Morpho-physiological variability and antagonistic potential of native fluorescent Pseudomonads from Zone 3A of Bihar
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Date
2017-07
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Department of Plant Pathology, BAU, Sabour
Abstract
Biocontrol agents have great demand now-a-days as they are replacing chemical pesticides to a large extent as they are cost effective and eco-friendly. The use of biological control agents as an alternative to fungicides is increasing rapidly in the present day agriculture due to the deleterious effects of chemical pesticides. Fluorescent Pseudomonads, a major constituent of rhizobacteria, encourages the plant growth through their diverse mechanisms. Its name implies, it secretes greenish fluorescent pigment called fluorescein, particularly under condition of low iron availability fluorescent Pseudomonads are one among them which not only enhance the plant growth but also control the fungal pathogens by production of antifungal metabolites.
Present investigation was focused towards isolation of fluorescent Pseudomonads from different crop rhizospheres, morpho-physiological characterization and evaluation of antagonistic potential of these isolated fluorescent Pseudomonads against three fungal pathogens viz., Rhizoctonia solani, Sclerotium rolfsii and Fusarium spp. Twenty six fluorescent Pseudomonads were isolated from different crop rhizospheric soils collected from different villages of Bhagalpur and Kishanganj. The isolates were purified on King’s-B medium and confirmed by observing under UV light. Out of twenty six, sixteen isolates were confirmed as fluorescent Pseudomonads. Among sixteen isolates twelve were found producing round to oval shaped colonies and four isolates produced irregular colonies on King’s-B agar medium. Colony colour varied from isolate to isolate viz., slightly yellowish white, green, dull white and whitish green to yellowish. Isolate WHSB produced maximum number of colonies (51.33X10-8/ml) followed by MSSB (28.33 X10-8/ml) on King’s-B medium. Colony size was found maximum (13.33mm) in MRKH followed by TMGH (12.00 mm). Fluorescent Pseudomonads produced different colour pigmentation (light green, dark green, bluish white and bluish green) at lower surface of King’s-B medium. Both the selected isolates, high fluorescent isolate (MSSB) and low fluorescent isolate (WHSB) preferred pH 7.5 for their optimum growth followed by pH 7.0 and 8.0, respectively. The same isolates also preferred the glucose as a carbon source followed by dextrose for their rapid growth.
In vitro evaluation studies indicated that isolate BMGH shown maximum antagonism against Rhizoctonia solani with 55.66 per cent inhibition of pathogen over control followed by isolate WHKH (47.16 per cent) and MSKSN (46.22 per cent). Isolate CHGH was found least effective (15.09 per cent) followed by BRKH (16.03 per cent). Against Sclerotium rolfsii, isolate LNSB had maximum antagonism (88.81 per cent) followed by WHKH (79.72 per cent) and isolate BRKH was found least effective (23.78 per cent) followed by CKSB (32.87 per cent). Isolate MZKSN and BRGH were found to have maximum antagonism against Fusarium spp. (58.74 per cent) followed by WHSB (56.65 per cent) and MRKH was found least effective (15.39 per cent) followed by MSKSN (20.29 per cent). The effective isolates screened under in vitro may further tested under field conditions and may used for management of soil-borne fungal plant diseases.
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