Baorangia bicolor, also known as the two-colored bolete or red and yellow bolete after its two-tone coloring scheme of red and yellow, is an edible fungus in the genus Baorangia. It inhabits most of eastern North America, primarily east of the Rocky Mountains and in season during the summer and fall months but can be found across the globe in China and Nepal. Its fruit body, the mushroom, is classed as medium or large in size, which helps distinguish it from the many similar appearing species that have a smaller stature. A deep blue/indigo bruising of the pore surface and a less dramatic bruising coloration change in the stem over a period of several minutes are identifying characteristics that distinguish it from the similar poisonous species Boletus sensibilis. There are two variations of this species, variety borealis and variety subreticulatus, and several other similar species of fungi are not poisonous.
Taxonomy and naming
Baorangia bicolor was originally named in 1807 by the Italian botanist Giuseppe Raddi. American mycologist Charles Horton Peck named a species collected in Sandlake, New York, in 1870, Boletus bicolor. Although this naming is considered illegitimate due to article 53.1 of the International Code of Botanical Nomenclature, Peck is still given as the authority in the Bessette et al. (2000) monograph of North American boletes. Boletus bicolor (Raddi) is not a synonym of "Boletus bicolor" Peck. Peck's Boletus bicolor describes the Eastern North American species that is the familiar "two-colored bolete", while Raddi's Boletus bicolor describes a separate European species that is lost to science. This taxonomic conflict has yet to be resolved. In 1909 a species found in Singapore was named Boletus bicolor by George Edward Massee; this naming is illegitimate and is synonymous with Boletochaete bicolor according to Singer. Molecular studies found that Boletus bicolor was not closely related to the type species of Boletus, Boletus edulis, and in 2015 Alfredo Vizzini transferred Boletus bicolor to the genus Baorangia. The original botanical name for this two-colored bolete was derived from the Latin words bōlētus, meaning "mushroom", and bicolor, meaning "having two colors."
Description
The color of the cap of the two-colored bolete varies from light red and almost pink to brick red. The most common coloration is brick red when mature. The cap usually ranges from to in width, with bright yellow pores underneath. The two-colored bolete is one of several types of boletes that have the unusual reaction of the pore surface producing a dark blue/indigo when it is injured, although the reaction is slower than with other bluing boletes. When the flesh is exposed it also turns a dark blue, but less dramatically than the pore surface. Young fruit bodies have bright yellow pore surfacesthat slowly turn a dingy yellow in maturity.
The stem of the two-colored bolete ranges from to in length and ranges from to in width. The stem coloration is yellow at the apex and a red or rosy red for the lower two thirds. When injured it bruises blue very slowly and may hardly change color at all in some cases. The stem lacks a ring and lacks a partial veil.
Microscopic characteristics
The spore deposit of the two-colored bolete is olive-brown. Viewed with a microscope, the spores are slightly oblong to ventricose in face view; in profile view, the spores are roughly inequilateral to oblong, and have a shallow suprahilar depression. The spores appear nearly hyaline (translucent) to pale dingy ochraceous when mounted in potassium hydroxide solution (KOH), have a smooth surface, and measure 8–12 by 3.5–5 μm. The tube trama is divergent and gelatinous, originates from a single central strand, not amyloid, and will often stain yellow-brown when placed in dilute potassium hydroxide (KOH).
Chemical tests
Further methods of identification are chemical tests. With the application of FeSO4 to the cap cuticle (pileipellis), it will turn a dark grey, almost black color and with the application of potassium hydroxide or NH4OH it has a negative coloration. The context stains a bluish grey to an olive green when FeSO4 is applied to it, a pale orange to a pale yellow with the application of KOH, and negative with the application of NH4OH.