Isolation and characterization of antagonists for the biocontrol of the postharvest wound pathogen Botrytis cinerea on strawberry fruits

Antagonistic bacteria and yeasts were isolated from the epiphytic flora of stored strawberry fruits and evaluated for their ability to protect strawbe rry fruit wounds after harvest against Botrytis cinerea. Among selected pot ential antagonists, three strains of Candida reukaufii (5L3, 10CL4, 10L2) a nd one strain of Candida pulcherima (10L8) still protected fruit wounds whe n applied at 10(3) CFU/wound, reducing lesion or conidiophore development. In the same conditions, two Enterobacteriaceae (10B1, 5B4) highly reduced p athogen development. Strain 5B4 was still highly inhibitory when inoculated at 10(2) CFU/wound. The six strains applied on fruits did not produce any significant change in color, brightness, and firmness of fruits. The two ye asts, 5L3 and 10L8, and particularly the two bacteria, 5B4 and 10B1, were s elected for further studies. The four antagonists effectively colonized fru it wounds and strongly inhibited spore germination of B, cinerea in vitro. The bacterial cells surrounded the germinating spores of B. cinerea and att achment of 5L3 cells on germinating spores were additionally observed. Bact erial antagonists, particularly the strain 5B4, multiplied and rapidly used carbohydrates in strawberry fruit juice despite the low pH (pH 3.5). The e fficiency of the bacterial antagonists on fruit wounds was related to their growth and nutritional properties.