Amylotrama Bloomfield, Davoodian, Trappe & T. Lebel, in Lebel et al., Swainsona 36: 35 (2022)
Etymology: The genus name refers to the amyloid reaction of the trama in Melzer’s reagent
Diagnosis: Basidiomata subglobose, vaguely reniform, to irregular, 20–35 mm diam., 11–20 mm high; surface dry, cream to yellow to dull or dingy yellow, with either thin filamentous dark patches or gray rough patches; at times with rhizoids or basal attachment. Hymenophore cream to dull yellow to yellow to gray, at times oozing a clear liquid; loculate with chambers 2–4 mm wide, chambers may be more compressed towards the pileipellis. Columella present or absent; if present, white.
Basidiospores statismosporic, hyaline to yellowish, subglobose to subovate, 6.5–10 ×4.5–7.2 µm, inamyloid, sometimes displaying oily inclusions. Hymenophoral trama hyaline to yellowish, amyloid in Melzer’s reagent. Pileipellis a thin cutis of dark yellow hyphae overlying a context composed of tangled, hyaline to pale yellow hyphae. Clamp connections absent in all tissues.
Index Fungorum number: IF832357
Type species: Amylotrama clelandii (G. Cunn.) Bloomfield, Davoodian, Trappe & T. Lebel, in Lebel et al., Swainsona 36: 36 (2022)
Notes: The name “Amylotrama” appears in herbaria and various publications as a provisional name applied to a polyphyletic assemblage of sequestrate boletoid fungi, with amyloid hymenophoral and/or pileal context trama in Melzer’s reagent. The name Amylotrama was introduced, restricting it to one of the monophyletic clades, and describing two species based on morphological and DNA data (Fig. 2). BLAST searches of TEF1-α, ITS and LSU and phylogenetic analyses of the loci singly and concatenated strongly supported placement of Amylotrama in the Xerocomoideae. The portions of ITS sequences retrieved were insufficient to discriminate between species within Amylotrama, however they suggested subfamily placement in Xerocomoideae, with BLAST searches matching several Xerocomoideae sequences lodged in GenBank at 92–95% (e.g. GenBank: KP012700, Hemileccinum sp. from northern Australia; MF686530, Heimioporus betula from U.S.A.). Thus far, ITS sequences had not matched any sequences from root tips based on searches of GenBank and UNITE, though 97–98% matches have been detected in Australian soil metagenomic ITS1 data (Davoodian et al. 2020). Amylotrama is the only sequestrate member of the Xerocomoideae described from Australia thus far, and the sequestrate habit is uncommon worldwide in this subfamily (Trappe & Castellano 2000).
Morphologically, Amylotrama exhibits coloration and general appearance more or less consistent with other Xerocomoideae, however no other Xerocomoideae exhibits amyloid trama. A direct comparison is difficult to make since almost all known Xerocomoideae are epigeous bolete mushrooms. Gastroboletus vividus Trappe & Castellano, a hypogeous to subhypogeous bolete with sequestrate basidiomes that occurs in the western United States, may be in Xerocomoideae based on our preliminary analysis of one LSU sequence (GenBank: KF030245).
Amylotrama can be distinguished from other Australian boletoid sequestrate genera by the combination of small basidiomata, cream to yellow to gray hymenophore, amyloid trama, and inamyloid subglobose to subovate spores.
Amylotrama banrockensis Bloomfield, Davoodian & T. Lebel 2022
Amylotrama clelandii (G. Cunn.) Bloomfield, Davoodian, Trappe & T. Lebel 2022
Lebel T, Davoodian N, Bloomfield MC, Syme K, May TW, Hosaka K, Castellano MA. 2022. A mixed bag of sequestrate fungi from five different families: Boletaceae, Russulaceae, Psathyrellaceae, Strophariaceae, and Hysterangiaceae. Swainsona. 36, 33–65.