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

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.

Developmental Characteristics and Auxin Response of Epiphytic Root in Dendrobium catenatum

“…During Dendrobium seedling growth and propagation, 0.1–2 mg⋅L –1 NAA is usually added to the medium during aseptic culture ( da Silva et al, 2015 ). Auxin-producing endophytes in the velamen roots are beneficial for the root colonization of epiphytic orchids ( Faria et al, 2013 ; Pavlova et al, 2017 ; Shah et al, 2018 , 2021 , 2022 ; Deepthi and Ray, 2019 ; Chand et al, 2020 ). To explore the effect of auxin on the root development in D. catenatum , we transferred JP966 seedlings with the removal of roots to the medium containing different concentrations of NAA (0, 2, 5, 10, and 20 mg L –1 ), the phenotype was observed and recorded after 90 days of cultivation ( Figure 7 ).…”