Mycorrhizal Association and the Fungal Partner of Dendrobium Chrysotoxum and Dendrobium wardianum (Orchidaceae)

Development of mycorrhizal association and the exact fungal partner in the epiphytic Orchid species, viz., Dendrobium chrysotoxum and D. Wardianum, were investigated in the present study. Fungal entry was occurred by penetrating the root velamen layer and was characterised by the presence of an appresorial structure. The tolypophagy type of mycorrhizal infection with hyphae coiled into pelotons was restricted to the root cortical layer only. The size of the pelotons varied from 117.2±7.19×58.8±5.31 μm in D. chrysotoxum to 94.2±5.43×35.6±5.45 μm in D. wardianum. The mycorrhizal fungi were isolated from fresh, healthy roots of mother plants by adapting the modifed Masuhara and Katsuya's method. The hyphae were hyaline, smooth, binucleate and approximately 2.5±0.29 μm wide. Based on the morphological character, the fungi identifed as Epulorhiza repens in D. chrysotoxum and Ceratorrhiza ramicola and C. cerealis in D. wardianum.