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Armillaria root disease: Understanding fungal genes to determine ecological function

Date: April 15, 2015

Mycelial fan of Armillaria
White mycelial fans of Armillaria are found under the bark of infested trees.


Armillaria root disease affects diverse tree species worldwide and is a major cause of lost productivity, carbon sequestration, and other environmental benefits of forest trees. Although Armillaria species are soil fungi that occur worldwide, these fungi play different ecological roles, such as deadly root-disease pathogen or beneficial saprophyte. The expression of genes within the fungus determines its ecological role, and gene expression was determined for an Armillaria species that was causing root disease on a forest tree.


Forest fungi play many roles within forest ecosystems, including wood degradation, symbioses, disease, and biological control. Studies on gene expression of forest fungi shed light on the critical ecological roles of fungi. A recent publication led by Amy Ross-Davis (Rocky Mountain Research Station collaborator) and Jane Stewart (University of Georgia) entitled Transcriptome of an Armillaria root disease pathogen reveals candidate genes involved in host substrate utilization at the host–pathogen interface identified over 20,000 genes that were functioning in an active Armillaria root disease pathogen. This is the first study to assemble and characterize a transcriptome (set of functioning genes) of Armillaria spp.  Understanding gene expression related to disease can help develop forest management strategies to reduce disease impacts across forest landscapes. This information not only improves our understanding of the organism’s biology and ecological function, but also has other diverse applications, such as biofuel production and bioremediation of toxic sites. 

Fruiting bodies of Armillaria spp.
Fruiting bodies of Armillaria spp.


This collaborative study is a product of the Rocky Mountain Research Station/Pacific Northwest Research Station/Pacific Southwest Research Station-sponsored Western Forest Transcriptome Survey. The study included personnel from Rocky Mountain Research Station's Forest and Woodland Ecosystems Science Program (Ned Klopfenstein, John Hanna, and Geral McDonald),  Rocky Mountain Research Station Grassland, Shrubland and Desert Ecosystems Science Program (Bryce Richardson), and Pacific Northwest Research Station (Richard Cronn).




Featured Publications

Ross-Davis, Amy ; Stewart, J. E. ; Hanna, John W. ; Kim, M.-S. ; Knaus, B. J. ; Cronn, R. ; Rai, H. ; Richardson, Bryce A. ; McDonald, G. I. ; Klopfenstein, Ned B. , 2013

Principal Investigators: 
Forest Service Partners: 
US Forest Service, Pacific Northwest Research Station

External Partners: 
Principal Investigator or Subject Matter Expert for this Research Highlight* Amy Ross-Davis (RMRS collaborator), Jane Stewart (University of Georgia), and Ned B. Klopfenstein (RMRS)

USDA ARS, University of Georgia, Kookmin University (Seoul, South Korea), Utah State University