Cacaoporus Raspe & Vadthanarat

Vadthanarat, Santhiti, Lumyong, Saisamorn & Raspe, Olivier, 2019, Cacaoporus, a new Boletaceae genus, with two new species from Thailand, MycoKeys 54, pp. 1-29 : 1

Cacaoporus Raspe & Vadthanarat gen. nov.

Etymology.

Refers to the dark, chocolate brown hymenophore and overall colour of basidiomata.

Diagnosis.

Similar to the genus Sutorius in having brown basidiomata with brown encrustations in the flesh but differs from Sutorius in having the following combination of characters: brown to chocolate brown or greyish-brown to dark brown or blackish-brown basidiomata, without violet tinge, chocolate brown to dark brown hymenophore, tubes not separable from the pileus context, white to off-white basal mycelium which turns reddish-white to pale red when bruised, amygdaliform to ovoid with subacute apex in side view to ovoid basidiospores and dark brown spore deposit.

Description.

Basidiomata stipitate-pileate with poroid hymenophore, small to medium-sized, dull, brown to greyish-brown to dark brown or blackish-brown. Pileus convex when young becoming plano-convex to slightly depressed with age, with deflexed to inflexed margin; surface even to subrugulose, minutely tomentose or slightly cracked at the centre; context soft, yellowish to greyish off-white then slightly greyish-orange to dull orange to greyish-brown when exposed to the air, patchy or marmorated with greyish-brown to dark brown, sometimes with scattered small dark brown to brownish-black encrustations, not or inconsistently reddening when cut. Hymenophore tubulate, adnate, subventricose to ventricose, slightly depressed around the stipe; tubes brown to greyish-brown to dark brown, not separable from the pileus context; pores regularly arranged, mostly roundish at first becoming slightly angular with age, sometimes irregular, elongated around the stipe, dark brown to greyish-brown at first, becoming brown to chocolate brown with age. Stipe central, terete to sometimes slightly compressed, cylindrical to sometimes slightly wider at the base; surface even, minutely tomentose, dull, dark brown to greyish-brown, basal mycelium white to off-white becoming reddish-white to pale red when touched; context solid, yellowish to orange white to yellowish-grey to pale orange to dull orange to reddish-grey, marmorated or virgated with brownish-grey to greyish-brown to dark brown, sometimes scattered with small reddish-brown to brownish-black fine encrustations, unchanged or inconsistently reddening when cut. Spore print dark brown.

Basidiospores amygdaliform to ovoid or ovoid with subacute apex in side view, thin-walled, smooth, slightly reddish to brownish hyaline in water, slightly yellowish to greenish hyaline in KOH or NH4OH, inamyloid. Basidia 4-spored, clavate to narrowly clavate without basal clamp connection. Cheilocystidia fusiform or cylindrical with obtuse apex, sometimes bent or sinuate, thin-walled, often scattered with small brownish-yellow to yellowish-brown crystals on the walls in KOH or NH4OH. Pleurocystidia narrowly fusiform with obtuse apex or cylindrical to narrowly subclavate, sometimes bent or sinuate, thin-walled, densely covered with small reddish-brown to brownish dark encrustations on the walls when observed in H2O, which are discoloured then dissolved in KOH or NH4OH. Pileipellis a trichoderm becoming tangled trichoderm to tomentum, composed of thin-walled hyphae; terminal cells mostly slightly sinuate cylindrical to irregular with rounded apex or clavate to elongated clavate. Stipitipellis a trichoderm to tangled trichoderm or disrupted hymeniderm, composed of loosely to moderately interwoven cylindrical hyphae anastomosing at places. Clamp connections not seen in any tissue.

Typus generis.

Cacaoporus tenebrosus

Distribution.

Currently known from Thailand.

Notes.

Sutorius most closely resembles the new genus. In the field, Cacaoporus is easily distinguished from the Sutorius by the following combination of characters: chocolate brown to dark brown to blackish-brown basidiomata, which are darker than in Sutorius and never purplish-brown like in Sutorius species; chocolate brown to dark brown hymenophore, which is much darker than in Sutorius and never reddish- to purplish-brown like in Sutorius ; tubes that are not separable from the pileus context but can be separated in Sutorius ; off-white basal mycelium that more or less turns red when bruised, which is never the case in Sutorius .