Antagonistic action of Bacillus subtilis strain SG6 on Fusarium graminearum.

Yueju Zhao,Huimin Song,Yang Liu,Jonathan Nimal Selvaraj,Lichao Sun,Lu Zhou,Fuguo Xing,Yawa Minnie Elodie Folly,Xinxin Tan,Lancine Sangare,Yan Wang,Adam Driks

doi:10.1371/journal.pone.0092486

Abstract

Fusarium graminearum causes Fusarium head blight (FHB), a devastating disease that leads to extensive yield and quality loss of wheat and barley. Bacteria isolated from wheat kernels and plant anthers were screened for antagonistic activity against F. graminearum. Based on its in vitro effectiveness, strain SG6 was selected for characterization and identified as Bacillus subtilis. B. subtilis SG6 exhibited a high antifungal effect on the mycelium growth, sporulation and DON production of F. graminearum with the inhibition rate of 87.9%, 95.6% and 100%, respectively. In order to gain insight into biological control effect in situ, we applied B. subtilis SG6 at anthesis through the soft dough stage of kernel development in field test. It was revealed that B. subtilis SG6 significantly reduced disease incidence (DI), FHB index and DON (P≤0.05). Further, ultrastructural examination shows that B. subtilis SG6 strain induced stripping of F. graminearum hyphal surface by destroying the cellular structure. When hypha cell wall was damaged, the organelles and cytoplasm inside cell would exude, leading to cell death. The antifungal activity of SG6 could be associated with the coproduction of chitinase, fengycins and surfactins.

Highlights

Fusarium graminearum causes Fusarium head blight (FHB), a widespread destructive disease of small grained cereals, resulting in yield loss [1,2,3]
The objective of the present study was to (1) evaluate inhibitory effect of B. subtilis strain SG6 on F. graminearum mycelial growth, sporulation and DON production; (2) determine the antagonistic efficacy of B. subtilis strain SG6 in controlling FHB in field condition; (3) examine the ultrastructural alterations occurring in hypha cells of F. graminearum during interaction with B. subtilis SG6 by transmission electron microscopy (TEM) and scanning electron microscope (SEM); (4) analyze antifungal peptides to investigate the putative biocontrol mechanism
According to 16S rRNA gene sequence analysis, it was found that the closest relatives of strain SG6 were B. subtilis subsp. subtilis NCIB 3610 (99.72%) and B. siamensis KCTC 13613 (99.72%)

Summary

Introduction

Fusarium graminearum causes Fusarium head blight (FHB), a widespread destructive disease of small grained cereals, resulting in yield loss [1,2,3]. FHB causes the reduction of grain quality, by producing a range of toxic metabolites, especially deoxynivalenol (DON) which poses a serious threat to animal health and food safety [4,5]. The use of host resistance is an economically and environmentally effective strategy for controlling FHB. Due to the growing cost of chemical pesticides and increasing awareness about their negative effect, the farmers are looking for alternative substitutes for these products to fulfill the consumers demand on pesticide-free food while maintaining environmental safety

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Conclusion