Damage due to Armillaria root rot is serious in all EEC countries, particularly in plantation monocultures of conifers, fruit trees, ligneous ornamental and floral cultures. It is also found in more natural ecosystems, even deciduous forest, especially if trees have been stressed. The last decade of research has shown that in Europe there are six species of Armillaria differing in their pathogenicity, ecological and host specialisation. Two EEC research projects have for the last two years expanded such knowledge and indicated in which directions continued research is necessary. The ultimate aim of reducing loss due to Armillaria root either by ecological, biological, genetical, or in some cases chemical control depends on a thorough understanding of this fungus.
In this project 6 contractors and 6 subcontractors propose three main topics of research: the differences between and identification of species; the pathogenicity of different species; control methods.
Characteristics of the different Armillaria species in Europe.
Differentiation of a species in the laboratory: studies will be made with a scanning electron microscope of undifferentiated mycelium. Fruiting and morphology in culture will be further investigated. An immunological test based on monoclonal antibodies will be developed.
Ecological role in the forests of southern Europe: surveys in Italy about the distribution and role of Armillaria species will be extended. The first studies of this kind will be undertaken in Greece.
Equilibrium between the different Armillaria species in nature: the equilibrium established between different Armillaria species found in proximity will be examined in different ecosystems, taking into account the effect of human intervention and other factors modulating competition among species.
Pathogenicity of the different Armillaria species in Europe.
Determinants of pathogenicity (enzymes and toxins): those enzymes (cellulases, xylanases, suberinases, pectinases and proteases) involved in the cell wall degradation of a ligneous host will be studied. Toxins (low molecular weight molecules targeting host cell protoplasm) will be extracted from pure fungal culture or dual cultures where the fungus is confronted with the host. Biotests with toxins will be performed on isolated cells and tissue cultures.
The influence of stress on pathogenicity: modifications in host susceptibility to different Armillaria species in relation to varying degrees of water stress will be studied.
Intraspecific variation in pathogenicity: comparisons will be made of isolates of A ostoyae taken from sites of natural infection where differences in pathogenicity have been observed. A miniaturised inoculation method will be developed so that the pathogenicity of such isolates (to Pinus Pinaster) can be reliably but rapidly tested.
Control methods for the different Armillaria species in Europe.
Chemical control: systemic fungicides will be screened.
Biological control: lignicolous fungi antagonistic to Armillaria species will be selected. Inoculated on old stumps they would reduce the inoculum potential of Armillaria and protect young trees.
Genetical control: conifers (especially Pinus species), deciduous trees such as Quercus, Populus and Eucalyptus, fruit trees and ligneous floral cultures will be artificially inoculated and screened for resistance.
Funding SchemeCSC - Cost-sharing contracts
OX1 3RB Oxford