In Vitro Antifungal Activity of Burkholderia gladioli pv. agaricicola against Some Phytopathogenic Fungi

Hazem Elshafie,Ippolito Camele,Rocco Racioppi,Sabino Bufo,Laura Scrano,Nicola Iacobellis

doi:10.3390/ijms131216291

Hazem Elshafie, Ippolito Camele + Show 4 more

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https://doi.org/10.3390/ijms131216291

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Abstract

The trend to search novel microbial natural biocides has recently been increasing in order to avoid the environmental pollution from use of synthetic pesticides. Among these novel natural biocides are the bioactive secondary metabolites of Burkholderia gladioli pv. agaricicola (Bga). The aim of this study is to determine antifungal activity of Bga strains against some phytopathogenic fungi. The fungicidal tests were carried out using cultures and cell-free culture filtrates against Botrytis cinerea, Aspergillus flavus, Aspergillus niger, Penicillium digitatum, Penicillium expansum, Sclerotinia sclerotiorum and Phytophthora cactorum. Results demonstrated that all tested strains exert antifungal activity against all studied fungi by producing diffusible metabolites which are correlated with their ability to produce extracellular hydrolytic enzymes. All strains significantly reduced the growth of studied fungi and the bacterial cells were more bioactive than bacterial filtrates. All tested Bulkholderia strains produced volatile organic compounds (VOCs), which inhibited the fungal growth and reduced the growth rate of Fusarium oxysporum and Rhizoctonia solani. GC/MS analysis of VOCs emitted by strain Bga 11096 indicated the presence of a compound that was identified as 1-methyl-4-(1-methylethenyl)-cyclohexene, a liquid hydrocarbon classified as cyclic terpene. This compound could be responsible for the antifungal activity, which is also in agreement with the work of other authors.

Highlights

The biological control of plant diseases, insects and nematodes by microorganisms has been proposed as an alternative or a supplement to chemical control [1,2]
A preliminary experiment was carried out to evaluate in the dual plate assay the ability of four B.g. pv. agaricicola strains and of their respective culture filtrates to inhibit the growth of the phytopathogenic and plant-associated fungi B. cinerea, A. flavus, A. niger, P. digitatum, P. expansum, S. sclerotiorum and P. cactorum
Burkholderia gladioli pv. agaricicola is an important pathogen in the mushroom industry; it causes soft rot of Agaricus bitorquis and

Summary

Introduction

The biological control of plant diseases, insects and nematodes by microorganisms has been proposed as an alternative or a supplement to chemical control [1,2]. The biological control activity of several bacteria is exerted either directly through antagonism of pathogen development, or indirectly by eliciting a plant-mediated resistance response [3]. Mechanisms responsible for antagonistic activity include: inhibition of the pathogen growth; competition for colonization sites, nutrients and minerals; parasitism; and, mycophagy [4,5,6]. It is a common strategy of bacterial antagonists to inhibit the plant pathogens by excretion of antimicrobial metabolites (AMMs). It was demonstrated that volatile organic compounds (VOCs), including hydrocarbons, alcohols, ketones, aldehydes, ethers, esters, terpenes, terpene derivatives, and several heteroaromatic compounds produced by some bacteria can influence the growth of fungi [8,9,10]

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