Effects and possible mechanism of tea tree oil against Botrytis cinerea and Penicillium expansum in vitro and in vivo test.

The purpose of this study was to investigate the antifungal activities and possible mechanisms of tea tree oil (TTO) against Botrytis cinerea and Penicillium expansum in vitro and in vivo. The results show that TTO exhibits dose-dependent antifungal activity against both pathogens, but P. expansum is less sensitive than B. cinerea to TTO not only in the in vitro test but also in artificially inoculated cherry fruits. TTO vapor treatment reduced the decay caused by these pathogens in inoculated cherry fruits, but the effect on P. expansum was less than that on B. cinerea. While the total lipid and ergosterol contents of the cell membrane are greater in P. expansum than in B. cinerea, TTO treatment lowers the total lipid content in the membranes of both species by well over 50%, and ergosterol content is reduced to a greater extent in B. cinerea than in P. expansum. In both pathogens, TTO alters mycelial morphology and cellular ultrastructure. Oxygen consumption measurements show that TTO inhibits respiratory metabolism via the tricarboxylic acid cycle pathway in both pathogens, though more severely in B. cinerea than in P. expansum. The relatively decreased sensitivity of P. expansum to TTO may be due to the fact that TTO causes less disruption of the cell membrane in this organism, and higher inhibition the respiratory metabolism to the extent observed in B. cinerea.