Culturable fungal endophytes in shoots of Dendrobium aqueum Lindley - An imperiled orchid

Three non-mycorrhizal endophytic fungi were isolated and identified in a threatened epiphytic orchid Dendrobium aqueum Lindley. Stem, leaf and pseudobulb segments obtained from wild plants collected from Kolli hills, Tamil Nadu, India were used to isolate the fungi. Both morphology and molecular sequencing of internal transcribed spacer (ITS) regions of endophytic fungi revealed that all three isolates belonged to the genus Colletotrichum. Endophytes colonization rate was higher on basal stem segments (27.78%) compared to other stem portions, leaves (16.67%) and pseudobulbs (16.67%). All three endophytes showed organ specificity with higher assemblage in stem segments, whereas leaf and pseudobulb segments contained only one endophyte. The wild plants showed no major disease symptoms to affect leaf or plant growth, except few minor dark or grey spots on the mature senescing leaves. Hence, the Colletotrichum isolates were found to be the dominant endophytes of D. aqueum, perceived to have a symbiotic relationship with it, as there were no other fungal isolates found in this study.