Article: Molecular Ecology Resources

A survey of genome-wide single nucleotide polymorphisms through genome re-sequencing in the Périgord black truffle (Tuber melanosporum Vittad.)

Thibaut Payen, Claude Murat, Anaïs Gigant, Emmanuelle Morin, Stéphane De Mita and Francis Martin

Abstract

The Périgord black truffle (Tuber melanosporum Vittad.), considered a gastronomic delicacy worldwide, is an ectomycorrhizal filamentous fungus that is ecologically important in Mediterranean French, Italian, and Spanish woodlands. In this study, we developed a novel resource of single nucleotide polymorphisms (SNPs) for T. melanosporum using Illumina high-throughput re-sequencing. The genome from six T. melanosporum geographic accessions was sequenced to a depth of ~20×. These geographic accessions were selected from different populations within the northern and southern regions of the geographical species distribution. Approximately 80% of the reads for each of the six re-sequenced geographic accessions mapped against the reference T. melanosporum genome assembly, estimating the core genome size of this organism to be ~110 Mbp. A total of 442,326 SNPs corresponding to 3,540 SNPs/Mbps were identified as being included in all seven genomes. The SNPs occurred more frequently in repeated sequences (85%), although 4,501 SNPs were also identified in the coding regions of 2,587 genes. Using the ratio of non-synonymous mutations per non-synonymous site (pN) to synonymous mutations per synonymous site (pS) and Tajima’s D index scanning the whole genome, we were able to identify genomic regions and genes potentially subjected to positive or purifying selection. The SNPs identified represent a valuable resource for future population genetics and genomics studies.