Effect of cations on the growth of fluorescent pseudomonad isolates from spinach roots grown in soils with different salinity levels

Abstract

Effect of Inorganic ion concentrations in culture solution on the growth of Pseudomonas putida and P. fluorescens Isolates from spinach roots grown in soils with high-salinity (H-soil) and low-salinity (L-soil) levels was investigated. Both H- and L-soils were taken from the topsoil of a greenhouse for spinach cultivation and a nearby fallow field, respectively. In the H-soil inorganic ions had accumulated due to the high rates of application of fertilizer. Among the ions, the concentrations of Ca2+, NO3, and SO42in the H-soil were significantly higher than those in the L-soil. Among the inorganic ions tested (K+, Na+, Ca2+, Mg2+, Cl, NO3, and SO42), Ca2+was found to be the most inhibitory on the growth of isolates. In addition, the isolates from the H-soil were more Ca2+-tolerant than those from the L-soil. Consequents the growth tolerance to Ca2+stress of the total 80 isolates, 40 each from the H-soil and L-soil, was compared at 150 mM Ca2+. Most isolates from the H-soil showed a significantly higher tolerance. The higher tolerance to Ca2+of the isolates from the H-soil may have been acquired through selection under increasing Ca2+stress in the field. The Ca2+tolerance of the fluorescent pseudomonad strains may account for their survival and root-colonizing activity in soils with Ca2+accumulation. © Taylor & Francis Group, LLC.