Baorangia bicolor

Description

The color of the cap is light red when young and brick red in maturity. The cap is 4–15 cm (1+1⁄2–6 in) wide, with yellow pores underneath. It is one of several types of boletes that have the unusual reaction of the pore surface producing a dark blue/indigo when 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.

The stem is 5–10 cm (2–4 in) long and 1–3 cm (3⁄8–1+1⁄8 in) thick. 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 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.

Similar species

There are several similar species and the differences are minute in most cases. Boletus sensibilis differs in that it has an immediate bruising reaction and is poisonous, causing stomach upset if ingested, and in some cases a severe allergic reaction. B. miniato-olivaceus has a full yellow stem and slightly lighter cap coloration. It also has a more immediate bruising reaction and the stem is slightly longer in proportion to the cap. B. peckii has a smaller average size, a rose red cap that turns almost brown with age, flesh that is paler in color, and a bitter taste. B. speciosus has a fully reticulated stem, more brilliant colors, and very narrow cylindrical spores.

Hortiboletus rubellus subsp. rubens is almost indistinguishable in appearance. Boletus bicoloroides is very similar, but has only been found in Michigan and has larger spores. B. bicoloroides is slightly larger, the cap around 1 cm (3⁄8 in) wider and the stem 1 cm longer. Lanmaoa pallidorosea quickly stains blue. Hortiboletus species are usually smaller.

Varieties

There are two varieties of the two-colored bolete: borealis and subreticulatus. Both varieties have a very similar habitat to that of the main species, except they appear to be limited to just the North American continent. Both varieties also have a slightly different coloration than that of the two-colored bolete, have deeper pores, and are not as often eaten or used in regional recipes.

Variety borealis

Variety borealis has a slightly darker color scheme than the main species. The coloration in general is darker; the cap can vary from a bright apple red to a dark brick red with maturity, to almost purple in some instances. The pore surface has a varying coloration of orange red to red and becoming a dull brown red with age. The bruising coloration is a blue green and the spore print is olive brown. The distribution of variety borealis is relatively small, ranging from Michigan to the upper New England states. The similar distribution and coloration to Boletus carminiporus has caused the two to be confused. New molecular evidence shows that borealis is not closely related to Baorangia bicolor var. bicolor.

Variety subreticulatus

Variety subreticulatus, like variety borealis, has a generally darker coloration than the two-colored bolete, but varies much more than either. When fresh the coloration of the cap varies from a rose red, red, rose pink, dark red, and purple red. With age it changes to a cinnamon red or a rusty rose color, with yellowing toward the margin. The pore surface is similar to that of the main species—yellow when fresh and with age changing to a dull ochre yellow; the bruising coloration is blue but is much lighter and sometimes not appearing to stain when bruised at all. The spore print is olive brown. The distribution of variety subreticulatus is very similar to the distribution of the two-colored bolete in North America, and appears north to eastern Canada and south to Florida, and west to Wisconsin.

Distribution and habitat

The two-colored bolete is distributed from southeastern Canada and the Great Lakes Region, primarily east of the Rocky Mountains, as far south as the Florida peninsula, and out to the Midwest as far as Wisconsin. It is commonly found in deciduous woodland and usually grows under or close to broad-leaved trees, especially oak. It can be found in isolation and in groups or clusters, primarily during June through October. It is also found in China and Nepal. This unusual distribution is part of the Grayan disjunction, a phenomenon characterized by a species living in one continent or island and then also on the other side of the world with no specimens of the species living in between the specific habitats. The Grayan disjunction is not uncommon among fungi.

Edibility

The two-colored bolete is an edible mushroom, although some may have an allergic reaction after ingestion that results in stomach upset. The mushroom has a very mild to no taste. It can be cooked several ways and the varying color of the cap can be used to determine if the mushroom is ready to be eaten. Less mature caps are lighter red and are often larva infested and/or soft fleshed. Mature, safe-to-eat caps have a dark brick red color. Drying the two-colored bolete is a good method for storage. The time it takes to bruise when identifying the species for consumption; the mushroom should take several minutes to bruise compared to the instant bruising of the poisonous B. sensibilis.

It is one of the most used mushrooms of over 200 species of edible mushrooms used in Nepal.