The ectomycorrhizal symbiosis is known to improve the growth of forest trees in several ways: mineral nutrition, protection against root pathogens, growth regulators, water absorption. This latter aspect, rather neglected until now, has to be investigated. Controlled mycorrhization is beginning to develop in forestry practice and it is important to know to what extent the selection of the fungal strains to be inoculated in the nurseries might improve the resistance of planting stocks to water stress, a major factor of mortality in young plantations.
The project provided new insights into the role of ectomycorrhizal symbioses in the resistance of young forest tress to drought stress. The work was carried out with 3 tree species: Norway spruce (Picea abies); Douglas fir (Pseudotsuga menziesii); eucalypt (Eucalyptus globulus) and a number of isolates of ectomycorrhizal fungi belonging to 6 species: Pisolithus tinctorious; Laccaria laccata; Thelephora terrestris; Cenococcum geophilum; Paxillus involutus; and an unidentified fungus forming white mycorrhizas with mycelial stands. It was found that ectomycorrhizal fungi differ in the contribution to water management by young forest trees and some of the mechanisms involved have been identified. A laboratory test was developed for assessing the protective effect of ectomycorrhizal fungi under drought stress and comparative experimental plantations with different fungal associates have been created. The first results demontrate that some fungal strains, selected with the appropriate hosts, improve survival and early growth of the plantations.
The work will be done with Norway spruce, Douglas fir and Eucalyptus globulus, using four complementary approaches.
Comparison of water status (total and osmotic potential) and gas exchange regulation of non-mycorrhizal plants and plants mycorrhizal with different fungi, in water stress or non-limiting water conditions.
On the same type of plant material, using tritiated water and fluorescent apoplasmic dyes at different soil water potential, comparison of water pathways into non-mycorrhizal and mycorrhizal roots. Fungi forming mycorrhizas with and without rhizomorphs or mycelial strands will be compared.
Studying water relations of ectomycorrhizal fungi in pure mycelial culture; developing a laboratory test for screening fungal species and strains according to their ability to survive and grow at low water potential and protect the root against drying.
Measuring water status and photosynthesis in the field, in experimental forest plantations with plots where plants are associated with different mycorrhizal fungi.
Funding SchemeCSC - Cost-sharing contracts