Studies of Mycorrhizal Fungi of Chinese Orchids and Their Role in Orchid Conservation in China—A Review

Abstract

China has over 1,200 species of native orchids in nearly 173 genera. About one fourth of native species are of horticultural merit. Some species are of Chinese medicinal value. In fact, the demand on orchid species with high Chinese medicinal values such as Gastrodia elata, Dendrobium offcinale, along with demands on species of cultural importance, such as those in the genus of Cymbidium, is a major factor causing wild populations to diminish and in some cases, drive wild populations to the brink of extinction. These market demands have also driven studies on the role of mycorrhizal fungi in orchid seed germination, seedling and adult growth, and reproduction. Most of these mycorrhizal studies of Chinese orchids, however, are published in Chinese, some in medical journals, and thus overlooked by the mainstream orchid mycorrhizal publications. Yet some of these studies contained interesting discoveries on the nature of the mycorrhizal relationships between orchids and fungi. We present a review of some of these neglected publications. The most important discovery comes from the mycorrhizal studies on G. elata, in which the researchers concluded that those fungi species required to stimulate seed germination are different from those that facilitate the growth of G. elata beyond seedling stages. In addition, presence of the mycorrhizal fungi associated with vegetative growth of post-seedling G. elata hindered the germination of seeds. These phenomena were unreported prior to these studies. Furthermore, orchid mycorrhizal studies in China differ from the mainstream orchid studies in that many epiphytic species (in the genus of Dendrobium, as medicinal herbs) were investigated as well as terrestrial orchids (mostly in the genus Cymbidium, as traditional horticultural species). The different responses between epiphytic and terrestrial orchid seeds to fungi derived from roots suggest that epiphytic orchids may have a more general mycorrhizal relationship with fungi than do terrestrial orchid species during the seed Bot. Rev. (2010) 76:241-262 germination stage. To date, orchid mycorrhizal research in China has had a strongly commercial purpose. We suggest that this continuing research on orchid mycorrhizal relationships are a solid foundation for further research that includes more rare and endangered taxa, and more in-situ studies to assist conservation and restoration of the endangered orchids. Knowledge on the identities and roles of mycorrhizal fungi of orchids holds one of the keys to successful restoration and sustainable use of Chinese orchids.

Analysis of fungal diversity in Orchis tridentata Scopoli

“…For instance, the presence of appropriate fungal species is needed for long-term success of traslocation efforts [20]. Transplantation into the nature of orchid seedlings associated with their mycorrhizal partners and in situ land inoculation with fungal symbionts could be of primary importance for conservation efforts [22,50].…”

Conservation of the Native Orchids Through Seedling Culture and Reintroduction—A Singapore Experience

“…For example, pollinators may be attracted to come back to pollinate the flowers. Orchid seeds that are formed naturally after flowers are pollinated may be blown to the proper environment where appropriate mycorrhizal fungi are present (Liu et al, 2010b). And we hope that one day we will be able to see natural populations of native species sprouting up all over the island!…”

“…Other pollinator attracting mechanisms include deceitful floral mimicry and production of insect pheromones (van der Pijl & Dodson, 1966;Pemberton, 2010;Vereecken et al, 2010). All orchids are myco-heterotrophic at some point in their life cycle (Liu et al, 2010b), i.e., they rely on fungi for their nutrients (Hartley & Smith, 1983). This relationship between orchid roots and a variety of fungi is known as orchid mycorrhiza.…”

Gastrolatathioneine, an unusual ergothioneine derivative from an aqueous extract of “tian ma”: A natural product co-produced by plant and symbiotic fungus

“…Compound 1 is the first ergothioneine derivative isolated and structurally characterized from a plant extract since all the previously reported ergothioneine-derived natural products are from fungi and animal [33,35,36,41]. Because G. elata is a holomycotrophic plant living on a symbiotic mycorrhizal fungus Armillaria mellea [42], the absence of the biosynthesis genes of ergothioneine in the higher eukaryotes indicates that 1 is co-produced by the plant and symbiotic fungus, e.g. the later synthesizes and provides the precursor ergothioneine for the former to make 1.…”