Mycorrhizal fungi of the genus Tuber are classified by morphological characters that allow differentiation of most species. However, some economically important species are difficult to differentiate on morphological grounds. When morphological traits are not sufficient to discriminate between taxa, other markers are needed. Genetic variation of fruit bodies of 12 Tuber taxa was studied by the random amplified polymorphic DNA (RAPD) technique. High interspecific variability was observed between most species. Moreover, important infraspecific variation occurred in all species, except Tuber brumale s.L, Tuber melanosporum, and Tuber magnatum. Southern hybridization patterns of RAPD products of the various species were used to confirm the data. Relationships among Tuber species were determined by cluster analyses. UPGMA analyses revealed several main clusters and a low genetic similarity between taxa. These results indicate that RAPD and polymerase chain reaction are useful for analysing genetic variation within Tuber species. Most species can be identified by differences in their amplified DNA profiles. However, the two pairs of closely related taxa Tuber aestivum – Tuber uncinatum and Tuber brumale var. brumale – Tuber brumale var. moschatum did not appear to differ genotypically. Key words: Tuber, RAPD, Southern, UPGMA, inter- and infra-specific variability.

Identification of some economically important Tuber species using classical morphological characteristics is sometimes difficult. We report here the molecular characterization of a species coming from China, Tuber indicum, mistaken with Tuber melanosporum species. Using restriction analysis of the amplified internal transcribed spacer (ITS) of rDNA, ITS sequence analysis, and sequence characterized amplified region markers, with DNA from fruit bodies or mycorrhizae, genetic variation was found between these two species, allowing to differentiate and characterize them.

Resume.-L'analyse electrophoretique de certaines proteines a fonction enzymatique peut se reveler un outil interessant pour caracteriser et differencier les especes fongiques, qu'il s'agisse de Tuber ou d'autres especes. L'etude a ete realisee sur trois types de materiel fongique : ascocarpes d'origine geographique differente, cultures myceliennes et ectomycorhizes de noisetier (Cary/us ave/lana). Cinq systemes enzymatiques (MDH, PGI, GDH a NADP, SOD et ACP) ont ete testes sur gel d'amidon, gel de polyacrylamide et gel mixte (agarose-polyacrylamide). Les systemes testes (saul Ia SOD) menent en evidence chez les ascocarpes une variabilite intraspecifique importante qui pourrait permenre l'individualisation d'ecotypes. La SOD, par contre, a fourni des profils suffisamment homogenes au niveau intraspecifique mais heterogenes au niveau interspecifique pour differencier les especes majeures entre elles. Ce systeme peut done etre utilise pour !'elaboration d'une cle biochimique d'identification des truffes. La synthase des donnees isoenzymatiques par I' analyse statistique a confirme l'etroite analogie entre certains taxons proches morphologiquement (T aestivum-T. uncinatum) mais en a differencie d'autres ( T brumale-T. moschatum). Les ascocarpes et les cu~ures myceliennes qui en sont issues presentent les memes profils electrophoretiques. Seule Ia GDH a NADP a pu iHre mise en evidence dans les mycorhizes ; Ia SOD a donne des resultats plus irreguliers. Outre son interet en taxonomie, !'analyse du polymorphisme enzymatique chez les Tuber apporte un nouvel outil pour Ia caracterisation et !'identification du symbiote fongique (ascocarpes. cultures myceliennes, mycorhizes), le controle de Ia mycorhization et Ia detection dans le sol.Summary.-Electrophoretic analysis of isozymes was used to characterize and identify some Tuber species. Ascocarps, mycelial cu~ures and mycorrhizas were studied using 5 isozyme systems (MDH. GPI, NADP-GDH, SOD, ACP). Electrophoresis was carried out on starch gels, polyacrylamide gels and agarose-polyacrylamide gels. All systems (except SOD) showed a broad intraspecific variability, among ascocarps. However, SOD was homogeneous for a species but heterogeneous between different species. This system can be used to elaborate a biochemical identification key. The statistical analysis indicated a close similarity between some taxa ( T aestivum-T unclf1atum) but distinguished others ( T brumale-T moschatum). MDH. GPI, NADP-GDH and SOD patterns for ascocarps and mycelial cultures are similar. NADP-GDH was the only isozyme which could be detected in ectomycorrhizas.

No abstract