Data from: How the truffle got its mate: insights from genetic structure in spontaneous and planted Mediterranean populations of Tuber melanosporum

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
versus 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.