کلیدواژهها
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Biofilm forming PGPR, Wheat, Drought response, Antioxidant enzymes, Harvest index, Root tissue density
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چکیده
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Plant growth promoting rhizobacteria (PGPR) can attenuate the adverse effects of water deficit on plant growth. Since
drought stress tolerance of bacteria has earlier been associated to biofilm formation, we aimed to investigate the role
of bacterial biofilm formation in their PGPR activity upon drought stress. To this end, a biofilm-forming bacterial collection
was isolated from the rhizospheres of native arid grassland plants, and characterized by their drought tolerance
and evaluated on their plant growth promoting properties. Most bacterial strains formed biofilm in vitro. Most isolates
were drought tolerant, produced auxins, showed 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity
and solubilized mineral phosphate and potassium, but at considerably different levels. Greenhouse experiments
with the most promising isolates, B1, B2 and B3, under three levels of water deficit and two wheat varieties led to an
increased relative water content and increased harvest index at both moderate and severe water deficit. However, the
bacteria did not affect these plant parameters upon regular watering. In addition, decreased hydrogen peroxide levels
and increased glutathione S-transferase activity occurred under water deficit. Based on these results, we conclude
that by improving root traits and antioxidant defensive system of wheat, arid grassland rhizospheric biofilm forming
bacilli may promote plant growth under water scarcity
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