Pseudomonas And Azospirillum

Pseudomonas strains are fast growing, genetically diverse and metabolically versatile bacteria. Many pseudomonad species are preferential inhabitants of the rhizosphere of plants, reaching up to 10(8) CFU/g of roots for crop species like soybean or maize in the field. Rhizospheric pseudomonads contribute to plant growth and health through a variety of plant probiotic mechanisms, including protection of roots against fungal pathogen attack. Due to their relative ease to isolate and cultivate in the lab, there is an enormous wealth of knowledge about physiological, biochemical, and genetic traits of pseudomonads. Based on their PGPR traits, several inoculant products are commercialized, either for seed, foliar, or postharvest treatment of crops, vegetables, and fruits. Provided that pseudomonads share the rhizosphere niche with Azospirillum species, as well as with many other PGPR microorganisms, combined formulations have also become available for agronomic purposes. However, little information about interspecies and multispecies interactions is available. This chapter describes microbiological, genetic, and agronomic tools that may be applied to isolate and characterize novel Pseudomonas spp. from diverse source materials, to study their interaction with Azospirillum cells in the context of dual or multispecies inoculants, and to evaluate the quality and effectiveness of formulated products.