Mycorrhizal fungi associated with Kenyan terrestrial orchids and their role in orchid seed germination

Abstract

Terrestrial orchids are threatened with extinction due to loss of their habitat. This has created awareness towards their in situ and ex situ conservation. Orchids form mycorrhizal association and their seeds rely on this association for germination in nature. For the successful in vitro seed germination, inoculating with an appropriate mycorrhizal fungus has proved necessary. Kenyan terrestrial orchids were assessed for mycorrhizal fungi and the role the fungi play in seed germination. Isolation was carried out on 14 orchid species namely; Eulophia stenophylla, E. montis-elgonis, E. orthoplectra, E. horsfallii, E. petersii, E. streptopetala, Bonatea steudneri, Liparis bowkeri, Satyrium crassicaule, Disa stairsii, Habenaria petitiana, Satyrium corriophoroides, Cynorkis anacamptoides and Satyrium sacculatum. The species were collected from different localities- in Kenya and Fungal Isolating Medium (FIM) was used for the isolation of the mycorrhizal fungi," ." Out of the 24 fungal isolates obtained, eight were found to belong to the form-genus Rhizoctonia nc., the group which is known to form mycorrhizal association with orchids. Specific identification wets-not possible due to lack of conclusive identification keys for this group of fungi. A taxonomic description of the mycorrhizal fungal isolates is given. - Symbiotic germination tests were carried out on five orchid species namely; Bonatea steudneri, Liparis bowkeri, Eulophia horsfallii, Satyrium crassicaule and Cynorkis anacamptoides. Out of these, three species were stimulated to germinate symbiotically namely; L. bowkeri, S. crassicaule and C. anacamptoides. Satyrium crassicaule was stimulated to germinate by Rhizoctonia spp. Nos. 494/95/1010, 520/9511018, 515/9511017 and 536/9511 020. Cynorkis anacamptoides was stimulated to germinate by Rhizoctonia spp. Nos. 494/9511010 and 520/95/1018. Rhizoctonia sp. No. 494/9511010 was the most efficient in stimulating the germination of C. anacamptoides and S. crassicaule. Liparis bowkeri was stimulated to germinate by Rhizoctonia sp. No. 515/9511 0 17 only. Isolation and identification of orchid mycorrhizal fungi and symbiotic germination technique were a prerequisite for the propagation of endangered temperate terrestrial orchid species. The work presented here suggests that the symbiotic germination assay can also be applied on endangered Kenyan terrestrial orchids.