Effect of substrate on the bioactivity of volatile antimicrobials produced by Muscodor albus

Muscodor albus, a newly described endophytic fungus, inhibits and kills other fungi and bacteria by emitting volatile organic compounds (VOCs) with antibiotic properties. The composition of the medium used to support the growth of this fungus greatly influences the quality and effectiveness of the volatiles emitted by this organism. A sucrose enriched medium primarily yielded methyl isobutylketone and acetic acid, butyl ester as the primary volatiles, yet neither of these compounds appeared in any other medium. More enriched media were more effective in inhibiting a suite of plant pathogens used as test microbes. A mixture of propanoic acid, 2-methyl-, and several related esters were associated with the elevated bioactivity of these fungal support media. An artificial mixture of the volatile compounds emitted by the M. albus on the various growth media mimicked the effects of the natural volatiles in the bioassay test system. Both IC50 and IC100 values, for each test organism, were generally the lowest for the artificial test mixture representing the atmosphere of the fungus grown on PDA. Both natural and artificial mixtures of volatiles effectively served as mycofumigants of various naturally and artificially fungal contaminated seeds in closed chambers. A wide range of pathogenic seed associated fungi including aspergillus, penicillum, fusarium and leptosphaeria are controlled by the gases of M. albus. (C) 2003 Elsevier Ireland Ltd. All rights reserved.