Exploiting natural biodiversity within wild olives havens for selecting rhizobacteriawith antagonistic potential against Verticillium dahliae Kleb.

Abstract Wild olive trees (Olea europaea subsp. sylvestris) are considered an important andunexplored source of genetic variability for traits of agronomic and biotechnological interest suchas reservoirs of specific and well adapted rhizobacteria antagonistic to Verticillium dahliae, thecausal agent of Verticillium wilt, the most important disease of cultivated olive worldwide. Apolyphasic approach was used by determining the structure and diversity of bacterialcommunities in the rhizosphere soil and roots of 17 samples of wild olives havens in Cádiz, andCórdoba provinces in the Andalusia region at southern Spain. Results of FT-RFLP patterns of16S rDNA sequences revealed a high heterogeneity of bacterial community compositionsuggesting the existence of plant genotype-site specific factors. By culture-dependent approach,675 culturable bacterial isolates were selected and 94 of them (14%) showed different levels ofantagonistic activity against the defoliating pathotype of V. dahliae as well as production ofdifferent enzymes and secondary metabolites. 16S rDNA gene sequences identified most of thosestrains as Pseudomonas and Bacillus spp.