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Title: Characterization of Bacterial Wilt Pathogen (Ralstonia Solanacearum L.) of Ginger (Zingiber Officinale Roscoe) and Its Controls Using Trichoderma and Pseudomonas Isolates
???metadata.dc.contributor.*???: Dr. Tesfaye Alemu
Ibrahim, Abdella
Keywords: Bacterial Wilt;Biocontrol;Biovar;Ralstonia solanacearum;Race 4
Issue Date: Apr-2017
Publisher: Addis Ababa University
Abstract: Ralstonia solanacearum (Rs) race 4 causes bacterial wilt of edible ginger (Zingiber officinale) and limits the crop production in the tropics. The present study was undertaken to isolate and characterize ginger bacterial wilt agent (Ralstonia solanacearum) and to evaluate inhibition of Ralstonia solanacearum by Trichoderma and Pseudomonas isolates in a green house and laboratory experiments in 2014/15 season. Totally, 10 isolates of Trichoderma and 10 isolates of Fluorescent pseudomonas were isolated and characterized. Inhibitory effect of the biocontrol agents was evaluated in vitro following agar well diffusion method for their efficacy against Ralstonia solanacearum. The experimental design was complete randomized design (CRD) with three replications. Data on yield and quality parameters, disease reactions, biocontrol efficacy had been collected and analysed. Based on the result of In vitro inhibition test only four isolates that inhibit the growth of the pathogen were selected and used under the green house experiment. In vitro antagonistic activities of Pseudomonas fluorescens1 and Pseudomonas fluorescens2 showed the maximum inhibition of Ralstonia solanacearum with an inhibition zone of 30 and 39.5 mm respectively. Among antagonists tested P. fluorescens, were found to be more effective in the reduction of disease severity and also increased the biocontrol efficiency when compared to untreated control by 44.4 and 92%, respectively. Also, application of antagonists significantly increased plant yield by 1.6 ton/h. ANOVA showed that a wisely designed combined treatment was found to be more effective than single treatment application. Overall, the result showed that the selected antagonistic isolates managed to suppress the disease caused by the pathogen, R. solanacearum effectively. Thus, it can be concluded that the incidence and severity of bacterial wilt of ginger disease can significantly be reduced by the combined use of antagonists in an equal suspension with foliar spray in order to have a higher yield and with minimum health risk as well as environmental pollution. Cultural characteristics of isolates on Tetrazolium Chloride (TZC) Agar selective medium showed light to red color with the characteristic red center which resembles the pathogen Ralstonia solanascearum. Biochemical and physiological characteristic revealed that similarities among isolates and strains were grouped in biovar III and corresponds to race 4 of the pathogen. Hence, further study is necessary to check the ability of the anatagonists to control the disease under field conditions
Description: 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 (M.Sc) in Applied Microbiology
Appears in Collections:Thesis- Microbial, Cellular and Molecular Biology

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