Tuber borchii Vittad.

Leonardi, Marco, Iotti, Mirco, Mello, Antonietta, Vizzini, Alfredo, Paz-Conde, Aurelia, Trappe, James & Pacioni, Giovanni, 2021, Typification of the four most investigated and valuable truffles: Tuber aestivum Vittad., T. borchii Vittad., T. magnatum Picco and T. melanosporum Vittad., Cryptogamie, Mycologie 20 (9), pp. 149-170 : 154-160

Tuber borchii Vittad.

( Figs 2 ; 4B ; 5C, D )

Monographia Tuberacearum: 44 (1831).

MYCOBANK NUMBER. — MB 118774.

GENBANK. — MZ423174 (nrITS), MZ458418 (nr β- tubulin), MZ458422 (nrEF 1-α).

LECTOTYPE OF TUBER BORCHII VITTAD. — Vittadini 1831 tab. I (presented with the indication XX), fig. III E-F here reprinted in Fig. 2 . (here designated; MycoBank Typification number: MBT 10001893 ).

EPITYPE OF TUBER BORCHII VITTAD. — Italy. Lombardy, Varzi, Castello Oramala, sub Quercus pubescens Willd. , 6.III.2019,44°50’28”N, 9°11’32”E, twenty ascomata, leg. Stefano Seghezzi, det. Giovanni Pacioni (epi-, AQUI[AQUI10151] here designated MycoBank Typification number: MBT 10001895).

DESCRIPTION

Ascomata

Hypogeous globose, lobate or irregular, up to 7 cm in diameter, rarely larger, sometimes with a flat base without excavation, surface of peridium pubescent, whitish (FCF3CF light grayish yellow, F9E79F very soft yellow, F0B27A soft orange), yellowish-gray, ocher, brownish, sometimes with reddish spots, smooth when fully mature, still pubescent in the depressions.

Gleba

Firm from whitish (D5DBdB light grayish green, EC7063 soft red, 797D7F dark grayish blue) to ocher with reddish hues, becoming greyish or reddish-brown by maturity, with ramified-anastomoses and thin sterile veins whitish in youth. Later ochraceous or reddish, marbled with wide, anastomosing veins which arise from various places of the peridium.

Odor

Pleasant, then strongly garlic sulfurous; taste strong.

Peridium

150-600 Μm thick, exoperidium pseudoparenchymatous, 100-300 Μm thick with textura globosa, formed of swollen cells ranging from suglobose to irregularly ellipsoid 10-50 × 8-24 Μm, yellowish but strongly coloured on the surface, with walls of collenchymatic type thickened up to 4 Μm, surface with tapered hyaline thick-walled, one to three celled cystidia up to 100 Μm long, up to 8 Μm wide at the inflated base; endoperidium plectenchymatous 60-450 Μm wide with intertwined, mainly periclineal, hyaline hyphae 20-24 × 5-6 Μm, with thin walls, mixed with a few rounded cells with slightly thickened walls; sterile veins emerge from the endoperidium to penetrate the gleba from various parts of the peridium.

Asci

Globose to subglobose, 60-100 × 50-80 Μm, with walls 1-1.5 Μm to 5 Μm thick, sessile or short stalked, croziered at the foot, containing 1-4 spores.

Ascospore

Subglobose to broadly ellipsoid, Q 1.06-1.46, 20-55 × 18-42Μm excluding ornamentation, inversely proportional in size to the number of spores in the ascus, at first translucent, then becoming light yellow to yellowish brown, sometimes with a reddish hue, regularly alveolate with mostly hexagonal but sometimes rectangular or elongated alveolae numbering 4-11 along the spore length and 3-9 across the spore width, 4-10 Μm wide but usually near 7 Μm, and 3-5 Μm high.

Endosporium

Often two-layered in KOH.

