Abstract

Phaius tankervilleae (Banks) Blume is the most attractive and most horticulturally valuable native Phaiusspecies in Taiwan. Due to overharvesting in the wild, however, the plant is on the verge of extinction. Successful cultivation of P. tankervilleae has been achieved through in vitro seeding or tissue culture propagation, but plantlet survival rates are low upon transplantation. Previous studies demonstrated that inoculation with mycorrhizal fungi markedly improved plantlet survival rates, vegetative and reproductive growth in Orchidaceae plants. Four orchid mycorrhizal fungi (OMF), R01 (Rhizoctonia solani), R02 (Rhizoctonia sp., teleomorph = Ceratobasidium sp. AG-A), R15 (Rhizoctonia sp., teleomorph = Ceratobasidium sp. AG-Fb) and R19 (Rhizoctonia sp., teleomorph = Ceratobasidium sp. AG-G) were isolated from Taiwanese native orchid roots that were cultured for more than seven years in our laboratory. These fungi all proved to be non-pathogenic and were inoculated onto the root of P. tankervilleae. Inoculation with the appropriate OMF increased seedling survival rate 27 to 31% (R02; R15), plant height 6.3 cm (R15), leaf length 3.5 cm (R15), flower stalk length 10.2 cm (R19) and number of flowers per stalk (3.5) in ex vitro-grown P. tankervilleae. Inoculation with OMF (R19) promoted reproductive growth in P. tankervilleae, while OMF (R02) inoculation significantly increased photosynthetic rate and carbohydrate content. P. tankervilleae seedlings inoculated with the R15 isolate had a higher survival rate than with other treatments. Inoculations with Rhizoctonia spp. isolates R02, R15, or R19 also promoted reproductive growth in P. tankervilleae.

Key words: Pelotons, Phaius tankervilleae, reproductive growth, Rhizoctonia species, survival rate, vegetative growth.