Applications of endophytic-fungal-isolates from velamen root of wild orchids in floriculture

Azhanthanilkunnathil S Deepthi,Joseph G Ray

doi:10.21472/bjbs.061409

Abstract

The velamen roots are quite extensively growing and profusely branched organ of adaptation in epiphytic orchids. The endophytic-fungi in such roots are believed to have growth-promoting influence, especially on the roots itself. However, an application of the same in the cultivation of the ornamental orchids is not yet sufficiently tried. The present report deals with the growth promoting effects of endophytic fungi of the velamen roots of a wild epiphytic orchid Acampe praemorsa on an ornamental orchid, Dendrobium sp. The five endophytic fungal species, Trichoderma asperellum, Trichoderma harzianum, Trichoderma atroviride, Endomelanconiopsis endophytica and Diaporthe eucalyptorum isolated from the velamen roots of the epiphytic orchid, A. praemorsa were found to be potent producers of the hormone indole-3-acetic-acid (IAA). The endophytic fungi were identified by morphological and molecular methods. The nucleotide sequences of the identified strains were deposited in the GenBank. The growth-promoting influence of them was tested on an ornamental orchid Dendrobium sp. Experimental assessment of nutrient uptake, chlorophyll content, and biomass of the leaves of the treated plants after 45 days of inoculation confirmed the growth promoting effects. The amount of nitrogen, phosphorus and potassium in the treated plants showed a significant increase from the control. The fungus E. endophytica showed a significant increase in the chlorophyll content in the leaves of treated plants; T. asperellum and D. eucalyptorum showed a significant increase in the fresh-weight of treated plants, whereas T. asperellum and E. endophytica significantly increased the dry weight of leaves in treated plants. Overall, the experiment proved that the endophytic fungal isolates from the wild orchid A. praemorsa synthesize bioactive compounds including IAA that can promote growth in ornamental orchids such as Dendrobium sp. Thus the endophytic fungal isolates from wild orchids are proved significant in orchid floriculture.

Highlights

The symbiotic fungal endophytes are beneficial to its host (Wang et al, 2015).The fungal endophytes are potent producers of phytohormones and other bioactive compounds (Khan et al, 2015) in many plants
The segments were placed in Petri dishes containing approximately 15-20 ml of potato dextrose agar medium (PDA) of pH 5.8, malt extract agar medium (MEA) of pH 5.8 and sabouraud dextrose agar medium (SDA) of pH 5.6. 100 μg ml-1 streptomycin was added to each medium to prevent bacterial growth
It was found that five endophytic fungal isolates from the velamen root of a wild Orchid A. praemorsa are capable of producing phytohormone IAA

Summary

Introduction

The symbiotic fungal endophytes are beneficial to its host (Wang et al, 2015).The fungal endophytes are potent producers of phytohormones and other bioactive compounds (Khan et al, 2015) in many plants. Endophyticfungi are believed to be significant in the natural existence of many species of plants (Kedar et al, 2014). Exploration of such fungi, quite common in wild species can have potential application in agriculture, horticulture, biotechnology and the natural products industry (Guo et al, 2008; Nisa et al, 2015). The plant Dendrobium, an epiphytic orchid is the second largest genus of the Orchid family with more than 1000 species (Shah et al, 2019). It is one of the most popular ornamental orchid valuable as cut flowers in South Asia (Hágsater and Dumont, 1996). Applications of endophytic fungi from wild Orchids, especially that from the velamen roots are not yet tried in this plant

Methods

Results

Discussion

Conclusion