Abstract
Information on microbial production of cytokinins and their effect on plant growth are limited. Therefore, the objective of the present study was to investigate cytokinins production by Pseudomonas sp., a major component of rhizobacteria with multiform and diverse activities, which enhance plant growth by synthesizing various secondary metabolites. In the present investigations, thirty Pseudomonas isolates were isolated from the rhizosphere of Pyrus and Malus and were screened for cytokinins production (50 to 210 μg/ml). Four strains viz PN-4-SAN, PN-10-SAN, AN-2-NAG and AN-4-NAG were selected on the basis of their higher cytokinins production. The maximum cytokinins production was observed at 72h incubation period in nutrient broth at pH 7.0 under shaken condition at 28°C. Cytokinins were extracted, purified and evaluated by thin layer chromatography and specific bioassay method. Key words: Cytokinins, plant growth promoting rhizobacteria (PGPR), Pseudomonas sp., thin layer chromatography, radish cotyledon bioassay.
Highlights
Fluorescent Pseudomonas species have emerged as largest and potentially most promising group of plant growth promoting rhizobacteria (PGPR)
Phytostimulatory effect of PGPR may be initiated by several ways but the production of phytohormone such as cytokinins and facilitating resource acquisition by such bacteria is direct mechanism of plant growth promotion (Garcia de Salamone et al, 2001; Glick, 2012; Ramadan et al, 2016) while indirect mechanism of action may involve antibiotic production, depletion of iron from the rhizosphere, synthesis of antifungal metabolites, production of fungal cell wall lysing enzymes, competition for sites on roots and induced systemic resistance (Glick, 2012)
The rhizospheric soil samples were evaluated for the status of total bacterial population viz a viz Pseudomans sp
Summary
Fluorescent Pseudomonas species have emerged as largest and potentially most promising group of plant growth promoting rhizobacteria (PGPR). Cytokinins have key regulatory roles in plant growth and development They promote seed germination, de novo bud formation, release of buds from apical dominance, stimulation of leaf expansion and of reproductive development besides on, retardation of senescence (Mok, 1994). Some of these effects have been observed in cucumber cotyledon when inoculated with Pseudomonas aeruginosa E2 (Hussain and Husnain, 2009)
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