EFFECTS OF THE ROOT-LESION NEMATODE PRATYLENCHUS-VULNUS AND THE VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS-MOSSEAE ON THE GROWTH OF 3 PLUM ROOTSTOCKS

The effects of Pratylenchus vulnus and the endomycorrhizal fungus Glom us mosseae on growth of Myrobalan 605, Marianna 2624 and San Julian 65 5-2 plum rootstocks were measured under shadehouse conditions in the f ield for two growing seasons (1990-91). Shoot dry weights were higher in the majority of the vesicular-arbuscular mycorrhizal (VAM) alone in oculated plants after both growing seasons. Root weights of mycorrhiza l Myrobalan and Marianna were higher than root weights of the same roo tstocks lacking mycorrhizae, inoculated with P. vulnus, and VAM in com bination with the nematode. Mycorrhizal Marianna inoculated with the n ematode showed a considerably higher final nematode population in rela tion to non-inoculated VAM treatments. No correlation was found in the number of nematodes per gram of root between mycorrhizal and non-myco rrhizal treatments. P. vulnus adversely affected the mycorrhizal colon ization in Marianna, but not in Myrobalan and San Julian. Marianna app ears to be more mycorrhizal dependent than the two other rootstocks.