Chemosensitization of Fusarium graminearum to Chemical Fungicides Using Cyclic Lipopeptides Produced by Bacillus amyloliquefaciens Strain JCK-12.

Kihyun Kim,Chul Won Lee,Gyung Ja Choi,Hokyoung Son,Areum Ha,Jin-Cheol Kim,Theresa Lee,Yin-Won Lee,Ji-In Kim,Hae Woong Park,Ae Ran Park,Nan Hee Yu,Yoonji Lee

doi:10.3389/fpls.2017.02010

Abstract

Fusarium head blight (FHB) caused by infection with Fusarium graminearum leads to enormous losses to crop growers, and may contaminate grains with a number of Fusarium mycotoxins that pose serious risks to human and animal health. Antagonistic bacteria that are used to prevent FHB offer attractive alternatives or supplements to synthetic fungicides for controlling FHB without the negative effects of chemical management. Out of 500 bacterial strains isolated from soil, Bacillus amyloliquefaciens JCK-12 showed strong antifungal activity and was considered a potential source for control strategies to reduce FHB. B. amyloliquefaciens JCK-12 produces several cyclic lipopeptides (CLPs) including iturin A, fengycin, and surfactin. Iturin A inhibits spore germination of F. graminearum. Fengycin or surfactin alone did not display any inhibitory activity against spore germination at concentrations less than 30 μg/ml, but a mixture of iturin A, fengycin, and surfactin showed a remarkable synergistic inhibitory effect on F. graminearum spore germination. The fermentation broth and formulation of B. amyloliquefaciens JCK-12 strain reduced the disease incidence of FHB in wheat. Furthermore, co-application of B. amyloliquefaciens JCK-12 and chemical fungicides resulted in synergistic in vitro antifungal effects and significant disease control efficacy against FHB under greenhouse and field conditions, suggesting that B. amyloliquefaciens JCK-12 has a strong chemosensitizing effect. The synergistic antifungal effect of B. amyloliquefaciens JCK-12 and chemical fungicides in combination may result from the cell wall damage and altered cell membrane permeability in the phytopathogenic fungi caused by the CLP mixtures and subsequent increased sensitivity of F. graminearum to fungicides. In addition, B. amyloliquefaciens JCK-12 showed the potential to reduce trichothecenes mycotoxin production. The results of this study indicate that B. amyloliquefaciens JCK-12 could be used as an available biocontrol agent or as a chemosensitizer to chemical fungicides for controlling FHB disease and as a strategy for preventing the contamination of harvested crops with mycotoxins.

Highlights

Fusarium graminearum causes Fusarium head blight (FHB), a globally devastating fungal disease of small grain cereals, especially on wheat and barley (McMullen et al, 1997)
Our study shows the possibility of B. amyloliquefaciens JCK-12 as an available biocontrol agent for controlling FHB or as a chemosensitizer to improve the sensitivity of chemical fungicides
The results demonstrate that B. amyloliquefaciens JCK-12 has a broad spectrum of antifungal activity and could be used as a biocontrol agent for various plant fungal pathogens used in this analysis

Summary

Introduction

Fusarium graminearum causes Fusarium head blight (FHB), a globally devastating fungal disease of small grain cereals, especially on wheat and barley (McMullen et al, 1997). FHB results in extensive yield loss of grains (Goswami and Kistler, 2004). Due to climate change, it is expected that FHB epidemics will become more severe and further losses in crop yield will occur (Madgwick et al, 2011). FHB reduces the quality and feeding value of crops by producing various toxic metabolites, including trichothecenes and zearalenone mycotoxins. Deoxynivalenol (DON), the most important trichothecene, poses a significant threat to animal health and food safety (Marasas et al, 1984; Joffe, 1986; Snijders, 1990; McMullen et al, 2012) and facilitates disease development by acting as a virulence factor (Desjardins et al, 1996)

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