ABSTRACT
Orchids depend on mycorrhizal fungi for nutrition, especially during early developmental stages. Some orchid species are specific in their interactions, while others have a variety of fungal associations. Orchid mycorrhiza belongs to at least five major taxonomic groups such as Glomeromycota, Basidiomy-cota, Ascomycota, Agaricomycetes and Sordariomycetes fungi. The terrestrial orchids are more dependent on orchid mycorrhizal fungi (OMF) interactions for the nutritional requirement in comparison to epiphytic orchids because their protocorms become photosynthetic at early life stages. Various omics approaches are employed to understand the complexity of OMF interaction, 296which indicate that fungus augments orchid development through regulation of various transcription factors (DMI, NSP, WRKY, GRAS, SWEET, CCaMK, ENODL, TPP etc.), involved in plant growth and development. In addition to this, tissue culture studies involving symbiotic seed germination and further development in the presence of the specific mycorrhizal partner, promotes seed germination and robustness of the seedlings. The studies on orchid mycorrhizal associations provide a conceptual framework to understand the mechanisms of selection of fungal partner, establishment of the symbiotic association, nutritional aspects, and ecological adaptations. The present chapter provides an outline on possible physiological, molecular and ecological approaches involved in the study of OMF interactions.
