The velamen roots in epiphytic orchids are rather complex, and their environmental role remains poorly understood. Fungal associates are known in the velamen roots of tropical orchids, but the magnitude of their diversity in particular species remains unknown. The primary aim of this work was to explore endophytic fungal species associated with the velamen roots of three tropical epiphytic orchids. Velamen roots were collected from 30 plants of Rhynchostylis retusa and 25 plants each of Epidendrum radicans and Oncidium sphacelatum. Endophytic fungi were isolated from 2160 segments. Twenty species of velamen-root-associated fungal endophytes were separated with a culture technique. The isolated strains were grouped into morphotypes, subsequently identified morphologically and by means of ITS DNA barcoding. Ascomycota were the dominant group with 18 species. Trichoderma cf. asperellum, Endomelanconiopsis endophytica, Trichoderma cf. atroviride and Lasiodiplodia theobromae were the most frequent taxa isolated. A majority of the identified fungi were common to more than one orchid. Colonisation rate, isolation rate, Shannon-Wiener diversity index, species richness and species evenness of the endophytic fungi from different orchids were studied and were tested for significance with the Kruskal-Wallis H test. The colonisation rate and isolation rate of fungal associates in the velamen roots were found to be distinctly the lowest in Rhynchostylis retusa.
Deepthi A. S., Ray J. G. (2021): Ecological relevance of the endophytic fungal diversity in velamen roots of tropical epiphytic orchids. – Czech Mycology 73(1): 91–108.
