Effects of Lactarius deliciosus and Rhizopogon roseolus ectomycorrhyzal fungi on seeds and seedlings of Scots and stone pines inoculated with Fusarium oxysporum and Fusarium verticillioides

Two isolates of the edible ectomycorrhizal fungi (ECM), Lactarius deliciosus and Rhizopogon roseolus, were tested against Fusarium oxysporum and F. verticillioides, causal agents of damping-off on seeds and seedlings of Scots pine (Pinus sylvestris) and stone pine (Pinus pinea). The effects of ECM on Fusarium spp. in the rhizosphere of Scots and stone pines were evaluated by: (1) co-inoculating ECM and Fusarium when seeding (seed test) and (2) co-inoculating eight-week-old seedlings (seedling test). The seed tests showed significant reduction of Scots pine seed germination when treated with F. verticillioides, but this effect was absent when co-inoculated with R. roseolus. Higher germination rates were observed in stone pine when F. oxysporum was co-inoculated with L. deliciosus than the pathogen inoculation alone. In the seedling test, Scots and stone pines were not apparently affected by Fusarium spp. No obvious changes in plant growth-related variables were observed in either assay. Root colonization of Scots and stone pine seedlings by R. roseolus was 15.5% and 12% for the seed assay, as well as 21.6% and 11% for the seedling assay. Lactarius deliciosus mycorrhizal roots were found only in Scots pine seedlings (10%). Rhizopogon roseolus and L. deliciosus are two promising fungi for pine seedling protection against Fusarium damping-off at nurseries.