title: How the truffle got its mate: insights from genetic structure in spontaneous and planted Mediterranean populations of Tuber melanosporum.
abstract: The life cycles and dispersal of edible fungi are still poorly known, thus limiting our understanding of their evolution and domestication. The prized Tuber melanosporum produces fruitbodies (fleshy organs where meiospores mature) gathered in natural, spontaneously inoculated forests or harvested in plantations of nursery-inoculated trees. Yet, how fruitbodies are formed remains unclear, thus limiting yields, and how current domestication attempts affect population genetic structure is overlooked. Fruitbodies result from mating between two haploid individuals: the maternal parent forms the flesh and the meiospores, while the paternal parent only contributes to the meiospores. We analyzed the genetic diversity of T. melanosporum comparatively in spontaneous forests vs. plantations, using SSR polymorphism of 950 samples from South-East France. All populations displayed strong genetic isolation by distance at the metric scale, possibly due to animal dispersal, meiospore persistence in soil, and/or exclusion of unrelated individuals by vegetative incompatibility. High inbreeding was consistently found, suggesting that parents often develop from meiospores produced by the same fruitbody. Unlike maternal genotypes, paternal mycelia contributed to few fruitbodies each, did not persist over years, and were undetectable on tree mycorrhizae. Thus, we postulate that germlings from the soil spore bank act as paternal partners. Paternal genetic diversity and outbreeding were higher in plantations than in spontaneous truffle-grounds, perhaps because truffle growers disperse fruitbodies to maintain inoculation in plantations. However, planted and spontaneous populations were not genetically isolated, so that T. melanosporum illustrates an early step of domestication where genetic structure remains little affected.
authors.affiliation: CEFE UMR 5175, CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE, 1919 route de Mende, Montpellier, 34293, France.|Institut de Systématique, Évolution, Biodiversité (ISYEB - UMR 7205 - CNRS, MNHN, UPMC, EPHE), Muséum National d'Histoire Naturelle, Sorbonne Universités, 57 rue Cuvier (CP50), Paris, 75005, France.
authors.forename: E
authors.initials: E
authors.lastname: Taschen
authors.affiliation: Institut des Sciences de l'Evolution, Université de Montpellier, CNRS, IRD, EPHE CC 065, Place Eugène Bataillon, Montpellier, 34095, France.
authors.forename: F
authors.initials: F
authors.lastname: Rousset
authors.affiliation: CEFE UMR 5175, CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE, 1919 route de Mende, Montpellier, 34293, France.
authors.forename: M
authors.initials: M
authors.lastname: Sauve
authors.affiliation: CEFE UMR 5175, CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE, 1919 route de Mende, Montpellier, 34293, France.
authors.forename: L
authors.initials: L
authors.lastname: Benoit
authors.affiliation: CEFE UMR 5175, CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE, 1919 route de Mende, Montpellier, 34293, France.
authors.forename: M-P
authors.initials: MP
authors.lastname: Dubois
authors.affiliation: CEFE UMR 5175, CNRS - Université de Montpellier - Université Paul-Valéry Montpellier - EPHE, 1919 route de Mende, Montpellier, 34293, France.
authors.forename: F
authors.initials: F
authors.lastname: Richard
authors.affiliation: Institut de Systématique, Évolution, Biodiversité (ISYEB - UMR 7205 - CNRS, MNHN, UPMC, EPHE), Muséum National d'Histoire Naturelle, Sorbonne Universités, 57 rue Cuvier (CP50), Paris, 75005, France.|Department of Plant Taxonomy and Nature Conservation, University of Gdansk, Wita Stwosza 59, Gdansk, 80-308, Poland.
authors.forename: M-A
authors.initials: MA
authors.lastname: Selosse
mesh_terms: D001203:Ascomycota / Q000235:genetics*; D065928:Forests; D005602:France; D014644:Genetic Variation; D005828:Genetics, Population; D018895:Microsatellite Repeats; D038821:Mycorrhizae; D012988:Soil Microbiology
keywords: dispersal; domestication; ectomycorrhizae; hermaphroditism; hypogeous fungi; inbreeding