Analysis of Pseudomonas syringae Populationsand Identification of Strains as PotentialBiocontrol Agents Against Postharvest Rot of Different Fruits

摘要

A collection of Pseudomonas syringae strains was evaluated for in vitroand in vivo growth inhibition of a broad spectrum of bacteria and fungi, forproduction of hydrolytic enzymes, presence of syrB gene and for pathogenicity ondetached fruits and then they were genetically characterized by ARDRA, ERIC-PCR and fAFLP. P syringae strains and their culture filtrates inhibited a wide range of phytopath-ogenic bacteria and fungi in vitro and the inbibition depended on the bacterial andfungal strain. The cell-wall degradation enzymes N-acetyl-β-D-glucosaminidase(NAGase), β-glucosidase, cellobiohydrolase, cellulase and protease were detectedin culture filtrates of the majority of strains while only a few strains showed chiti-nase and glucanase activities. The antagonistic activity in vivo of P syringae strains –evaluated on wounded lemon, orange and mandarin fruits against Penicilliumdigitatum, on apples against P expansum, on grape berries against Botrytis cinerea –was apparent for some of the strains evaluated. P syringae strains isolated fromCitrus spp., pear and strelitzia were moderately to highly pathogenic on testeddetached citrus fruits. All syringae strains showed the presence of syrB gene and their molecularcharacterization with ARDRA, ERIC-PCR and fAFLP allowed their clustering indistinct groups. A partial correlation between groups delineated on the basis ofantagonistic activity in vitro and genomic fingerprints was also apparent. FluorescentAFLP analysis also produced characteristic profiles for each strains useful for riskassessment, monitoring and identification of released antagonistic strains.