Two experiments with Malus domestica sp. were planted in 1997 at the Laval Univ. experimental farm located south of the St. Lawrence river near Quebec City. These experiments examined the association of the mycorrhizal fungus Glomus intraradices with Malus domestica sp. The first experiment compared the vegetative growth of `McIntosh' apple trees on M.106 rootstock in presence or absence of a commercial inoculum of G. intraradices (Premier Tech, Riviere-du-Loup, Quebec) under three levels of phosphorus fertilization (P) to the soil (0%, 50%, and 100% of the usual recommandation for this crop). After two seasons, all the treatments had better growth than the control (0% P without G. intraradices). The best treatment was achieved with 100% of the P associated with mycorrhizal inoculation. The second experiment compared the vegetative growth of three apple rootstocks Bud.9, M.26, and M.106, inoculated with G. intraradices under the same three P levels as the preceding experiment. Uninoculated rootstocks receiving the usual phosphorus fertilization served as control. Two roostocks, M.26 and M.106, increased growth with G. intraradices, while the third one, Bud.9, did not respond to the presence of mycorrhizal fungus.