BIOCHEMICAL CHARACTERIZATION OF ANTAGONISTIC PSEUDOMONAS FLUORESCENS STRAINS INVOLVED IN BIOLOGICAL CONTROL OF BROWN SPOT OF PEAR
J ALEMANY, A BONATERRA, J CAMPS, E MONTESINOS
Institute of Food and Agricultural Technology-CERTA, University of Girona, Avda. Luis Santala, s/n. 17003, Girona, Spain
Background and objectives Several strains of Pseudomonas fluorescens and Erwinia herbicola were isolated from a wide range of environments and were characterized for their in vitro antagonism to Stemphylium vesicarium, the causal agent of brown spot of pear, Penicillium expansum and other plant pathogens. These strains were grouped in relation to the utilization of several nutritional media, and to their antagonistic capacity. These strains have been also characterized in their ability to produce cyanide and it has been correlated to their antagonistic capacity, biovar and origin. The aim of this work was to characterize the production of antifungal metabolites produced by the most antagonistic strains P. ;fluorescens EPS288 and P. ;fluorescens EPS375.
Materials and methods Different growth conditions such as temperature and growth media have been assayed in order to determine the pattern of cyanide production by the strain EPS288. Cyanide was detected by the alcaline picrate and spot test methods. Culture supernatants and the extracts resulting from an organic solvent extraction of some media where the strain EPS375 has grown, have been assayed for antifungal activity against S. ;vesicarium and P. ;expansum by different bioassay tests .
Results and conclusions