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Title: Symbiotic Properties of Rhizobium from Crotalaria Ocroleuca Used for Intercropping in Coffee Plantations in South-West Ethiopia
???metadata.dc.contributor.*???: Dr. Fasil Assefa
Jarra, Animaw
Keywords: Cultural Characters;Gambella;Ph Tolerance;Symbiotic Effectiveness;IAR
Issue Date: Aug-2017
Publisher: Addis Ababa University
Abstract: It has been established that the symbiosis between Rhizobium and legumes are a cheaper and usually more effective agronomic practice for ensuring an adequate supply of nitrogen for legume based crop and pasture production than the application of nitrogen fertilizer. Crolotalaria ocroleuca is one of the members of crotalaria grown as cover crop or inter crop in southern and south western parts of Ethiopia. Nineteen isolates were isolated from the root nodules of Crolotalaria ocroleuca from coffee growing area in Godere Wereda, Gambella region under Teppi Coffee plantation Enterprise. Presumptive tests and microscopic features confirmed that the isolates were rod shaped and gram-negative rhizobia. Based on colony and growth characters the isolates were grouped into two groups. Accordingly, 15 isolates were fast growing and acid producing Rhizobium spp; whereas four isolates (AAUCR4.AAUCR9, AAUCR14 and AAUCR18) were slow growing and alkali producing Brady rhizobium spp. Most of the isolates utilized the carbohydrates; sorbitol, xylose, and lactose, whereas only 26% and 15% were able to utilize starch and Na-citrate, respectively. All isolates were resistant to kanamycin and erythromycin at lower concentration of 2.5 and 5 μm/ml. Only 68% and 79% were résistance at (2.5 μm/ml) and 63% and 16% of the isolates were resistant at (5 μm/ml) to neomycin and gentamycin, respectively whereas isolates (AAUCR9 and AAUCR18) were resistant to all the tested antibiotics. The isolates also showed variability in their physiological characteristics. All isolates grew at 300C .while, 63% and 53% of the isolates were able to tolerate 150C and 400C respectively. All isolates were able to grow at lower salt concentration (1-2%), and five isolates (26%) showed tolerance up to 4%. Only isolate (AAUCR9) was considered highly osmo-tolerant since it grew at 5% of salt concentration. Amongst the isolates, 21% were able to form clear zones around their colonies on Pikovaskaya’s medium and hence, they were considered as phosphate solubilisers with solubilisation index ranging from (2.2 -3). Relative effectiveness of the isolates was calculated by dry mass of the inoculated plant over the dry mass of positive control has significant difference within and among the treatment and positive and negative control at (p<0.05 Tukey’s test HSD) and accordingly, 47%, and 32%, of the isolates (79%) were highly effective (80-100%), and effective (50-80%) in nitrogen fixation. Generally, with over all competency analysis measurement two isolates AAUCR9 and AAUCR18 were the best isolates in terms of effective nitrogen fixation and tolerance to various ecological features that could make them competent against prospective candidates under field conditions.
Description: The Thesis is summited to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requiremnt for the Degree of Master of Science in Applied Micro Biology
Appears in Collections:Thesis- Microbial, Cellular and Molecular Biology

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