COMPARISON AND PRELIMINARY CHARACTERIZATION OF SIDEROPHORES PRODUCING FLUORESCENT PSEUDOMONADS DIVERSITY IN REPLANT PROBLEM AND NORMAL SITES OF APPLE AND PEAR
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2010
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ABSTRACT The present study attempted to identify and characterize fluorescent Pseudomonas species isolated from rhizosphere of apple and pear growing in normal and replant sites of Chamba distt.. and to optimize and maximize its siderophore production, its purification and in vitro antagonistic action against phytopathogens. All Pseudomonas isolates showed additional features like production of antifungal metabolites, hydrogen cyanide, indole-3-acetic acid, protease enzyme and phosphate solubilization. Four Pseudomonas isolates (PN 3 BAK, PR 5 BAK, AN 4 BAK and AR 5 BAK) were selected for further production purpose after screening for siderophore activity. Siderophore production was optimum at temperature 300C, 72 h of incubation period, shake condition (90 rpm) and pH 7 in an iron free succinate media. An attempt was also made to purify and partially characterize siderophores produced by the four Pseudomonas isolates. Extraction by diethyl ether proved to be the best, giving only one peak with Dowex-50 column. The purified siderophores gave yellow spots with chrome azurol-S reagent in thin layer chromatography. Chemical characterization and spectrophotochemical detection of siderophore revealed that the type of siderophore was hydroxamate. Extracts from best selected Pseudomonas isolates showed positive antimicrobial activity against some fungal pathogens, viz., Sclerotinia sclerotiorum, Pythium sp.and Rhizoctonia solani. These strains showed their extensive inhibition effect against Xanthomonas campestris and Bacillus sp. These in vitro antimicrobial actions of Pseudomonas isolates against phytopathogens suggest the potential of the organism to serve as a biocontrol and plant growth promoting agents that could be used and further standardized for field trials for management of replant problem of apple and pear in Himachal Pradesh.