Identification of Indolic Compounds Produced by Selected Strains of Fluorescent Pseudomonads and Their Inoculation Effect on Growth of Canola

Plant growth promoting rhizobacteria (PGPR) are considered to promote plant growth using one or more mechanisms. Pseudomonas bacteria، specially P. fluorescens and P. putida، are the most important kinds of PGPR. Production of auxin by PGPR is one of the main mechanisms that could promote growth and yield of plants. In this research، fifty strains of Fluorescent Pseudomonads selected from microbial culture collection of Soil and Water Research Institute were used. The ability of the strains for production of auxin compounds were evaluated by high performance liquid chromatography (HPLC). Results indicated that 36 isolates (72%) were able to produce at least one type of indolic auxin compounds including indole-3-acetic acid (IAA)، indole-3-acetamid (IAM)، and indole-3-lactic acid (ILM). None of the strains produced indole-3-butyric acid (IBA). A greenhouse experiment was conducted to evaluate the effects of inoculating canola seeds with IAA-producing strains on canola growth. The results showed that the strains significantly increased the height of the aerial parts (up to 15. 5%)، shoot dry weight (up to 58%) and root dry weight (up to 305%). Also vivid differences were seen in morphology and density of root hairs of plants inoculated by the strains. Hence، the studied strains have positive effects on canola plant growth indices through producing IAA.