Mycorrhizal morphotyping and molecular characterization of Chondrogaster angustisporus Giachini, Castellano, Trappe & Oliveira, an ectomycorrhizal fungus from Eucalyptus

Chondrogaster angustisporus is a hypogeous ectomycorrhizal fungus described from fruiting bodies collected under Eucalyptus spp. in Brazil, Uruguay, and Australia. Due to its efficiency in promoting plant growth, we decided to characterize this fungus through mycorrhizal morphotyping and internal transcribed spacer (ITS) (rRNA) sequencing. DNA extracted from mycelium was amplified and sequenced using specific primers. Mycorrhizas were obtained aseptically and analyzed in terms of macroscopic and microscopic characteristics. When compared with other fungal DNA sequences available in the NBCI GenBank, the C. angustisporus sequence presented the highest similarity to an uncultured ectomycorrhizal fungus from the Seychelles. It also shows significant similarities to Gomphus, Ramaria, and Hysterangium species supporting the classification of Chondrogaster in the subclass Phallomycetidae in the gomphoid-phalloid group. The mycorrhizas were characterized by a narrow mantle with a single tissue layer densely arranged and organized as a net synenchyma with elongated hyphae. Interhyphal spaces were seen only in the external region where hyphae were more loosely organized. Bottle-shaped cystidia with bent necks were observed on the surface of the mantle. Emanating hyphae were larger than those in the mantle and presented a granular content. At regular intervals the hyphae were divided by septa with clamp connections. The Hartig net was of the common type, with typical palmetti and single hyphal rows and limited to the epidermal layer. The mycorrhizal description and the ITS sequence obtained are useful tools to identify this ectomycorrhizal fungus in culture and in association with Eucalyptus roots.