Endomycorrhizal infection of containerized yellow-poplar seedlings

Yellow-poplar, an important hardwood in the Southern Appalachians, can be infected with the endomycorrhizal fungi, Glomus masseae (Nicol. and Gerede.) Gerdemann and Trappe and Glomus fasuculatus (Thaxter) Gerdemann and Trappe. Objectives were to determine (1) the effects of various mycorrhizal inocula on seedling growth, (2) the developmental patterns of seedling root infection and corresponding seedling growth, (3) a correlation between fungal structures and seedling growth rates (4) the technology of seedling propagation in Spencer-Lemaire rootrainers. Sterilized growth medium in rootrainers was amended with inocula of Glomus mosseae, Glomus fasciculatus, Glomus masseae plus Glomus fasciculatus soil from a natural yellow-poplar stand, or no inocula at all. Two to three week old yellow-poplar seedlings were planted in the respective media in rootrainers and grown in greenhouse culture. The plants were harvested at 3, 5, 7, 9, 12 and 16 weeks after planting and measured for root length, shoot length, stem diameter at the root collar and oven-dry weight. Total length of the plant and root to shoot ratio was also analyzed. The roots were preserved and later stained to quantify the amount of free hyphae, arbuscules, vesicles and hyphal coiling. All seedling roots from mycorrhizal treatments had fungal structures developing. No fungal structures were found in the uninoculated controls. Seedlings exposed to the uninoculated medium had the lowest growth rate for all growth variables except root length. The seedlings exposed to the natural inoculum were intermediate between the control seedlings and those exposed to the mixture of Glomus mosseae and Glomus fasciculatus. The seedlings exposed to the single inocula of Glomus mosseae and Glomus fasciculatus were the largest. There appeared to be some interaction between the endophytes when mixed in treatments, thereby leading to a loss of efficiency in the mycorrhizal relationship. Each acceleration growth corresponded to an increase of all fungal structures except vesicles. Vesicles were most abundant in the natural inoculum seedlings. There were no statistically significant correlations between any fungal structure and any growth variable.