Glebal

Hyphae hyaline, 4-10 × 20-32 Μm

HABITAT. — Species naturally present in all Europe to the southern Scandinavian peninsula, from Portugal to the Caucasus and Anatolia, under broadleaved and coniferous trees, mainly sandy soil, commonly from late autumn to late spring ( Ceruti et al., 2003; unpublished data)

NOMENCLATURE AND TAXONOMY

There may be a precedent synonym for this species: Tuber albidum Picco, Melethemata inauguralia: 79 (1788) [MB 227650] which however is unavailable, unpriorable, because of the sanctioned homonym Tuber albidum Fr. (1823) [MB 227428], which refers to a different species. This Fries’ taxon is difficult to identify because of its diagnosis “ verrucis exasperatum, albidum ”. Vittadini (1831: 40, Obs.II) wrote about it: ‘the whitish external color in warty Tuber is unknown to me, I suspect. So the (species) named albidum is doubtful. (Obs. II. Tuber albidum Fr. … Color externus albidus in Tuberibus muricatis mihi prorsus extraneus, suspectus. Hinc albidi nomen ambiguum.)’. Perhaps due to a ‘ lapsus calami’, Tuber albidum Fr. is a questionable species that does not even today find a match among the known species of Tuber where all the warty peridium species are black or deep brown ( Bonito et al. 2013).

Fries (1823: 291) claims to have examined a dried sample (vs, vidi siccam), but no specimen of Tuber albidum was found in the Herbarium of Fries (UPS-FRIES) or a drawing of this taxon among Fries documents.

From the Fries’ description it is understood that it could refer to Tuber aestivum and two references ( Cesalpino 1583: 613, and Micheli 1729: 221) could confirm it, while a third ( Gleditsch 1753: 257) ‘ Lycoperdon globosum , subterraneum ...’ could describe a Rhizopogon .

In this situation, the most appropriate solution is to propose the rejection of the name Tuber albidum Fr. in application of Art. 56.1 of the Shenzhen Code ( Turland et al., 2018) and a proposal will be made to that effect.

The older name Tuber albidum Picco (1788) in addition to being unavailable (Mycobank http://www.mycobank.org/ Biolomics.aspx?Table=Mycobank&Rec=28125&Fields=All) is a poorly defined and variously interpreted Tuber species that can include several whitish species such as T. maculatum Vittad. , T. rapiodorum Tul. & C.Tul. , T. dryophilum Tul. & C.Tul. and T. puberulum Berk. & Broome , etc. ( Halász et al. 2005). The previous neotypification of T. borchii proposed by Mello et al. (2000) cannot be accepted because of formal and substantive reasons: 1) presence of an existent possible lectotype [tab. I, fig.III E-F inVittadini (1831) here designated]; 2) the probable loss of the three collections indicated as ‘neotype’, lacking however of any collecting data. They were sent by Vittadini to the Tulasne brothers ( Tulasne & Tulasne 1851: 146) and preserved originally in PC (Cryptogamic Herbarium of Muséum National d’Histoire Naturelle, Paris), and later retained in TO (Mattirolo’s Herbarium); 3) the fact that the proposed neotype was not sequenced.

Hence there is a need to propose an epitype using a specimen with well-defined collection data and molecular characterization.

Bonuso et al. (2010) hypothesized the presence of two cryptic species (referred to as haplotype 1 and haplotype 2) within Italian populations of T. borchii . The T. borchii epitype designated here belongs to haplotype 1.

Figures

FIG. 2. — Table I (XX),lectotype ofTuber borchii Vittad.(red arrowed).

FIG. 4. — Ascomata of A) epitype of Tuber aestivum Vittad. (AQUI 10150);B) epitype of T.borchii Vittad.(AQUI 10151);neotype of T.magnatumVittad (TO HG3458); epitype of T. melanosporum Vittad. (AQUI 10152). Scales bars: 1 cm.

FIG. 5. — Cross sections of peridia, asci and spores A, B, Tuber aestivum epitype; C, D, T. borchii epitype; E, F, T. magnatum neotype; G, H, T. melanosporum epitype. Scales bars A, C, E, G, 50 µm; B, D, F, H, 20 µm.