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Dr. Rasha Mohamed Mostafa El-Meihy :: Publications:

Evaluation of PGPR as Osmoprotective Agents for Squash (Cucurbita pepo L.) Growth under Drought Stress
Authors: Rasha Mohamed El-Meihy
Year: 2016
Keywords: PGPR, osmoprotectants, osmoregulators, microbial activities, drought stress, squash
Journal: Middle East Journal of Agriculture Research
Volume: 5
Issue: 4
Pages: 583-595
Publisher: Not Available
Local/International: International
Paper Link: Not Available
Full paper Rasha Mohamed Mostafa El-Meihy_squach.pdf
Supplementary materials Not Available

Evaluation of PGPR in relation with drought resistance of squash was studied in vitro and pot experiments. The activities of Azotobacter chroococcum ML1, Bacillus circulans ML2, Bacillus megaterium ML3 and Pseudomonas fluorescence ML4 as osmoprotective agents were estimated in vitro. All tested strains produced indole acetic acid (IAA) at range of (17.73-23.65 mg/ml), gibberellic acid (GA3) (9.38- 19.16 mg/ml), proline (4.69-15.06 g/ml), exopolysaccharides (21-467 g/ml), salicylic acid (25.98-28.35 mg/ml) and 1-aminocyclopropane-1-carboxylate (ACC-deaminase) (9.6-48.1 ml mole/ml/h). Furthermore, values of nitrogenase activity were 35.0 and 15.0 nmol C2H4/l/h due to using A. chroococcum ML1 and Ps. fluorescence ML4, respectively. The ability of the tested PGPR strains to enhance growth and alleviation drought stress on squash plants compared to humic acid (HA) under different irrigation levels were tested through a pot experiment. Results revealed that inoculation of squash with PGPR enhanced enzymes activities in its rhizosphere. In addition, PGPR inoculants caused significant increases in osmoregulators compounds of squash leaves and their maximum values were recorded at vegetative stage. Results also emphasized that IAA and GA3 in squash leaves were markedly increased under drought stress when plants were inoculated with PGPR strains. Whereas, abscisic acid decreased under the same conditions. Alongside, photosynthetic pigments and oxidative enzymes were strongly affected under PGPR inoculation compared to HA or chemical fertilizers applications when squash were irrigated with 75 or 50% of field capacity. Also, growth characteristics and yield under PGPR treatments were significantly higher than those resulted from additions of HA and chemical fertilizers.

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