Abstract
Pseudomonas species have been widely studied as biological agents (BCAs) and it is alternative to the application of chemical fungicides. Our objective was to optimize nutritional and environmental conditions of the isolated Pseudomonas fluorescens fp-5 for biomass and metabolites production and to evaluate itsagainst the grey mould disease caused by Botrytis cinerea on strawberry plants under field conditions. Pseudomonas fluorescens, showed antagonistic properties, in vitro, against thepathogen Botrytiscinerea. Effect of the separated secondary metabolites on the fungal growth by broth dilution technique and antifungal activity by agar well diffusion technique was studied. Response surface methodology was used to investigate the effects of four fermentation parameters (pH, incubation time, carbon and nitrogen concentrations) on biomass and bioactivemetabolites [antibiotic phenazin and siderophore] production. Glycerol was found to be the best carbon source for improved biomass and metabolites production. Meanwhile, peptone and yeast extract were found to be the best nitrogen source. Analysis of each formulation revealed that glycerol oil at 0.01% the best oil used for protect P. fluorescens for 3 months Under natural condition, P. fluorescens formulation was effective in reducing B. cinerea disease in strawberry leaves and fruits. Pre-harvest treatment protected fruits from Botrytis post-harvest disease in comparing of fungicide. In addition, the obtained results showed that bacterial treatment significantly increased thegrowth parameters as well as dry weights and yield.
Highlights
Botrytis fruit rot is caused by the fungus Botrytis cinerea and is the most important disease of strawberry worldwide and in Egypt [1]
Pseudomonas species have been widely studied as biological agents (BCAs) and it is alternative to the application of chemical fungicides
The production of phenazine1-carboxylate and Siderophore increased by increasing the glycerol concentration till 1.5% v/v decreased again
Summary
Botrytis fruit rot (gray mold) is caused by the fungus Botrytis cinerea and is the most important disease of strawberry worldwide and in Egypt [1]. The disease can cause important fruit losses on strawberry plants before or after harvest worldwide and it is estimated that they can cause yield losses up to 50% for untreated strawberries [2,3,4]. Siderophores, whose chemical structures depend upon their producer microorganism, may provide iron (III) to some vegetable cells. These metabolites, due to their antagonistic capability against pathogenic microorganisms, could act as growth factors in plants [7]. Other desirable features for a potent organism are that it should have the ability to synthesize anti-fungal metabolites, such as the antibiotic phenazin
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