ISOLATION AND CHARACTERIZATION OF ANTAGONISTIC BACTERIA FROM THE RHIZOSPHERE OF CHICKPEA (Cicer arietinum L.)

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Date
2021-08-26
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COLLEGE OF AGRICULTURE, UMMEDGANJ, KOTA
Abstract
Chickpea (Cicer arietinum L.) is the world’s third most important pulse crop after dry beans (Phaseolus vulgaris) and dry peas (Pisum sativum L.). India is the world’s leading producer of chickpea. Chickpea, a major crop of Hadoti region is suffered with many soil borne plant pathogens including Fusarium oxysporum f.sp. ciceri and Macrophomina phaseolina which causes wilt and dry root rot respectively. Biological control provides a low-cost, environmentally acceptable alternative to the use of expensive and damaging pesticides by reducing the activity of plant diseases. Rhizobacteria are among the one of the plant growth promoters and antagonistic organisms against soil borne pathogens. They dominate the rhizosphere and has a number of properties that have made them a popular biocontrol agent. The mechanisms by which these bacteria affect the plant growth include rhizosphere colonization, antibiosis, phosphate solubilization, iron chelation by siderophore production and induced systemic resistance. In present investigation, samples of rhizospheric soils and roots were collected from chickpea growing fields at Agricultural Research Station and College of Agriculture, Ummedganj, Kota. A total of 10 isolates were obtained from different soil samples collected before and after flowering from different investigation sites. Isolation of rhizobacteria was done on nutrient agar. Rhizobacterial isolates were designated as PR 1 to PR 10 and distinguished on the basis of morphological and biochemical characterization. On nutrient agar medium, in visible light, isolates PR 2 and PR 3 showed yellow pigment, PR 5 showed light yellow pigment and the rest of the isolates showed white pigment after 3 days of incubation. PR 3 and PR 4 showed fluorescence under U.V. light at 365nm while others were non fluorescent.The results of biochemical tests performed revealed that all the isolates showed similar results with regard to gram staining (negative), catalase test (positive), H2S test (positive) and KOH test (positive). PR 1, PR 2, PR 5, PR 7, PR 8, PR 9 and PR 10 showed positive results in starch hydrolysis test. Out of 10 isolates, 7 isolates showed positive results for casein hydrolysis, 6 isolates showed positive results for indole production and only 2 isolates PR 6 and PR 7 showed positive results for urease test. Antagonistic ability of rhizobacterial isolates was evaluated under laboratory conditions through dual culture method against F. oxysporum f. sp. ciceri and M. phaseolina. Mycelial growth inhibition of Fusarium oxysporum f. sp. ciceri was found maximum against PR 3 (55.22%) followed by PR 2 (16.33%). The inhibition of M. phaseolina by the rhizobacteria was found lower than that from F. oxysporum, but maximum growth inhibition was found when PR 3 (16.44%) was used as an antagonist. PR 3 was further characterized for the purpose of identification. PR 3 showed round colony with an entire/regular margin and a slightly raised elevation. The colony was smooth and transparent, with yellow pigmentation that fluoresces under U.V. light and showed negative gram staining reaction. The isolate was found to be a highly motile on SIM medium, microscopic observations revealed short rod-shaped bacteriumoccurring in single cell arrangement. Biochemical tests revealed that rhizobacterial isolate PR 3 showing antagonism against F. oxysporum f. sp. ciceri, was positive for catalase and oxidase tests, and negative for starch hydrolysis, and may thus be identified as a strain of Pseudomonas fluorescens.
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ISOLATION AND CHARACTERIZATION OF ANTAGONISTIC BACTERIA FROM THE RHIZOSPHERE OF CHICKPEA (Cicer arietinum L.).
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