title: Tuber melanosporum outcrosses: analysis of the genetic diversity within and among its natural populations under this new scenario.
abstract: Tuber melanosporum is an ectomycorrhizal ascomycete producing edible ascocarps. The prevalent view is that this species strictly selfs, since genetic analyses have never detected heterozygotic profiles in its putatively diploid/dikaryotic gleba. The selfing model has also forged the experimental approaches to assess the population genetic variability. Here, the hypothesis that T. melanosporum outcrosses was tested. To this end, SSR (simple sequence repeats) and ITS (internal transcribed spacer) markers were employed to fingerprint asci and the surrounding gleba within single ascocarps. The distribution of genetic variability was also investigated at different geographical levels using single (SSR and ITS) and multilocus (AFLP, amplified fragment length polymorphism) markers. It is shown that T. melanosporum outcrosses since asci display additional alleles besides those present in the surrounding, uniparental, gleba. Furthermore, SSR and AFLP data reveal a high rate of intrapopulation diversity within samples from the same ground and root apparatus and the highest rate of genetic variability within the southernmost populations of the distributional range. These data call for a profound re-examination of T. melanosporum mating system, life cycle and strategies for managing man-made plantations. They also strongly support the idea that the last glaciation restricted the species distribution to the Italian and Spanish peninsulas.
authors.affiliation: National Research Council, Plant Genetics Institute - Perugia, Via della Madonna Alta 130, I-06128 Perugia, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Riccioni
authors.affiliation: National Research Council, Plant Genetics Institute - Perugia, Via della Madonna Alta 130, I-06128 Perugia, Italy.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Belfiori
authors.affiliation: National Research Council, Plant Genetics Institute - Perugia, Via della Madonna Alta 130, I-06128 Perugia, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Rubini
authors.affiliation: National Research Council, Plant Genetics Institute - Perugia, Via della Madonna Alta 130, I-06128 Perugia, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Passeri
authors.affiliation: National Research Council, Plant Genetics Institute - Perugia, Via della Madonna Alta 130, I-06128 Perugia, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Arcioni
authors.affiliation: National Research Council, Plant Genetics Institute - Perugia, Via della Madonna Alta 130, I-06128 Perugia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Paolocci
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis / Q000379:methods; D001203:Ascomycota / Q000235:genetics*; D003433:Crosses, Genetic; D004271:DNA, Fungal; D021901:DNA, Intergenic; D004275:DNA, Ribosomal; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes; D007178:Inbreeding; D018598:Minisatellite Repeats; D038821:Mycorrhizae / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D012098:Reproduction / Q000235:genetics
chemical_list: D004271:DNA, Fungal; D021901:DNA, Intergenic; D004275:DNA, Ribosomal