Culture-dependency of fungal-endophyte isolation and implications for natural products research
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University of New Brunswick
The assemblage of fungi isolated from plant tissues is dependent on the isolation conditions and cannot be assumed to represent the entire endophytic community. A comparison of the two media most used for endophyte isolation [2.0% malt extract (MEA), and 2.4% potato dextrose (PDA)] using three plants (Pyrola elliptica, Pinus strobus, and Sarracenia purpurea) consistently showed that PDA had a higher isolation frequency of endophytic fungi, and a greater number of morphologically distinct fungi recovered per sampling unit. Estimations of the total number of distinct fungi isolable using PDA also exceeded those for MEA. Culture-independent methods of detecting endophytic fungi were assessed for S. purpurea and revealed an additional fungal species, Penicillium spinulosum, that had not been isolated on PDA or MEA. Extracts of the isolated fungi were evaluated in antimicrobial assays where there was no difference in the proportion of active extracts observed between the two isolation media used.