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 dosedependent 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.

本研究旨在体外和体内研究茶树油（TTO）对灰葡萄孢菌和扩展青霉菌的抗真菌活性及其可能的作用机制。结果表明，TTO对这两种病原菌均表现出剂量依赖性的抗真菌活性，但无论是在体外试验还是在人工接种的樱桃果实中，扩展青霉菌对TTO的敏感性均低于灰葡萄孢菌。TTO蒸汽处理减少了接种樱桃果实中由这些病原菌引起的腐烂，但对扩展青霉菌的效果不如对灰葡萄孢菌的效果明显。虽然扩展青霉菌细胞膜的总脂质和麦角固醇含量高于灰葡萄孢菌，但TTO处理使两种菌细胞膜的总脂质含量降低了50%以上，且灰葡萄孢菌中麦角固醇含量的降低程度大于扩展青霉菌。在这两种病原菌中，TTO改变了菌丝形态和细胞超微结构。耗氧量测定表明，TTO通过三羧酸循环途径抑制了两种病原菌的呼吸代谢，不过对灰葡萄孢菌的抑制作用比对扩展青霉菌更严重。扩展青霉菌对TTO相对较低的敏感性可能是由于TTO对该菌细胞膜的破坏较小，以及对呼吸代谢的抑制程度不如在灰葡萄孢菌中观察到的那么高。