Functional characterization of a plant growth-promoting endophytic fungus associated with Vanda tessellata
TL;DR
Findings demonstrate the growth-promoting potential of metabolites produced by isolate KU/BOT/VT004 and suggest that this endophytic fungus is a promising candidate for future bioinoculant development and orchid propagation, pending further validation through fungal inoculation and colonization studies.
Abstract
Endophytic fungi play an important role in promoting plant growth by producing phytohormones and enhancing nutrient availability; however, their functional roles in orchids remain poorly understood. This study aimed to isolate and functionally characterize plant growth-promoting (PGP) endophytic fungi associated with Vanda tessellata (Roxb.) Hook. ex G.Don. Six representative endophytic fungal isolates were evaluated for plant growth-promoting traits, among which isolate KU/BOT/VT004 exhibited the highest activity. Based on morphological characteristics and ITS rDNA sequence analysis, the isolate was identified as Colletotrichum cf. cobbittiense. The isolate produced high levels of indole-3-acetic acid (35.05 µg/mL), along with ammonia and siderophore activity, indicating strong nutrient-mobilizing potential. Application of the fungal culture filtrate to in vitro-grown protocorms resulted in a two- to three-fold increase in biomass and significantly enhanced chlorophyll content compared with untreated controls. Filtrate-treated protocorms also maintained sustained growth beyond 60 days, whereas nutrient-limited control protocorms exhibited reduced growth. These findings demonstrate the growth-promoting potential of metabolites produced by isolate KU/BOT/VT004 and suggest that this endophytic fungus is a promising candidate for future bioinoculant development and orchid propagation, pending further validation through fungal inoculation and colonization studies.