Effects of Plant Growth Promoting Bacteria and Irrigation Levels on Physiological Traits and Yield of Flax (Linum usitatissimum L.)

To evaluate the effects of plant growth promoting bacteria and irrigation levels on some physiological traits and yield of flax, a split-plot experiment was conducted based on randomized complete block design with three replications at the research farm of Agricultural Faculty of Shahrekord University in 2015. The main factor was three irrigation levels (100 % of full irrigation as control, 75 and 50 % of full irrigation) and the sub-factor was seven levels of plant growth promoting bacteria (no inoculation as control and inoculation with Bacillus</em> SP.</em> strain1, Bacillus</em> SP.</em> strain2, Bacillus amyloliquefaciens</em>, Azotobacter Chroococcum</em>, Pseudomonas putida </em>and Azospirillium lipoferum</em>). The interaction effect of irrigation and bacterial inoculation on relative water content, cell membrane stability, chlorophyll a, b and carotenoid content, chlorophyll a/b ratio, water use efficiency, number of capsules per plant, 1000 grain weight and seed yield were significant but non significant on seed number per capsule. The highest amounts of measured traits in each irrigation level were related to the bacterial treatments. The highest seed yield (with 62% increase) was obtained from Bacillus</em> sp. strain1 in treatment and 100% of full irrigation as compared to that of control. According to the results of main effect of irrigation on number of seeds per capsule, full irrigation treatment resulted in highest number of grain per capsule as compared to the other levels. Among bacterial treatments, B</em>. Amyloliquefaciens </em>had the highest significant number of seeds per capsule, as compared with no inoculation treatment. The effects of treatments of Bacillus</em> SP.</em> strain1, B</em>. amyloliquefaciens </em>and A. Chroococcum</em> treatments were more pronounced as compared to other bacterial treatments traits studied under normal and stress conditions. According to the results of this research, flax seed treatment with plant growth promoting bacteria is recommended flax seed production under water deficit conditions.