The Effect of Pseudomonas fluorescens and Pseudomonas putida on Some Soil Biological Properties and Plant Growth Indices of Wheat under Salt Stress

In order to study the effect of Pseudomonas fluorescens and P. putida on some soil biological properties and growth indices of wheat under salt stress and some of soil chemical and biological indices, a factorial experiment based on completely randomized design with three replications was conducted. The factors were salinity at four levels, control, 6, 8 and 10 dS/m, and inoculation with plant growth promoting rhizobacteria at three level, including no-inoculation, inoculation with Pseudomonas putida and inoculation with Pseudomonas fluorescens. The results showed that soil salinity significantly decreased plant yield parameters such as root volume, root fresh and dry weight, shoot fresh and dry weight, chlorophyll a, chlorophyll b, total chlorophyll and also the inoculation with Pseudomonas bacteria significantly increased these indices. Also, there was a significant difference between two Pseudomonas strains, however in general it was not possible to precisely compare two bacteria. On the other hand, the results showed that with increasing the salinity level, factors of soil biological properties such as microbial biomass carbon, basal respiration and substrate-induced respiration reduced and the use of bacteria has increased these traits. Regarding the soil biological indices that increased with the inoculation, it can be concluded that the inoculation indirectly increased soil biological indices by affecting plant growth and yield. Therefore, in the saline conditions plant growth promoting rhizobacteria could be used to directly increase plant growth and yield by plant promoting mechanisms and indirectly increase soil fertility condition and plant nutrition by increasing soil biological indices.