Fruit body of the Bay Bolet (Xerocomus badius). Photo credit : Francis Martin, INRA.

Within the framework of the Mycorrhizal Genomics Initiative (MGI), we are sequencing a phylogenetically and ecologically diverse suite of mycorrhizal fungi, which include the major clades of symbiotic species associating with plants. Analyses of these genomes will provide insights into the diversity of mechanisms for the mycorrhizal symbiosis, including arbuscular, ericoid-, orchid- and ectomycorrhizal associations.

The Bay Bolet Xerocomus badius
The porcini Xerocomus badius (Fr.) Kühn. syn. Boletus badius Fr., commonly known as the bay bolete, is a conspicuous wild, edible mushroom characterized by fleshy fruiting bodies with a poroid hymenophore. It is found on the ground or on decaying tree stumps in coniferous or mixed forests of Europe and North America. Although the bay bolete is predominantly an ectomycorrhizal mutualist, it is thought to have some saprobic abilities.

Genetic analysis published in 2013 shows that Xerocomus (Boletus) badius is taxonomically-related to B. pallidus and B. glabellus; the three species form a clade known informally as the badius clade in the suborder Boletineae. A molecular clock analysis dates the origin of porcini to between 42 and 54 million years ago, coinciding with the initial diversification of angiosperms, during the Eocene epoch when the climate was warm and humid.

Several genomes of saprotrophic and ectomycorrhizal Boletales have been produced by the MGI, including Boletus edulis, Suillus luteus, Gyrodon lividus, Paxillus involutus, P. rubicundulus and Coniophora puteana. The genome of Xerocomus badius will provide glimpse into the Boletales evolution.

The MGI is a large collaborative effort led by Francis Martin (INRA) aiming for master publication(s) describing the evolution of the mycorrhizal symbioses. Researchers who wish to publish analyses using data from unpublished MGI genomes are respectfully required to contact the PIs and JGI to avoid potential conflicts on data use and coordinate other publications with the MGI master paper(s).