Armillaria mellea [Photo credit: László Nagy]

This genome was sequenced as part of the JGI CSP "1000 Fungal Genomes – Deep Sequencing of Ecologically-relevant Dikarya" project. Within the framework of this project, we are sequencing keystone lineages of saprophytic, mycorrhizal, and endophytic fungi that are of special ecological importance. Dozens of sequenced species were harvested from Long Term Observatories to serve as the foundation for a reference database for metagenomics of fungi and for a comprehensive survey of the soil fungal metatranscriptome.

Armillaria mellea ELDO17

Members of the genus Armillaria belong to the Physalacriaceae, a highly diverse family in the Agaricales containing white rot wood decayers and devastating tree pathogens. They cause shoestring root rot, which lead to significant losses in forest areas or woody plants, including forests, parks or vineyards, among others, mostly in the temperate zone. The infection is usually characterized by presence of rhizomorphs and mycelial mats between the bark and cambium layer of the host root. Rhizomorphs are shoestring-like multicellular structures, which are analogous to plant roots in appearance and forage for food by spreading inside the soil. Armillaria spp. produce macroscopic fruiting bodies that are edible and known as honey mushrooms. Many existing individuals of Armillaria are believed to be the largest and oldest terrestrial organisms known on earth.

We aim to sequence the genomes of several Armillaria strains with lifestyles ranging from aggressive pathogens to white-rot saprotrophs. This will allow us to gain insights into the evolution of pathogenicity and the mechanisms of interaction between Armillaria and their host trees. It will further help understanding the biology of these species, including their strategies for host invasion, for wood decay, and the development of rhizomorphs and fruiting bodies. We hope these resources will open the door for developing efficient management strategies for limiting the spread and damage to forest ecosystems.

Armillaria mellea is the most intensely researched Armillaria species. In nature, it is common and widespread across Europe, Britain, Ireland and also in many other parts of the world including North America, Africa and Asia. The species can either be homothallic (as found across Japan and Africa); or heterothallic (found across Europe and North America); however, the strain sequenced is a heterothallic isolate ELDO17 collected from the western US. A. mellea is an aggressive pathogen in temperate forests. It is known to cause root rot disease in a wide range of hosts, where it is found as clumped clusters at the base of living or dead trees. Apart from its pathogenic potential, A. mellea has also been reported to form symbiotic relationships with members of Orchidaceae (e.g. Gastrodia elata) by engaging in energy metabolism and tuber growth.

The 1KFG project is a large collaborative effort aiming for master publication(s). Please do contact the PI for 1KFG - Deep Sequencing of Ecologically-relevant Dikarya (Dr. Francis Martin) for permission prior to the use of any data in publications.