Effect of soil salinity on population structure of fluorescent pseudomonads in spinach rhizosphere

Abstract

Use of PGPR (plant growth-promoting rhizobacteria) for stimulating plant growth and for the biological control of soil-borne diseases is necessary mainly in fields with intensive cropping. The intensive cultivation systems in horticulture have generally led to soil salinity due tp the high rates of fertilizer application. Therefore, the high concentration of inorganic salts accumulated in the plant rhizosphere is likely to be a factor of salinity stress affecting both roots and root-associated rhizobacteria. In a previous report (Matsuguchi and Sakai 1995), we observed that high salinity of soil had induced a significant decrease in the populations of fluorescent pseudomonads in spinach roots. Furthermore, the adverse effect of high salinity of soil was more pronounced on Pseudomonas fluorescens strains than on Pseudomonas putida strains, resulting in an alteration of the composition of fluorescent pseudomonads in the roots where vP. putida} predominated. The objective of the present study was to determine the effect of soil salinity on the population structure, at the strain level, of fluorescent pseudomonad species colonizing spinach roots.