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20131
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Subject: Microbiology × End date: 2013 × Start date: 2013 × Type: Thesis ×
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    ThesisItemOpen Access
    Effect of plant growth promoting rhizobacteria on growth, osmolytes and antioxidant status of pearl millet under drought condition
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2013-02) Pandey, Megha; Sharma, Anita
    Drought is one of the most important manifestations of abiotic stress in plants. It is a major yield limiting factor of crop plants. In this regard, plant growth promoting rhizobacteria (PGPR) have been reported to play important role. Besides developing mechanisms for their own survival under stress, bacteria also impart some degree of tolerance to plants towards abiotic stresses. In this study, nine bacterial isolates (eight Bacillus sp and one Pseudomonas) were characterized for their plant growth promoting properties and tested for plant growth promotion in different varieties of four crops (pearl millet, sorghum, guar and moth). Out of 9 bacterial isolates, two isolates: P3 (Pseudomonas fluorescens) and 14B (Bacillus cereus) showed maximum plant growth promoting traits and were found to enhance plant growth of var. CZIC923 and CZP2k9 of pearl millet, respectively. 14B was found to be an endophyte through ARDRA. In an experiment for screening the genotypic specific behavior of pearl millet, six varieties of pearl millet inoculated with two PGPRs, var. CZIC923 was most responsive followed by CZP2k9 while var. CZP9603 was least responsive for plant growth promotery action of bacteria. The effect of three soil types on the performance of two PGPRs in two varieties (CZIC923 and CZP9603) of pearl millet was checked. Results showed the maximum plant growth in Pantnagar soil followed by soil of Ujhani and Mukteshwar. However, bacterial response was significantly higher in Ujhani soil. Bacterial growth and osmolyte production was checked in nutrient medium supplemented with different concentrations of polyethylene glycol (PEG). Both the isolates could grow up to water potential of -1.0 MPa and showed PGPR properties. In comparison to 14B, P3 produced increased level of exopolysaccharide (EPS), soluble sugar and proline. Three varieties of pearl millet viz. CZIC923, CZP2k9 and CZP9603 inoculated with P3 and 14B in a pot experiment under drought condition resulted in increased level of proline, antioxidant enzymes viz. Superoxide dismutase (SOD), Ascorbate peroxidase (APX), Catalase (CAT) and Guaiacol peroxidase (GPX) activities in plants. Among three varieties of pearl millet, var. CZIC923 was most drought tolerant while var. CZP9603 was susceptible. In vitro experiment using pearl millet variety CZIC923 and CZP9603 inoculated with P3 and 14B induced plant tolerance when exposed to drought (imposed by different concentration of PEG). Variety CZIC923 was highly drought tolerant as compared to var. CZP9603 as the response was further elevated by inoculating these bacteria which induced significant changes in the specific activity of different reactive oxygen species (ROS) scavenging enzymes (SOD, APX, CAT and GPX) and enhanced proline production, chlorophyll a, b and caretenoid level, relative water content of leaf, leaf EPS and reducing leaf water loss and electrolyte leakage of inoculated plants. The overall study showed the importance of rhizospheric bacteria in combating drought stress.