Bacterial Antagonists to Verticillium dahliae Kleb.

Bacteria were isolated from the rhizosphere of Verticillium dahliae hosts and from environments. A total of 1394 bacterial isolates were screened for their ability to inhibit in vitro the growth of the phytopathogenic fungi V. dahliae ; 15% (203 of the isolates) showed antifungal effects. Seventeen isolates were selected and determined for further investigations, seven different species were identified. Several of the bacterial species listed, e.g. Erwinia herbicola, Pseudomonas chlororaphis, Pseudomonas paucimobilis and Xanthomonas maltophilia have not been reported previously as bacterial antagonists of V. dahliae. Bacillus subtilis, Pseudomonas fluorescens and Xanthomonas maltophilia are strong antagonists. We proved that lytic enzymes and siderophores are involved in the inhibition of growth. Ultrastructural and morphological changes were induced in Verticillium dahliae by the antagonistic bacteria.