Tuberaztecorum sp. nov., a truffle species from Mexico belonging to the Maculatum clade (Tuberaceae, Pezizales) Author Guevara-Guerrero, Gonzalo Author Bonito, Gregory Author Smith, Matthew E. Author Healy, Rosanne Author II, Arthur C. Grupe Author Cazares, Efren Author Castellano, Michael A. Author Trappe, James M. text MycoKeys 2018 30 61 72 http://dx.doi.org/10.3897/mycokeys.30.22887 journal article http://dx.doi.org/10.3897/mycokeys.30.22887 1314-4049--61 Tuber aztecorum Guevara, Bonito & Smith sp. nov. Figs 1, 2 A-I Type. MEXICO. State of Mexico, Toluca-Temascaltepec road, La Puerta, Parque Nacional Nevado de Toluca, 29 July 2010, Guevara 993 (ITCV [ Jose Castillo Tovar herbarium] - holotype, MSU and FLAS - isotypes), GB KY271791. Diagnosis. Tuber aztecorum is a sister species to T. castilloi , but T. castilloi differs by having larger spores, 27-63 x 20-40 µm , is without an irregular thickness to the cell wall on peridial hyphae and is associated mainly with Quercus spp. Also resembles T. guevarai but T. guevarai has narrow spores that are 18-55 x 16-42 µm and cream-yellow fruiting bodies and rDNA variation. Etymology. "aztecorum" in reference to the ancient Aztec civilisation of Mexico. Description. Ascomata 5-23 x 4-16 x 3-11 mm, subglobose, irregular, lobate or globose, light to orange brown or reddish-brown changing to dark brown when handled, finely verrucose or granulose, with 5-8 verrucae in 1 mm, solid, brittle, surface dry, base sessile. Peridium in cross-section undetachable <.5 mm wide, with one or several basal white to cream furrows or depressions that merge into veins. 5% KOH negative. Gleba marbled, white to greyish, white veins, some veins ending in the peridium. Odour fungoid to raw potato-like, taste not recorded. Peridium 110-350 µm thick. Outer layer (epicutis) a pseudoparenchyma 62-250 µm thick, of hyphae 5-30 µm diam., versiform, angular or isodiametric, in some areas hyphae arranged perpendicular to the epicutis, hyaline to reddish-brown in mass in KOH, thick-walled (2 µm ), without intracellular content. Surface hairs versiform, single hair-like hyphae or cystidia 53-97 µm long x 4-5 µm at the base, tapered to the tip, some with septa, scattered or in clusters, brittle, thin-walled, hyaline in KOH. Other hyphae present are claviform, erect, cylindrical or sinuate with an irregular thickness to the cell wall that resembles knobs or "spines" . Some globose or constricted hyphae emerging from isodiametric hyphae, 3-10 µm wide. Inner layer (subcutis) 50-225 µm thick, of prostrate and interwoven, hyphae gradually intermixing into gleba, hyaline in KOH and trypan blue, hyphae 2 -5 µm wide. Some young specimens show noticeable prostrate cylindrical, claviform or vermiform hyphae along the subcutis that are thick-walled. Veins formed by hyaline, thin-walled, interwoven hyphae. Ascospores subglobose, globose to broadly ellipsoid, 23-58 x 18-48 µm without ornamentation, alveoli 2-7 µm tall, 7-10 alveolar meshes along the spore length, 5-6 across, polygonal (4-6 sides), cell wall 2-3 µm thick. 1-spored asci have spores that are 42-58 x 27-48 µm , 2-spored asci have spores that are 25-52 x 23-40 µm , 3-spored asci have spores that are 27-40 x 20-30 µm , 4-spored asci have spores that are 23-38 x 18-28 µm , 5-spored asci have spores that are 25-32 x 18-25 µm , yellowish to light brown in KOH and Melzer's reagent. Asci globose, subglobose to broadly ellipsoid, without pedicel, 62-95 x 57-77 mm, hyaline in KOH, yellowish to brownish in Melzer's reagent, thin-walled (immature asci thick-walled, up to 7.5 µm thick). Figure 1. Phylogenetic tree inferred under the maximum-likelihood (ML) criterion from the ITS rDNA alignment corresponding to the Tuber dataset. The tree was rooted using midpoint rooting. Numbers on the branches represent support values from 1,000 ML bootstrap replicates. The branches are scaled in terms of the expected number of substitutions per site. The phylogeny is rooted with species belonging to the Latisporum clade. Accession numbers in the sequence labels indicate sequences from Genbank. Figure 2. a-i Tuber aztecorum (holotype ITCV 993). a; Two ascomata showing the peridial surface (bar = 1 cm) b Ascoma in cross-section showing peridial surface and glebal surface (bar = 1 cm) c Peridial surface magnified showing the verrucose surface (bar = 1 mm) d Clusters of erect hyphae emanating from the peridial surface (bar =10 µm ) e A single surface hair-like hypha (bar = 10 µm ) f Cystidium (bar = 10 µm ) g Cross section of peridium showing pseudoparenchyma-like epicutis (bar = 20 µm ) h Ascospores within asci in surface view showing the alveoli (bar = 20 µm ) i Ascospore within asci in surface view showing the alveoli magnified (bar = 20 µm ). Distribution and Ecology. MEXICO, state of Mexico La Puerta, National Park Nevado de Toluca. Hypogeous, gregarious in volcanic rock soil in an Abies religiosa forest at 3065 m. N 19°11.662', W099°48.537'. 29 July 2010. Additional collections examined. Mexico, state of Mexico, La Puerta, National Park Nevado de Toluca, Guevara 1109 (paratype ITCV1109, GB KY271790), Guevara 1110 (paratype ITCV 1110), 29 July 2010.