Formation of endomycorrhizas by an achlorophyllous orchid, Erythrorchis ochobiensis, and Auricularia polytricha

Abstract

To test the mycorrhizal function of heterobasidiomycetous fungi on achlorophyllous orchids and to examine the symbiotic fungal range of a myco-heterotrophic orchid, Erythrorchis ochobiensis, synthetic cultures of the orchid seed were carried out with Auricularia polytricha isolates from Japan and Mexico. After three and a half mo of incubation, 57.0-70.7% of seeds germinated but none of them showed further growth. When cultured on peat moss at 25~ the germination rate was 8.7% in the presence of Mexican isolate and 18.0% in the presence of Japanese isolate. Some germinated seeds developed into protocorms, and several seeds incubated with the Mexican isolate developed into plantlets after 5 too. Pelotons were observed in the cells of protocorms and roots. The results indicated that some heterobasidiomycetous fungi could form endomycorrhizas with a myco-heterotrophic orchid. The results also showed that the symbiont of E. ochobiensis extends, at least experimentally, to Heterobasidiomycetes. The variances of germination rate and seedling growth were suggested to be affected by the difference of isolates and culture conditions.

Basidiomycota: Homobasidiomycetes

“…Orchid associates are found in the euagarics clade (Armillaria, Ceratobasidium, and Lentinula), cantharelloid clade (Tulasnella), polypore clade (Ganoderma, Loweporus, Microporus), and hymenochaetoid clade (Erythromyces and Phellinus) (Currah and Zelmer 1992;Umata 1995Umata , 1998, as well as in the Auriculariales (Umata 1997). However, it is not known whether Lentinula and the polypores and hymenochaetoid fungi listed form fully functional orchid mycorrhizae in nature, or only promote orchid seed germination (Umata 1995(Umata , 1998.…”

Evidence for novel and specialized mycorrhizal parasitism: the orchid Gastrodia confusa gains carbon from saprotrophic Mycena

“…Species of the genus Gastrodia and its related genus Didymoplexis are suspected to associate with several decomposer fungi such as Armillaria, Marasmius and Fomes (Burgeff 1932;Campbell 1962Campbell , 1964. The world's largest nonphotosynthetic plant, Erythrorchis ochobiensis, is reported to form mycorrhizas with a wide range of wood-rotting fungi (Hamada & Nakamura 1963;Umata 1995Umata , 1997Umata , 1998a. Mycorrhizal parasitism is also supported by recent work in the non-photosynthetic orchid Epipogium roseum with a litter-decomposing Coprinaceae spp.…”

A new biological function of Shiitake mushroom, Lentinula edodes, in a myco-heterotrophic orchid, Erythrorchis ochobiensis

“…The temperature of 30~ is suggested to be very effective for the seed germination of E. ochobiensis under the symbiotic and non-symbiotic cultural conditions from the present results and Nakamura's (1962). Seeds cultured symbiotically with A. polytricha showed a little difference in germination rates: 57.4~ in a Mexico isolate and 57.0~ in a JPN slate at 25~ compared to 57.9~ in Mexico and 70.7~ in JPN at 30~ (Umata, 1997). In the case of L. edodes cultured on Srice-M, the germination rate was altered drastically by the cultural temperature and by the isolate.…”

“…Sacc. (Auriculariales) was also found to form normal endomycorrhiza (Umata, 1997). However, the symbiotic abilities with this orchid of fungi of the Agaricales remain obscure.…”

“…or Lithocarpus edulis (Makino) Nakai. The pH of the medium was 5.7 after autoclaving for 60 min at 121 ~ Methods of synthetic cultures followed Umata (1997). Each isolate was inoculated into about 70 g of the medium in 200-ml flask and incubated at 25~ for 3 wk.…”