Khaledi N, Taheri P, Tarighi S
Department of Crop Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
J Appl Microbiol. 2015 Mar;118(3):704-17. doi: 10.1111/jam.12730. Epub 2015 Jan 9.
The main objective of this study was to investigate the effect of various essential oils (EOs) to decrease the activity of cell wall degrading enzymes (CWDEs) produced by fungal phytopathogens, which are associated with disease progress. Also, effect of seed treatment and foliar application of peppermint EO and its main constituent, menthol, on diseases caused by two necrotrophic pathogens on bean was investigated.
Antifungal activity of EOs on Rhizoctonia solani and Macrophomina phaseolina, as bean pathogens, was evaluated. The EOs of Mentha piperita, Bunium persicum and Thymus vulgaris revealed the highest antifungal activity against fungi. The EO of M. piperita had the lowest minimum inhibitory concentration (MIC) for R. solani among the three EOs tested. This pathogen did not grow in the presence of M. piperita, B. persicum and T. vulgaris EOs at 850, 1200 and 1100 ppm concentrations, respectively. The B. persicum EO had the lowest MIC for M. phaseolina as this fungus did not grow in the presence of M. piperita, B. persicum and T. vulgaris EOs at concentrations of 975, 950 and 1150 ppm, respectively. Hyphae exposed to EOs showed structural changes. Activities of cellulase and pectinase, as main CWDEs of pathogens, decreased by EOs at low concentration without effect on fungal growth. Seed treatment and foliar application of peppermint EO and/or menthol significantly reduced the development of bean diseases caused by both fungi. Higher capability of menthol than peppermint EO in decreasing diseases on bean was observed.
Reducing CDWEs activity is a mechanism of EOs' effect on fungi. Higher antifungal activity of menthol compared to peppermint EO was observed not only in vitro but also in vivo.
Effect of EOs on CWDEs involved in pathogenesis is described in this study for the first time. Menthol can be used as a botanical fungicide to control destructive fungal diseases on bean.
本研究的主要目的是调查各种精油（EOs）对降低与病害进展相关的真菌植物病原体产生的细胞壁降解酶（CWDEs）活性的影响。此外，还研究了薄荷精油及其主要成分薄荷醇的种子处理和叶面喷施对豆类上两种坏死性病原菌引起的病害的影响。
评估了EOs对豆类病原菌立枯丝核菌和菜豆壳球孢菌的抗真菌活性。薄荷、孜然和百里香的精油对真菌显示出最高的抗真菌活性。在所测试的三种精油中，薄荷精油对立枯丝核菌的最低抑菌浓度（MIC）最低。在分别为850、1200和1100 ppm浓度的薄荷、孜然和百里香精油存在下，该病原菌不生长。孜然精油对菜豆壳球孢菌的MIC最低，因为在分别为975、950和1150 ppm浓度的薄荷、孜然和百里香精油存在下，这种真菌不生长。暴露于精油的菌丝显示出结构变化。作为病原体主要CWDEs的纤维素酶和果胶酶的活性在低浓度精油作用下降低，而对真菌生长无影响。薄荷精油和/或薄荷醇的种子处理和叶面喷施显著降低了两种真菌引起的豆类病害的发生。观察到薄荷醇在降低豆类病害方面比薄荷精油具有更高的能力。
降低CDWEs活性是精油对真菌作用的一种机制。不仅在体外而且在体内都观察到薄荷醇比薄荷精油具有更高的抗真菌活性。
本研究首次描述了精油对参与发病机制的CWDEs的影响。薄荷醇可作为一种植物杀菌剂来控制豆类上的毁灭性真菌病害。
