title: Characterization and colonization of endomycorrhizal Rhizoctonia fungi in the medicinal herb Anoectochilus formosanus (Orchidaceae).
abstract: The medicinal effects and techniques for cultivating Anoectochilus formosanus are well-documented, but little is known about the mycorrhizal fungi associated with A. formosanus. Rhizoctonia (Thanatephorus) anastomosis group 6 (AG-6) was the most common species isolated from fungal pelotons in native A. formosanus and represented 67% of the sample. Rhizoctonia (Ceratobasidium) AG-G, P, and R were also isolated and represent the first occurrence in the Orchidaceae. Isolates of AG-6, AG-R, and AG-P in clade I increased seed germination 44-91% and promoted protocorm growth from phases III to VI compared to asymbiotic treatments and isolates of AG-G in clade II and Tulasnella species in clade III. All isolates in clades I to III formed fungal pelotons in tissue-cultured seedlings of A. formosanus, which exhibited significantly greater growth than nonmycorrhizal seedlings. An analysis of the relative effect of treatment ([Formula: see text]) showed that the low level of colonization ([Formula: see text]) by isolates in clade I resulted in a significant increase in seedling growth compared to isolates in clades II (0.63-0.82) and III (0.63-0.75). There was also a negative correlation (r = -0.8801) with fresh plant weight and fungal colonization. Our results suggest that isolates in clade I may represent an important group associated with native populations of A. formosanus and can vary in their ability to establish a symbiotic association with A. formosanus. The results presented here are potentially useful for advancing research on the medicinal properties, production, and conservation of A. formosanus in diverse ecosystems.
authors.affiliation: Department of Plant Pathology, National Chung Hsing University, No. 250, Kuo-Kuang Road, Taichung, Taiwan.
authors.forename: Jr-Hau
authors.initials: JH
authors.lastname: Jiang
authors.forename: Yung-I
authors.initials: YI
authors.lastname: Lee
authors.forename: Marc A
authors.initials: MA
authors.lastname: Cubeta
authors.forename: Lung-Chung
authors.initials: LC
authors.lastname: Chen
mesh_terms: D018533:Biomass; D038821:Mycorrhizae / Q000145:classification* / Q000302:isolation & purification* / Q000502:physiology; D029595:Orchidaceae / Q000382:microbiology*; D063245:Plant Development; D010946:Plants, Medicinal / Q000382:microbiology*; D012232:Rhizoctonia / Q000145:classification* / Q000302:isolation & purification* / Q000502:physiology; D036226:Seedlings / Q000382:microbiology; D012639:Seeds / Q000382:microbiology; D013559:Symbiosis