In 1973, a new disease of Dendrobium was found in Mie Prefecture. In the beginning, small tiny brown spots occurred on either side of the leaves. They shortly developed into round to oval or irregular large spots. The diseased leaves gradually discolored, but spots on them left green borders. Eventually these leaves defoliated. Many pycnidia of a species of the genus Selenophoma were formed on old spots.
The result of the artificial inoculation indicated that Dendrobium spp. were susceptible to this fungus, while Cattleya sp., Cymbidium sp., Miltonia sp. and Oncidium sp. did not develop any symptom of the disease. On the basis of differences in morphological characters and host range from the hitherto known species of the genus Selenophoma, the fungus was treated as a new species causing the leaf spot of Dendrobium.
Selenophoma dendrobii Abiko, sp. nov.
Foliicola; maculis amphigenus, primo brunneis, 0.5-1mm diam., dein griseo-brunneis vel cinereus, 5-10mm diam.; pycnidiis amphigenus immersis dein erumpentibus, brunneis vel atro-brunneis, globosis, 72-120μm diam., ostiolatis; conidiophoris simplicis, hyalinis; conidiis (pycnidiosporidiis) hyalinis, continuis, falcatis, 5-8×1-2μm.
Hab. on living leaves of Dendrobium Formidible (S. Takagi) Griggs, Tsu, Mie Pref., Nov. 1. 1973, by K. Abiko (Type). Type: Herb. Vegetable and Ornamental Crops Res. Sta. (=Herb. National Science Museum, F-226369)
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