Two species of Vesicular-Arbuscular Mycorrhizal (VAM) fungi, Glonnis intraradices and Glomus mosseae, were evaluated in a 2 year field experiment and a greenhouse experiment, for their effects on growth and nutrient uptake of Ottawa 3 apple rootstock in soil infested with the root-lesion nematode, Pratylenchus penetrans. Plants were inoculated with one of the two species of VAM fungi prior to planting into fumigated and non-fumigated field plots. Non-fumigated plots were naturally infested with the nematode and fumigated plots were re-infested with the nematode at the time of transplanting. The abundance of vesicles and arbuscules was greater in roots of plants inoculated with VAM fungi than in roots of non-inoculated plants, even in non-fumigated plots where roots were colonized by native VAM fungi. Inoculation with VAM fungi increased plant growth and leaf concentrations of P, Cu, Mg, and Zn in fumigated plots but not in non-fumigated plots, indicating that colonization by the native VAM fungi in non-fumigated plots may have been sufficient for adequate nutrient acquisition. Inoculation with VAM fungi reduced populations of P. penetrans in roots and soil from the root zone. The effect of VAM fungi on nematode populations was most pronounced in fumigated soil, indicating that nematode suppression may contribute to the improved plant growth and nutrient uptake observed for VAM-inoculated plants in fumigated soil. In greenhouse studies, colonization of apple roots by VAM fungi was reduced by P. penetrans.
