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Title: Evaluation of Biological Control Agents against Bacterial Wilt
Advisors: FASIL ASSEFA (Dr.)
Keywords: Ensete,Xanthomonas campestris pv. musacearum
Fungal and bacterial antagonist
Copyright: Nov-2010
Date Added: 27-Jun-2012
Abstract: The present study was designed with the objective of isolating, screening, evaluating and characterizing antagonistic isolates against bacterial wilt of ensete from rhizosphere and phyllosphere of the host. A total of 361 bacterial and 145 fungal colonies were isolated. The in vitro antagonistic test on the pathogen showed that 17 fungal isolates and 3 bacterial isolates were screened to be active against the pathogen on the appropriate media with inhibition diameters ranging from 5mm to 40 mm. This indicates that the bacterial antagonists were more effective than fungal antagonists to inhibit the test microorganism with inhibition diameters ranging from 32mm to 40mm whereas the fungal antagonists were more diverse in their effectiveness than bacterial antagonists with inhibition diameters from 5mm to 21mm. The most effective antagonistic isolates (AUFB1, AUFB2, AUFB2, AUFB11, AUFB17, AUFB15, AUbB, AUbB1 and AUbB2) were characterized and identified to their genus level. The isolates AUbB1, AUbB3 and AUbB3 (bacteria) were identified as Pseudomonas. The fungal isolates AUFB2 and AUFB11 were categorized into Trichoderma, isolates AUFB1, AUFB15 and AUFB19 were classified as Penicillium and the isolate AUFB3 was identified as Verticillium. These isolates were further tested for antagonistic and plant growth promoting properties. It has been found that two bacterial isolates AUFB1, AUFB2 produced indole acetic acid, protease and solubilize inorganic phosphate whereas the isolate AUbB3 (bacterium) produced hydrogen cyanide, indole acetic acid and solubilize inorganic phosphate. It was also recorded that two fungal isolates AUFB15 and AUFB11 produced HCN and protease but the isolate AUFB15 was also produced indole acetic acid and solublize inorganic phosphate. In vivo under green house condition four effective isolates AUbB3, AUbB1, AUbB2 (bacteria) and AUFB11 (fungus) were evaluated for their efficacy against the pathogen. The data showed that the isolates AUbB1, AUbB3, AUbB2 and AUbB11 reduced the disease severity of ensete wilt with DSR (disease severity reduction) 74.8, 62.4, 57.4, and 56.4%, respectively. The isolate AUbB1 (bacterium) showed highest DSR whereas the isolate AUbB11 (fungus) showed least DSR. The isolates which showed significance pathogen reduction in vitro test and under green house conditions should be checked under field trials to further confirm their efficacy and to use them as antagonists. The result will serve as base line data for future endeavor of utilizing biological control system of ensete to increase productivity into low-input agriculture of the region and the country at large
Description: A thesis submitted to the School of Graduate Studies of Addis Ababa University in partial fulfillment of the requirements for the degree of Master of Science in Applied Microbiology
URI: http://hdl.handle.net/123456789/3216
Appears in:Thesis - Biology

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