Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Plant Pathology and Microbiology


The roots of Acer nigrum Michx.f., Fraxinus pennsylvanica Marsh., Platanus occidentalis L., Juglans nigra L. and Populus deltoides Bart., growing in lawn and woods, were examined for endomycorrhizae. Some of these species were part of one greenhouse and 2 microplot studies in which screening of endomycorrhizal fungi and fungal infestations of fumigated and nonfumigated soils were examined for growth enhancement potential. In a 1979 microplot study, F. americana L., J. nigra and P. x euramericana (Dode) Guinier 'Eugenii' were grown in fumigated or nonfumigated Nicollet-Webster loam to which the mycorrhizal fungi, Glomus etunicatus Becker and Gerdemann, Glomus fasciculatus Isolate 1 Gerdemann and Trappe, G. fasciculatus Isolate 2 or pot culture filtrate was added. No significant difference in tree growth was noted among the fungal infestants. White ash and black walnut were significantly smaller when only pot culture filtrate was added to the fumigated soil. In 1980, a microplot study was performed in which F. americana, F. pennsylvanica and P. occidentalis were planted in a less fertile sandy loam soil. Two mycorrhizal fungi (G. fasciculatus Isolate 1 and G. etunicatus) and pot culture filtrate were added to fumigated and nonfumigated soil. Fungal infestations took place in a greenhouse several weeks before outplanting (preplant) and at the time of outplanting (post-plant) seedlings into microplots. In all instances, fumigated soil infestations with either fungus resulted in significantly larger trees. In general, trees grown in soil infested with G. fasciculatus exhibited greater growth than G. etunicatus and fungal infestations of nonfumigated soil resulted in larger trees than when soil was not infested with mycorrhizal fungi. In 1981, a greenhouse study was performed in which one mycorrhizal fungus (G. etunicatus), 2 tree species (F. americana and P. occidentalis), 2 infestation times and 2 soil types (Nicollet-Webster loam and unknown sandy subsoil loam) from previous microplot studies were used. In both soil types and with both tree species, fungal infestations of fumigated soil resulted in significantly larger trees. Growth results of infestation time treatments were influenced by soil type with preplant infestations showing more growth stimulation in Nicollet-Webster loam while post-plant infestations were more effective in sandy loam. In general, fungal infestations of nonfumigated soil stimulated greater tree growth than when no fungal infestations were made.



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Jon Eldon Warnke



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218 pages