Mycorrhizal symbionts associated with hybrid poplars from Iowa, USA

Seven clones of hybrid poplar, with parents from among four sections of the genus Populus, were potted in five Iowan soils. After a year they were sampled for mycorrhizae and endogonaceous spores. Eight species of Endogonaceae were recorded, seven known to form endomycorrhizae. Two ectomycorrhizal fungi, Ccnococcum geophilum and an unidentified species were noted. One poplar clone had fewer replicates in which Glomus fasciculatum spores were found, but otherwise there were no differences among the poplars in presence of spores. A soil from a P. grandidentata woodland had fewer pots with G. mosseae spores, while an agricultural soil had more occurrences of Gigaspora gigantea than other soils. No other significant differences among spores were noted for soils. Vesicles of endomycorrhizae occurred in all clones, but one was colonized more sparsely than the others. Two clones had ecto‐ and ectendo‐mycorrhizae, two types of the former being recorded. One of these clones had significantly more C. geophilum colonization than the other. There were indications of differences in mycotrophy among the sections of the genus Populus.