Effect of Phosphate-Solubilizing Bacteria, Mycorrhizae and Phosphorus Sources on the Growth and Phosphorus Uptake of Pistachio Seedlings

The most common method to supply phosphorus for plants is the use of phosphate chemical fertilizers that have low efficiency, high cost and harmful environmental effects. If the availability of phosphorus can be increased by using phosphorus-soluble bacteria and mycorrhiza, the phosphorus concentration and plant growth parameters may also increase and make a major change in the phosphorus nutrition of plants. The aim of this study was to investigate the possibility of using superior strains of phosphate-solubilizing bacteria isolated from rhizosphere of pistachio trees, mycorrhiza and phosphate sources on the growth and phosphorus uptake of pistachio seedlings in greenhouse conditions. The experiment was performed as a factorial experiment in a completely randomized design with three replications in 2019. Treatments included four sources of phosphorus (control, monocalcium phosphate, tricalcium phosphate, and soil phosphate), four levels of bacteria (control, Serratia odorifera, Pseudomonas fluorescens and Pseudomonas brassicacearum) and two levels of mycorrhiza (control and mycorrhiza (Funneliformis mosseae, Rhizophagus intradices, Rhizophagus irregularis and Glomus caledonium)). Analysis of variance of the data showed significant interactions between phosphorus-soluble bacteria, phosphate sources and mycorrhiza on pistachio growth indices. All three bacterial isolates had positive effects on increasing vegetative indices. Also, mycorrhiza inoculation along with bacterial inoculation showed a significant increase of 44% in root dry weight. The highest shoot to root ratio was observed with application of soil phosphate and tricalcium phosphate which increased by 19% and 37% compared to control respectively. Inoculation of pistachio seedlings by mycorrhiza increased root, stem and leaf P concentration by 90%, 104% and 122% respectively. Therefore, phosphate-solubilizing bacteria especially Pseudomonas SP and mycorrhizal fungi played an important role in increasing the efficiency of phosphorus fertilizers and reducing fertilizer use, increasing growth and phosphorus uptake of pistachio seedlings.