Autecology and synecology of Pseudomonas fluorescens CHAO-Rif used in the cultivation of sunflower and cannabis

Plants have difficulty living in hard habitats such as heavy metal contaminated soils that the application of plant growth-promoting bacteria can be beneficial to reduce this difficulty. This study was designed to investigate the autecology and synecology of Pseudomonas fluorescens CHAO-Rif in a heavy metal contaminated soil. This research was a factorial experiment with a completely randomized design with three replications in greenhouse condition. The first factor was plant species (sunflower and hemp plants) and the second factor was soil sterilization, in which the treated soils were inoculated with Pseudomonas fluorescens CHAO-Rif bacterium purchased from the Plant Pathology Group of the Institute for Integrative Biology (IBZ) in Zurich, Switzerland. The plants were harvested at the beginning of the flowering stage. The population of the applied Pseudomonas was significantly higher (more than 1.5 times) in sterile soil planted with sunflower compared to that in unsterile soil planted with cannabis. In sterile soil, the inoculated Pseudomonas could colonize in the inner tissues of the sunflower root. Here the natural log of the number of the bacterium was 4.02±0.06, but it was not found in the cannabis root. The bacterium was found in the rhizosphere and non-rhizosphere soils and on the root surface (rhizoplane) of both plants. However, it was not found in aerial parts of the plants. In unsterile soil, the inoculated bacteria were found only in the rhizosphere and on the root surface of the plants, but not seen in the shoots and roots of the plants. Although soil native microorganisms reduced the abundance of applied Pseudomonas in unsterile soil, the application of this bacterium did not have a significant negative effect on the studied soil native microorganisms.