Biocontrol-based selection and characterization of pseudomonads from rhizosphere and soil samples from no-tillage plots in Argentina

AGARAS, B; SCANDIANI M; LUQUE A; CARMONA M; FERNANDEZ L; WALL LG; VALVERDE C

Workshop; 9th International and 1st Latinamerican PGPR Workshop; 2012

Members of the Pseudomonas genus colonize the rhizosphere of different plant species and display plant-probiotic traits. Therefore, they are interesting candidates for biological agricultural inputs to stimulate plant development and/or promote crop health. As members of a multidisciplinary consortium dedicated to study soil biology in relation to crop productivity under sustainable agricultural management (BIOSPAS), we search for plant-probiotic pseudomonads already adapted to local conditions. In particular, we focus on isolates able to inhibit the growth of emerging fungal pathogens recovered from extensive crops cultivated under no-till regime. To this end, about 100 isolates from soil and rhizosphere samples were chosen by their differential growth aspect on the pseudomonads selective medium S1. A first selection step was a qualitative screening of antagonistic activity against 12 fungal pathogens. 20 isolates confirmed their antagonistic potential in quantitative individual assays. Their taxonomic position was determined by partial sequencing of 16S rDNA and oprF genes. In vitro assays showed that among the 20 isolates, 45% produced HCN, 95% secreted proteases, 30% were phzF+ (for phenazine synthesis) and 10% were phlD+ (for DAPG synthesis). In addition, 10% could grow on ACC as the sole N source, 50% produced IAA and 50% solubilized hydroxyapatite. A collection of Pseudomonas isolates with in vitro plant-probiotic traits was built. In planta assays are required to test their biocontrol and PGPR potential