Isolation, Characterization and Selection of Efficient Fluorescent Pseudomonads Against Sclerotium rolfsii and Colletotrichum truncatum of Soybean
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Date
2017-10
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University of Agricultural Science, Dharwad
Abstract
A study was made to isolate, characterize and select efficient fluorescent pseudomonads against Sclerotium rolfsii and Colletotricum truncatum in soybean, in the Department of Agricultural Microbiology, University of Agricultural Science, Dharwad. Sixty two fluorescent pseudomonads were isolated from 37 rhizosphere soil sample of soybean collected from Belagavi and Dharwad districts of Karnataka, during 2016. These isolates were subjected for their morphological, biochemical, physiological and functional characterization.
All the isolates were gram negative rods, exhibiting light green, green, dark green and light orange coloured colonies under UV light. Fifty native fluorescent pseudomonads were tentatively identified as Pseudomonas fluorescens, 10 as P. aeruginosa and 2 isolates as P. aureofaciens strains based on Bergey’s manual of Determinative Bacteriology. With respect to functional characterization, fifty two isolates were positive for P- solubilization. Forty seven isolates were positive for hydrogen cyanide (HCN) production, among which 10 of the isolates were strong HCN producers. All the isolates were positive for siderophore production (6.00 to 36.37 mm). Whereas, indole acetic acid (IAA) and gibberlic acid (GA) production ranged from 39 to 28.03 and 0.5 to 18.52 g/25 ml of broth, respectively. Out of 62 isolates, 51 and 38 were inhibitory to S. rolfsii and C. truncatum respectively in dual plate technique. Seven potential isolates were selected for pot culture evaluation against both the pathogens.
Under pot culture experiment, out of seven isolates, DFP48 exhibited highest plant growth promotional activity with least disease incidence of 13.09, 19.89, and 21.96 per cent at 15, 30 and 60 DAS respectively against S. rolfsii top soil challenge inoculated with 5 per cent of S. rolfsii. Similarly DFP54 showed maximum plant growth promotional activity and recorded least anthracnose disease incidence of 11.90 and 13.87 at 30 and 60 DAS respectively, against Colletotricum truncatum foliar spray inoculated with 105 CFU/ml (Colony Forming Unit).