Biological control of grey mould in strawberry fruits by halophilic bacteria

Abstract

Aims: Grey mould caused by Botrytis cinerea is an economically important disease of strawberries in Tunisia and worldwide. The aim of this study was to select effective halophilic bacteria from hypersaline ecosystems and evaluate the abilities of antifungal bacteria to secrete extracellular hydrolytic enzymes, anti‐Botrytis metabolites and volatiles. Methods and Results: Grey mould was reduced in strawberry fruits treated with halophilic antagonists and artificially inoculated with B. cinerea. Thirty strains (20·2%) were active against the pathogen and reduced the percentage of fruits infected after 3 days of storage at 20°C, from 50% to 91·66%. The antagonists were characterized by phenotypic tests and 16S rDNA sequencing. They were identified as belonging to one of the species: Virgibacillus marismortui, B. subtilis, B. pumilus, B. licheniformis, Terribacillus halophilus, Halomonas elongata, Planococcus rifietoensis, Staphylococcus equorum and Staphylococcus sp. The effective isolates were tested for antifungal secondary metabolites. Conclusions: Moderately halophilic bacteria may be useful in biological control against this pathogen during postharvest storage of strawberries. Significance and Impact of the study: The use of such bacteria may constitute an important alternative to synthetic fungicides. These moderate halophiles can be exploited in commercial production and application of the effective strains under storage and greenhouse conditions.

Characterization of a novel chitinase from a moderately halophilic bacterium, Virgibacillus marismortui strain M3-23

“…The morphological, physiological and molecular characteristics of this strain were previously reported and its nucleotide sequence of 16S rDNA has been deposited in the GenBank database under the accession number GQ2825501 as previously described (Essghaier et al 2009). …”

“…Chitinase activity was determined according to the method of Gomez Ramirez et al (2004) as previously detailed (Essghaier et al 2009(Essghaier et al , 2010. A 1:1 mixture (v/v) of cell free supernatant and 10% (w/v) colloidal chitin in 0.2 M phosphate buffer pH 7 was incubated for 1 h at 50°C.…”

“…A new strain of moderately halophilic bacterium Virgibacillus marismortui strain M3-23 was isolated from a Tunisian shallow salt lake (Essghaier et al 2009). The morphological, physiological and molecular characteristics of this strain were previously reported and its nucleotide sequence of 16S rDNA has been deposited in the GenBank database under the accession number GQ2825501 as previously described (Essghaier et al 2009).…”

“…However, our laboratory was the first to take an interest in the study of antifungal chitinase from moderately halophilic bacteria such as Virgibacillus marismortui, Terribacillus halophilus and Planococcus rifitoensis. These moderately halophilic bacteria were isolated previously from shallow salt lakes in Tunisia and selected as strong antagonists of Botrytis cinerea-the causal agent of grey mold disease on strawberries and tomatoes under the commercial standard conditions applied in Tunisia (Essghaier et al 2009;Sadfi-Zouaoui et al 2008).…”

“…Previous research also aimed to identify the mode of action of the most successful isolates as this information may help optimize their biocontrol efficiency in the field. Understanding the mechanisms involved in biological control may enable efficacy to be enhanced (Sadfi-Zouaoui et al 2008;Essghaier et al 2009). We reported previously the efficiency of the moderately halophilic Virgibacillus marismortui strain M3-23 in biological control, and its high production of chitinase.…”