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.

In the present study, we firstly aimed to determine the ability of halophilic bacteria to improve tomato growth. as well as to detect the antimicrobial activities from two moderately halophilic bacteria strain M3-23 of Virgibacillus marismortui and strain J31 of Terribacillus halophilus exhibited by their intracellular proteins. The results showed that both bacteria were able to improve stem tomato growth by comparison of untreated tomato. The halophilic bacteria were also able to produce intracellular antifungal enzyme: glucanase produced by V. marismortui (1.74U/mg) and chitinase (39.39U/mg) produced by T. halophilus. Both chitinases were halotolerants (active in the presence of (0% to 30% NaCl (w/v)). Chitinase produced by strain J31 was alcaline (pH optimum pH 12), but chitinase from strain M3-23 was acidic (pH 4 optimum) more than 90% and 80% of activities were retained in the presence of pH value from 4 to 12, respectively for strain J31 and M3-23. Both enzymes were thermotolerants; optimum temperature was 80°C and 90°C respectively for strain J31 and strain M3-23. Both strains have lysozyme activity and value ranging from 6.6 U/ml to 6.8 U/ml respectively for strain J31 and strain M3-23. On the whole, the most potent in vitro antifungal effect was demonstrated by intracellular compound produced by strain J31 compared to strain M3-23. This study, was the first showing the antimicrobial efficiency of moderately halophilic bacteria by means of their intracellular compounds, by means of the spore germination reduction and the destroy of mycelial growth of Botrytis cinerea, in vitro. The distinguishable characteristics of their intracellular halotolerant and thermotolerant chitinases make them as good candidates for biotechnological applications.