Rizosphere colonization by Plant Growth promoting Bacteria

SILVINA L. LÓPEZ- GARCÍA; MARÍA FLORENCIA LÓPEZ

Bacterial Populations: Basic and Applied Aspects of Their Structure and Evolution

Research Signpost/ Transworld Research Network

Lugar: Kerala; Año: 2010; p. 161 - 192

 The rhizospheric environment differs from the rest of the soil thanks to the influence exerted by diverse root activities, which can extend to several millimeters from the plant surface. The root influence is decisive for microorganisms multiplication and diversification associated to this zone. Here diverse compounds such as sugars, organic acids, aminoacids, and secondary metabolites are excreted and exuded giving rise to a selective nutrient enrichment. Moreover, plant species may differ in the metabolite profiles released in their rhizospheres, and a single plant also may release different compounds throughout its root. Consequently, microbial populations composition associated to rhizospheres usually varies among plant species and different root zones of a single plant. In this chapter we resume the main kinas and beneficial characteristics of microorganisms that colonize the rhizosphere, collectively known as plant growth promoting rhizobacteria (PGPR). This group includes free-living or symbiotic N2 fixers, phosphorus solubilizers, phytopathogenic antagonists, and microorganisms able to synthesize and release plant growth regulators among others. Since it is desirable to favor the establishment of PGPR in agriculturally important crop rhizospheres, factors influencing its colonization need to be understood.