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چکیده
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Soil salinity is among the most significant environmental stresses in agriculture, suppressing plant growth and productivity of crops worldwide. Under high salinity conditions, plant growth and photosynthesis are adversely affected due to the increased amount of ethylene in root, ionic imbalance and hyper-osmotic condition in plants. Treatment of plant seeds and seedlings with plant growth-promoting rhizobacteria (PGPR) is a new approach that has been developed in recent years to alleviate the adverse effects of salinity. PGPR containing ACC deaminase enzyme reduce the level of stress ethylene and stimulate plant growth under various biotic and abiotic stress conditions. The present study aims at characterizing Pseudomonas fluorescens strains (B10, B1-10, B1-11 and B4-6) isolated from the rhizosphere of barley plants and evaluating the influence of potent PGPR isolates on growth and yield of five barley cultivars (Desert, Mid-day, Zehak, South and Karun) under salinity stress. The bacterial strains were evaluated for salt-tolerance, production of ACC-deaminase, and plant growth promoting activity under in vitro conditions. Thereafter, plant growth and yield in barley cultivars following inoculation with salt-tolerant, ACC deaminase producing PGPR strains under salt stress were quantified under greenhouse condition. Results indicated all bacterial strains were salt-tolerant (1-8% NaCl), able to solubilize phosphate and produce siderophore, indole-3-acetic acid (IAA) and ACC-deaminase. It was also revealed that under various levels of salinity (50, 100 and 150 mM NaCl) inoculation with PGPRs had positive impacts on growth parameters and yield of barley cultivars including plant height, spike length, weight and number, peduncle length, number of grains per spike, 1000-grain weight and grain yield, comparing to uninoculated control. Inoculation of barley cultivars with bacteria ameliorated the negative effects of salinity and resulted in increase in growth and yield. Be
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