Effects of Three Vesicular-Arbuscular Mycorrhizal Fungi on Sweetgum Seedlings from Nine Mother Trees
Soil in microplots was infested with three vesicular-arbuscular (VA) symbionts then sown with seed of half-sib progeny from nine sweetgum mother trees. The VA treatments were Glomus fasciculatus, Glomus spp. (a mixture containing both Glomus mosseae and Glomus etunicatus), or a VA mixture of several fungi from the genera Glomus and Gigaspora. Before the seed was sown, all plots had calcium standardized and received an application of commercial fertilizer. During the growing season, NH4NO3 was applied to all plots in equal portions. Mycorrhizal seedlings with G. fasciculatus were slightly but not significantly larger in both height and root-collar diameter than were seedlings with the Glomus spp. or the VA mixture. Seedlings from all VA treatments were approximately 32 cm tall with root-collar diameters of approximately 0.70 cm. Nonmycorrhizal seedlings averaged 4.5 cm in height and 0.19 cm in root-collar diameter. Progeny from four of the mother trees were consistently larger than those from the other five, but progeny from three of these five were consistently smaller regardless of the VA mycorrhizal treatment. From a given mother tree, no significant difference in progeny ranking was observed among treatments. Significant differences in percentage of roots infected and in intensity of infection within root segments were found among the three treatments, but these differences were not correlated with seedling growth. There were some differences in mineral analyses of tissue from seedlings among the different mycorrhizal treatments and the control but no consistent trends were observed in any of the parameters in the tests. Forest Sci. 27:327-335.
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