CONICET | Buscador de Institutos y Recursos Humanos

Introduction Actinomycetes are bacteria frequently found in a variety of soils, and they constitute a substantial component of microbiota. These microorganisms produce enzymes and extracellular metabolites with different biological activities, and strongly contribute to the decomposition of biopolymers and recalcitrant substances. Some actinobacteria are able to colonize plant inner tissues, eliciting either beneficial or pathogenic effects. Some studies have found PGPR features also on actinomycetes isolated from rhizosphere and rhizoplane. Objectives To delve into the characterization of ten non-Frankia isolates from agricultural soils, seeking to elucidate the strategies that cause the plant growth promoting effects showed by such isolates in greenhouse experiments. Materials and methods From a collection of actinomycete strains isolated from Glicine max rhizosphere and rhizoplane at three locations of the central agricultural region of Argentina, and after co-inoculation assays performed in soybean between each isolate and the symbiont Bradyrhizobium japonicum, we selected 10 isolates belonging to the genera Streptomyces and Streptosporangium, according to morphological criteria and positive effects on plant growth. In order to obtain further detail about their identity, we isolated genomic DNA and sequenced the gene encoding the 16S rRNA of each isolate. We evaluated the capability of these microorganisms to grow in absence of N, by means of their development on NFb medium in solid, semi-solid and liquid formats. We look at the nifH gene by PCR. Moreover, we conducted compatibility tests of the isolates with each other, with Bradyrhizobium japonicum, and with an antifungal substance used commercially, and we also conducted tests to evaluate the ability of these organisms to antagonize phytopathogenic fungi. Results We were able to identify the isolates at the species level. We observed morphological differences for the isolates, depending on the absence or presence of N in NFb medium. Some early results suggested the presence of nifH gene on two of these isolates. All isolates showed good compatibility between each other, with Bradyrhizobium japonicum, and with the antifungal substance. They also showed different degrees of activity to antagonize one or more pathogenic fungi. Conclusion Other tests, such ARA and immunodetection of Dinitrogenase are needed and will be tried in order to confirm these isolates? ability to fix N2. Results we here obtained raise great perspectives for the use of these actinomycetes in agroindustry.