CHARACTERIZATION OF Bradyrhizobium japonicum AND ITS COMPATIBILITY WITH FUNGICIDES.
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Date
2019-07-23
Authors
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Publisher
Dr. Punjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra.
Abstract
Soybean [Glycine max (L.) Merrill] is cultivated intensively in India. Legumes derive 5-83 per cent of their nitrogen (N) requirement by biological nitrogen fixation under field conditions. The use of various chemicals is imperative to achieve profitable yields. However, these chemicals used as plant protectants have been found to exert either synergistic or toxic effects on legume-Rhizobium symbiosis. Therefore, present studies on ‘‘Characterization of Bradyrhizobium japonicum and its compatibility with fungicides”, were planned and conducted with defined objectives, at Plant Pathology Section, College of Agriculture, Nagpur, during 2018-19.
The test B. japonicum and Rhizobium sp. was isolated from functional root nodules of soybean plants, on congo-red yeast extract mannitol agar medium. The colonies of isolates were circular, convex, glistening, opaque and whitish pink colonies of 2-4 mm dia. with regular or entire margin with marked distinction from red colored colonies of Agrobacterium. The purified strains were aerobic, gram negative, non-spore forming and motile rods. Out of 25 purified isolates, 20 (80%) were slow grower Bradyrhizobium sp. (turn medium blue) and 5 (20%) were fast grower Rhizobium sp. (turn medium yellow) was found on YEMA media supplemented with Bromothymolblue.
The optimum growth kinetics for B. japonicum and Rhizobium sp. was 35°C at neutral pH (7.0). Both fast and slow growing rhizobia were found to be positive for oxidase, KOH, starch hydrolysis, nitrate reduction and catalase activity. Among all the 25 isolates tested, 23 isolates showed positive reaction to gelatin hydrolysis except Bj-11 and Bj-21 while, 21 isolates were reacted positive to H2S production whereas, the four isolates viz., Bj-1, Bj-2, Bj-8 and Bj-23 were negative in reaction. While all the samples were found negative for IAA production.
Pot culture experiment revealed that seed inoculation with different B. japonicum and Rhizobium sp. isolates recorded significant improvement in nodule number and plant height over uninoculated control. All the B. japonicum and Rhizobium sp. inoculants recorded higher plant height ranged from 35.00 to 65.00 cm at flowering stage. Interactions of all the inoculants ranged from 3.00 to 22.00 nodules per plant at maximum flowering period. Some of the isolates viz., Bj-9, Bj-10, Bj-14, Bj-17, Bj-19, Bj-23, Bj-25 could produce large and pink nodules indicating their effective symbiosis with soybean.
The test of compatibility with systemic, non-systemic / contact, combi-fungicides at recommended field dosages 50%, 75%, 100% and 125% of the Reommended doses were evaluated in vitro against B. japonicum of soybean, by inhibition zone technique. The fungicides carbendazim 50% WP and mancozeb 75% WP at all four dosages were found compatible with B. japonicum, as they didn’t showed any zone of inhibition, at 72 hrs of incubation. Whereas, rest of the three fungicides viz., captan 75% WP, carboxin 75% WP, vitavax power 75% WP tested at four various concentrations were found inhibited by the test bacterium and produced average inhibition zone of around 00.00-19.66 mm, 8.56mm and 10.52mm respectively, at 72 hrs of incubation.
Description
Soybean is one of the main leguminous crop of vidarbha region. So it relates to collection of soybean root nodules from different locations, isolation of Bradyrhizobium sp. and Rhizobium sp. Different physiological and biochemical tests were conducted for identification of strain. All the isolates were tested for their performance under pot culture experiment conducted in net house condition. Also, the compatibility of effective strain with different fungicides were tested against Bradyrhizobium sp.
Keywords
Glycine max, Fungicides.
Citation
DINKWAR, KU. GITANSHU TARENDRA. (2019). Characterization of Bradyrhizobium japonicum and its compatibility with fungicides. Department of plant pathology, Nagpur. Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola. M. Sc. 2019. Print. xiii, 78 p. (unpublished).