Simplified Ex Vitro Symbiotic Seed Germination of Orchids

Abstract

Orchid seed germination is a propagation method used in the selection of hybrids and conservation programs. Even though asymbiotic germination is the most widely used approach, symbiotic germination is gaining popularity. Ex vitro symbiotic germination is a simple seed germination method that does not require axenic condition from seed sowing step onwards. The present study modified the previously reported ex vitro symbiotic germination method by optimizing components of germination substrate and using plastic food containers with lids vented with air-permeable film to reduce the problem of mite and fungal contamination. We also demonstrated successful seed germination of four orchid species [i.e., Spathoglottis affinis de Vriese, Paphiopedilum hirsutissimum (Lindl. ex Hook.) Stein, Paphiopedilum gratrixianum Rolfe and Dendrobium parishii Rchb.f.] using the established method and effective isolates of an orchid mycorrhizal fungus, Tulasnella deliquescens (Juel) Juel. Although the established method resulted in less germination percentages and percentages of Stage 5 protocorms compared to asymbiotic medium (i.e., half strength of Murashige and Skoog medium) in three studied orchids, it supported more rapid growth of Paphiopedilum protocorms/seedlings. Other potentials and limitations of the established method are discussed in this article.