Studies on isolation, identification, characterization and evaluation of potential rhizobacterial isolates against Rhizoctonia solani Kühn of soybean
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Date
2020-11
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
A total of thirty-one rhizobacterial isolates obtained from maize and soybean rhizospheric soil samples from various location of Pantnagar on two different media Kings B and Nutrient agar media were culturally identified and evaluated for their antagonistic potential against Rhizoctonia solani of soybean. The cultural characteristics included colony colour, shape, size, margin, surface and elevation. Seven isolates which inhibited growth of Rhizoctonia solani with highest being recorded with isolate MR3 (82.05%) followed by SR1 (68.28%), SRP3 (59.82%) , SRP4 (51.28%) , SRP1 (49.56%) , SR2 (48.72%) and SRP2 (40.18%) were morphologically, biochemically and functionally characterized. The morphological test clearly revealed that only two were gram positive and rest were gram negative. Biochemical test includes Catalse test, Oxidase test, Urease test, Starch hydrolysis test, Gelatin liquefaction, Cellulase test, Methyl red test and Citrate utilization test. On the basis of morphological and biochemical characterization it can be presumed that isolates SR1 and MR3 were related and other isolates SRP2, SR2, SRP3, SRP1 and SRP4 were more related. Screening for their functionality showed that 6 of the isolates produced nitrogen fixation, 3 exhibited phosphorus solubilization with SRP 4 showing highest solubilization index (2.50), 6 potassium solubilization with SRP 3 showing highest solubilization index (2.91), 3 exhibited siderophore production, 2 known for IAA production and 6 showed Ammonia production property. On the basis of functional and antagonistic evaluation four isolates were selected SR1, SRP3, SRP4 and MR3. The compatibility among the rhizobacterial isolates and with Trichoderma isolates (PT-6, PT-10, DDNT-4) were screened. Isolate SRP4 was compatible with all other isolates and isolate SRP3 was compatible with all Trichoderma isolates. Bacterization with potential isolates offered protection against aerial blight under controlled glass house condition with maximum growth inhibition by SRP 4 (55.00%). The potential isolates were further evaluated for their growth promotion activity and induction of defence related enzymes. The results obtained indicated that isolate SRP 4 bacterized plant showed highest shoot length (43.65 cm), root length (10.57 cm), fresh shoot weight (2.20 g) and fresh root weight (0.34 g) and chlorophyll content ( chl a-1.91mg/g FW, chl b-0.94 mg/g FW, total chl-2.85mg/g FW). Treatments that were bacterized and challenged with pathogen showed higher accumulation of POD (132.24 nmol/min/mg protein), SOD (10.27 unit/mg protein/min), Chitinase (140.56 μg glucose/min/mg protein) and β-1,3-glucanase (320.63 μg glucose/min/mg protein) as compared to only bacterized plants. While the absolute control depicted the lowest accumulation of PR proteins. Treatment SRP4 showed highest production of protein, Chitinase, β-1,3-Glucanase, POD and SOD. Overall isolate SRP4 is one such isolate that proved outstanding for suppressing aerial blight of soybean and having PGP traits also.