VIEW ARTICLE

Protection of Douglas-Fir Seedlings Against Fusarium Root Rot by a Mycorrhizal Fungus in the Absence of Mycorrhiza Formation. R. W. Stack, Graduate Student, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; W. A. Sinclair, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, New York 14850. Phytopathology 65:468-472. Accepted for publication 7 November 1974. DOI: 10.1094/Phyto-65-468.

Douglas-fir seedlings inoculated in a controlled environment chamber with Fusarium oxysporum from a forest nursery developed root rot, had a high mortality rate, and grew poorly. When basidiospores of the mycorrhizal fungus Laccaria laccata were placed between seedling roots and inoculum of F. oxysporum in a mixture of soil, sand and perlite or vermiculite, less mortality and root rot occurred than in treatments receiving only F. oxysporum inoculum or F. oxysporum inoculum placed between roots and L. laccata spores. Mycelium of L. laccata prevented detrimental effects of F. oxysporum when placed in the soil mixture near seedling roots 1-3 weeks before introduction of F. oxysporum. Formation of mycorrhizae was not a prerequisite for the protective influence of the mycorrhizal fungus.