Figure 1: Mycorrhizal fungi promote the growth of tissue culture seedlings of Dendrobium officinale.

Abstract

Dendrobium officinale is a medicinal herbal plant with important health care value and high demand. Due to its slow growth and scarcity in nature, its yield depends on intensified cultivation while biotic and abiotic stresses were important factors that causes production loss. Orchidaceae can form association with rhizoctonias collectively, and studies have found that some orchids showed a high level of strain-species specificity to orchid mycorrhizal fungi (OMF), yet the specificity of OMF on D. officinale needs to explored. In this study, the effects on D. officinale of four OMF isolated from Cymbidium were tested. The obviously higher mass yield of the treated plants in medium and pots indicated the growth promotion effect of the fungi. Furthermore, an abiotic stress test indicated stronger drought tolerance among the treated plants. For the biotic stress test, two root rot pathogens, Fusarium solani and Fusarium graminearum , were isolated and identified from root rot of D. officinale. In an in vitro inhibition test, the four OMF could resist the growth of these pathogens. In vivo studies showed that these four OMF could improve the survival rate and fresh weight and decrease the root rot rate of pathogen-inoculated seedlings. The four OMF namely; Hyphomycete sp., Umbelopsis sp., Ceratorhiza sp. and Ceratorhiza sp. are compatible strains for improving the growth rate of D. officinale by increasing its environmental stress tolerance, providing an effective way to supply resources through artificial reproduction.