ISOLATION AND CHARACTERIZATION OF PLANT GROWTH PROMOTING RHIZOBACTERIA (FLUORESCENT PSEUDOMONADS) FROM ERBIL SOIL, KURDISTAN REGION-IRAQ AND USE TO IMPROVE GROWTH AND YIELD OF ZEA MAYS
Plant growth promoting rhizobacteria (PGPR) are a group of bacteria which can enhance growth parameters and yield of host plants and can be used as biofertilizers. Fluorescent pseudomonads are considered to be one of the most promising groups of plant growth promoting rhizobacteria involved in promoting of plant growth. The current study was aimed to isolate and identify plant growth promoting fluorescent pseudomonads from Erbil soil, and evaluate the plant growth promoting bioagents of the isolated strains then selection the most efficient isolates and use to improve Zea mays growth and yield. For this purpose, random sampling from the rhizosphere area was performed. Fluorescent Pseudomonads were isolated by culturing in enriched and selective King B medium and were identified based on morphological and biochemical assays. A total of 14 strains of fluorescent Pseudomonads were isolated and 8 isolates identified as Pseudomonas fluorescens and 6 isolates belonged to Pseudomonas putida. Plant growth promoting traits of the isolates were also studied such as phosphate solubilizing activity, IAA, siderophore, and HCN production. All isolates exhibited high potential of phosphate solubilisation, IAA, HCN and siderophore production, except (Ppu9) isolate and (Pfl6, Pfl12, and Ppu13) isolates showed negative results in HCN and siderophore production, respectively. The most efficient isolates (Pfl3, Pfl10, Ppu8, and Ppu11) were selected for pot experiment and used to inoculate Zea mays seeds before sowing. After harvesting, data were collected on shoot and root length, shoot and root dry weight, number of grain per cob, grain yield per plant and grain yield per hectare. Results showed that all isolates had significantly (p ≤ 0.05) increased crop growth and productivity. The highest growth and yield were founded in combined inoculated plants with Pfl3+Ppu8 followed by Pfl3+Ppu11treated plants, which increased significantly over than single inoculated and non-inoculated plants. The results revealed that plant growth promoting fluorescent pseudomonads can be used as biofertilizer to improve plant growth.
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