Phylogenetic relationships among truffle species from Europe and China were investigated through parsimony analysis of the ITS sequences. Three major clades were obtained among the species analysed. The so-called white truffles appeared polyphyletic since Tuber magnatum was grouped with brown truffles and not with the other white species (T. maculatum, T. borchii, T. dryophilum, T. puberulum). The black truffles investigated in this study, T. brumale, T. melanosporum, T. indicum and T. himalayense, were grouped in an independent clade. The Périgord black truffle T. melanosporum and the Chinese black truffles T. indicum and T. himalayense, were very closely related. The delimitation of these species was estimated by a distance analysis on several isolates collected from different geographic areas. In spite of intraspecific variations of the internal transcribed spacers (ITS) sequences, T. melanosporum and the Chinese black truffles can be unambiguously attributed to distinct taxa.
Requ le 22 mai 198 1 PARGUEY-LEDUC, A . , et M. C. JANEX-FAVRE. 1982. La paroi des asques chez les PyrCnomycetes: ktude ultrastructurale.I. Les asques bituniquks typiques. Can. J. Bot. 60: 1222-1230. Dans les asques bituniquks typiques des Pyrknomycktes, la paroi prksente une organisation homogkne et complexe. D'abord unituniquke, elle devient rapidement bituniquke; les deux tuniques (exoascus et endoascus) sont ensuite sCparCes par un espace clair consCcutif i la lyse de la partie externe de l'endoascus. A l'ktat adulte, l'exoascus comporte deux couches superposCes, alors que l'endoascus, form6 d'une couche unique, prksente une disposition remarquable de ses fibrilles, plissCes en accordkon.La structure de la paroi des asques bituniquCs parait donc essentiellement caractCrisCe, tant chez les PyrCnomycktes que chez les Discomycktes, lichknisants ou non, par la prCsence de deux tuniques dont l'interne (endoascus) montre une structure fibrilleuse ondulee ou plissCe. Cette structure est toutefois beaucoup plus nette chez les Pyrknomycktes. De plus, chez ces derniers, l'exoascus et l'endoascus sont toujours sCparCs l'un de l'autre par un espace clair.
PARGUEY-LEDUC,A . , and M. C. JANEX-FAVRE. 1982. La paroi des asques chez les Pyrknomycktes: Ctude ultrastructurale.I. Les asques bituniquks typiques. Can. J. Bot. 60: 1222-1230. A complex and homogeneous organization is present in the ascus wall of typical bitunicate Pyrenomycetes. First unitunicate, the wall soon becomes bitunicate. A clear space then separates both tunicae (exoascus and endoascus); it is formed by the lysis of the external part of the endoascus. In the mature ascus the exoascus is composed of two superposed layers and the endoascus of a single layer which shows remarkable accordion-like fibrillas.The essential structural feature of the bitunicate ascus wall is the presence, in the Pyrenomycetes as well as in lichenized and nonlichenized Discomycetes, of two tunicae, the inner (endoascus) presenting a wavy or folded fibrillar structure. In the Pyrenomycetes such a structure is much more distinct, however; a clear space in addition separates the exoascus and the endoascus.
In Tuber melanosporum, as in a few other truffles (genus Tuber), ultrastructural observations show that each ascospore is delimited in the ascus apical zone through an individual process, the single primordial wall originating from a lomasomic extension. The primordial wall splits into two layers (primary wall), then a secondary part is deposited. At the most complex stage it comprises, from interior to exterior: a regular clear epispore; a dark exospore producing ornamental spines; a clear perispore which strongly dilates then shrinks around each spine; a limiting ectospore. In the mature ascospore, the ascospore wall is composed of only two superimposed parts corresponding to the two ascospore walls visible with light microscope. The clear internal part is the epispore and the brown echinulate external one represents the joined exospore, perispore, and ectospore. The ascospores contain six to eight early formed nuclei and cytoplasmic inclusions. Mitochondria prevail in young ascospores whereas oil droplets nearly fill the mature ones.
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