The Antifungal Effect of Garlic Essential Oil on Phytophthora nicotianae and the Inhibitory Component Involved.

Yaochen Wang,Keke Wei,Jianyu Gou,Yanfen Zheng,Jianmin Chao,Cheng-Sheng Zhang,Fanyu Kong,Xiaobin Han,Donglin Zhao

doi:10.3390/biom9100632

Abstract

This study explored the chemical compositions of garlic essential oil, the inhibitory activity of garlic essential oil and diallyl disulfide (DADS) against Phytophthora nicotianae, and the effects on mycelial plasma membrane permeability and P. nicotianae inhibition. In total, 29 compounds were detected in garlic essential oil, of which 26 were detected by gas chromatography‒mass spectrometry (GC-MS) and 21 by headspace solid-phase microextraction (HS-SPME) GC-MS. DADS (60.12% and 19.09%) and trisulfide di-2-propenyl (14.18% and 17.98%) were the major components identified by HS-SPME GC-MS and GC-MS analysis, respectively. Half-inhibitory concentration (Ec50, antagonism) and minimum inhibitory concentration (MIC, fumigation) of DADS against P. nicotianae were 150.83 μL/L and 20 μL/L, respectively, while Ec50 of garlic essential oil was 1108.25 μL/L. Mycelial membrane permeability gradually increased in a concentration-dependent manner, and cell death increased at 450 μL/L DADS. Furthermore, DADS treatment significantly reduced the incidence of tobacco black shank and the number of P. nicotianae pathogens in rhizosphere soil. DADS also promoted root development of tobacco seedlings at low concentrations, which was inhibited at high concentrations. Therefore, DADS may play an important role in the antifungal effect against P. nicotianae by destroying mycelial cell membrane integrity, causing an increase in cell membrane permeability, and leading to cell death.

Highlights

Tobacco black shank is a critical, global, soil-borne disease caused by Phytophthora nicotianaeBreda de Haan [1] that has a high incidence and wide distribution range, and is highly destructive.In China, the epidemic area of the disease is more than 76,372 hectares, and the direct economic loss is over $1 billion annually
The identification of essential oil components was based on the calculated retention indices (RI) and
Results indicated that garlic essential oil and its primary constituent had a good inhibitory effect on tobacco black disease caused by P. nicotianae

Summary

Introduction

In China, the epidemic area of the disease is more than 76,372 hectares, and the direct economic loss is over $1 billion annually. Chemical fungicides such as metalaxyl-mancozeb are the main control method, which can cause several issues, including high pesticide residues in tobacco leaves, environmental pollution, and pathogen resistance to fungicides [2]. Biomolecules 2019, 9, 632 have antimicrobial and antioxidant properties [3,4,5,6] Compounds such as terpenes and terpenoids have demonstrated antifungal activity and are degraded [7,8]. EOs are potential natural alternatives to reduce the negative impact of synthetic fungicides

Methods

Results

Conclusion