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On Earth,∼ 90% of angiosperm plants can form a mycorrhizal symbiosis with more than 50,000 fungal species belonging to Ascomycota, Basidiomycota, Glomeromycotina Mucoromycotina (Bruns et al., 2018; Tedersoo et al., 2020). The most ubiquitous mycorrhizal type are arbuscular mycorrhizae (AM, 72%), orchid mycorrhizae (ORM, 10%), ectomycorrhizae (ECM, 2%), and ericoid mycorrhizal (ERM, 1.4%)(Genre et al., 2020). Similar to ancient AM, the orchid mycorrhiza also partakes in endosymbioses with specific intracellular structures, but orchid plants have lost the ability to form arbuscular mycorrhizal symbiosis and represent clear symbiosis switches that have occurred during plant evolution (Radhakrishnan et al., 2020). Orchid mycorrhizal fungi transfer carbohydrates to their hosts, especially during the early germination and seedling stages, whereas other types of mycorrhizal fungi (eg, AM) primarily transport inorganic matter to host plants (Cameron et al., 2006; Parniske, 2008).

Because of their highly ornamental and medicinal value, orchid plants around the world are facing serious extinction so there is an urgent need to conserve them. The Dendrobium genus is one of the largest genera in the orchid family, and many species, such as Dendrobium officinale, are traditionally used in Chinese medicine. Orchid seeds generally lack endosperm and rely on mycorrhizal fungi to provide essential nutrients for germination, protocorm growth, and even adult plant development (Rasmussen et al., 2015). Most studies indicate that symbiotic germination is an effective technique for orchid conservation and ecological restoration in natural habitats …