Tuber magnatum Picco, 1788

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 : 160-161

Tuber magnatum Picco

( Figs 4C ; 5E, F )

Melethemata inauguralia: 79 (1788).

Tuber griseum Borch ex Pers. , Synopsis Methodica Fungorum: 127 (1801); sanct. Fr., Systema Mycologicum 2 (2): 292 (1823). (MB 179335).

MYCOBANK NUMBER. — MB 184470.

GENBANK. — MZ423175 (nrITS), MZ458419 (nr β- tubulin), MZ458423 (nrEF 1-α).

NEOTYPE OF TUBER MAGNATUM PICCO. — Italy. Piedmont, Montechiaro D’Asti, Loc. Seria, 45°00’30”N, 8°06’45”E, lowland grove with Quercus robur L. and Populus tremula L., under Q. robur , 29.IX.2019, four ascomata, leg. Pino Panzini, det. Alfredo Vizzini (neo-, TO[HG3458] here designated; MycoBank Typification number: MBT 10001896).

DESCRIPTION

Ascomata

Hypogeous, globose to lobate or flat, up to 10-15 cm broad and more rarely with a detachable basal mycelial cluster.Peridium whitish (FFFFF0 ivory), yellowish, pale ocher (FFD700 gold, DAA520 goldenrod) more or less greyish (DCDCDC gainsboro, D3D3D3 light gray) sometimes with greenish or reddish hues; smooth surface finely grainy under a lens.

Gleba

Whitish (FFFFF0 ivory), yellowish or pale ocher, brownish (8B4513 saddle brown, A0522D sienna, F2F2F2) with greyish tones, often with reddish purple spots; veins thin, whitish, branched, anastomosing, sometimes forming white gangliform thickenings.

Odor

Pleasant, penetrating, of garlic or strong cheese; taste pleasant.

Peridium

200-500 Μm thick, entirely pseudoparenchymatous basically of globular cells; exoperidium 80-110 Μm in the outer layer with globose cells having walls up to 4 Μm thick and slightly yellow; peridial surface with infrequent stocky, cylindrical-clavate dermatocystidia 14-20 × 8-10Μm; endoperidium 120-380 Μm thick, of thin-walled globose and polygonal cells 6.0-36 × 6-23 Μm with rare cylindrical cells 6-9 × 14-20 Μm.

Asci

Globose, short-stalked or sessile, 60-90 × 40-70Μm ( Fig. 2F ), with walls up to 4 Μm thick and a basal crozier, containing 1-4 spores.

Ascospores

Alveolate, globose to broadly ellipsoid, Q 1.05-1.33, 20-50 × 15-42 Μm excluding ornamentation, inversely proportional in size to the number of spores in the ascus, yellowish, pale ocher or sometimes light yellow-brown; reticulum with 1-3 regular or coarsely irregular, 3-6 sided alveoli 10-22 Μm wide and 4-5 (-8) Μm high, sometimes with ridges within the alveolae.

Endosporium

Often two-layered in KOH.

Glebal

Hyphae hyaline, 4-8 Μm broad, in the external veins with cylindrical or clavate-elongated cells mixed with subglobose cells 5-42 × 4-16 Μm.

HABITAT. — moist (mesophilic) woods mainly with broad-leaved trees and conifers such as Abies alba Mill. , on sandy-silty soils in southern Europe ( Italy and a few neighbouring French and Swiss areas, the Balkan-Pannonia region, Northern Anatolia), from late summer to early winter ( Belfiori et al. 2020; unpublished data). It has also been reported in Thailand, but vouchers have not been made available (Suwannarach et al., 2017).

NOMENCLATURE AND TAXONOMY

The name most frequently used for this species is Tuber magnatum Picco (1788) for which a neotype is herein designated. However, a competing name exists, namely Tuber griseum Borch ex Pers. , validated by Persoon (1801) and sanctioned by Fries (1823), for which a lectotype and epitype are also herein designated. The epitype is represented by a T. magnatum with a greyish peridium.

Borch’s or Picco’s authentic specimens were not available for either T. griseum or T. magnatum .

LECTOTYPE OF TUBER GRISEUM . — Truffe grise De Borch, Lettres sur les Truffes du Piémont, 1 st figure (1780); here reprinted in Appendix 4 (here designated; MycoBank Typification number: MBT 10001897).

EPITYPE OF TUBER GRISEUM . — Italy. Piedmont, Monte Magno, 44°59’02”N, 8°19’35”E, under Quercus robur , 07.XII.1998, one fragment, leg. Virgilio Gavazza, det. Alfredo Vizzini (epi-, TO [HG 3557] here designated; MycoBank Typification number: MBT 10001898).

A proposal will be written to conserve the name T. magnatum and reject the sanctioned name T. griseum .

Figures

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.

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

APPENDIX 4. — Lectotype ofTuber griseum Borch ex Pers.sanct.Fries (1823),“Truffe grise” De Borch (1780 1st figure).