Two members of the Glomeromycota form distinct ectendomycorrhizas with Alzatea verticillata, a prominent tree in the mountain rain forest of southern Ecuador

Mycorrhizas formed by members of the Glomeromycota with roots of Alzatea verticillata (Alzateaceae, Malpighiales), a characteristic tree of the neotropical mountain rain forest in southern Ecuador, were investigated using light microscopy. Two morphotypes are described. One morphotype forms very fine, fan-shaped branches in the intercellular space of the inner cortical layer. The fungus most probably belongs to the so-called fine endophytes. A second morphotype was distinguished by its larger hyphae and intercellular, ctenoid branches. In both morphotypes, arbuscules were formed, but vesicles and intraradical spores were lacking. The results show, for the first time, arbuscular mycorrhizas with abundant intercellular, finger-like branches resembling appressoria and reminiscent of the Hartig net structure in ectomycorrhizas. The Hartig net is known as a place for nutrient exchange and a similar function is presumed here. Consequently, the described morphotypes should be classified as ectendomycorrhizas. The presented results are also a contribution for distinguishing members of Glomeromycota by their vegetative structures.