards the apex and red towards the base.
Butyriboletus fechtneri Taxonomy & Etymology
This bolete was priginally named and described by the famous Czech botanist and mycologist Josef Velenovsky (1858-1949), who gave it the scientific name Boletus fechtneri. In 2014, Americans David Arora and Jonathan L. Frank transferred the Pale Bolete to the new genus Butyriboletus, based largely on the results of molecular (DNA) analysis which has prompted a major revision of the family Boletaceae.
Common synonyms of Butyriboletus fechtneri include Boletus fechtneri Velen., Boletus appendiculatus ssp. pallescens Konrad, Bull., and Boletus pallescens (Konrad) Singer.
The generic name Boletus comes from the Greek bolos, meaning 'lump of clay', while the Butyri- prefix to the new genus means 'buttery'. The specific epithet fechtneri honors the Czech mycologist František Fechtner (1883 - 1967).
Butyriboletus fechtneri profile
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