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Title: Symbiotic and Phenotypic Diversity of Rhizobium leguminosarum var viceae Isolates (Vicia faba) from Northern Gondar, Ethiopia
Authors: Zerihun, Belay
Keywords: Faba bean
Rhizobia
Phenotypic diversity
Symbiotic effectiveness
Date Added: 4-Sep-2007
Abstract: Twenty-one strains of Rhizobium leguminosarum var. viceae spp (Vicia faba) from 21 sites of North Gondar were isolated from a range of pH 5.8-7.5 to induce nodulation on “Degaga" cultivar of faba bean. Isolates were authenticated as root nodule bacteria by their ability to form nodules on their host up on re-inoculation, except AUFR13. All of the morphological features displayed by all isolates were characteristics of fast growing Rhizobium leguminosarum var viceae, except AUFR13. Almost all of the isolates grew between 150C and 350C and failed to grow at 400C, except AUFR22 and AUFR28. All isolates failed to grow at 1% NaCl, except AUFR12 and AUFR28. AUFR18 was the only osmotolerant strain capable of growing at a concentration of 5%. The isolates also grew on a wide range of moderate acidity and alkalinity but only 10% of the isolates grew at pH5.5. With the exception of gluconate, citrate, and tartarate, almost all isolates grew on 14 out of the tested carbohydrates. The Intrinsic Antibiotic Resistance (IAR) was found to be the best of all tested physiological characters to identify the heterogeneity of Rhizobium leguminosarum var. viceae, so that 95% of the tested isolate were resist erythromycin and chloromphenicol, and 14%, 24%, 38%, 38% and 43% of the isolates tolerated streptomycin, ampicillin, rifampcin, kanamycin and naldixic acid at highest concentration, respectively. The relative effectiveness expressed as percentage of shoot dry mass of inoculants over TN control, showed that 24%, 57%, 4.7% and 9.5% of the isolates were found to be highly effective, effective, lowly effective and ineffective, respectively. The highest scores of 88-100% effectiveness of symbiotic nitrogen fixation were displayed by AUFR14, AUFR15, AUFR24, AUFR28 and AUFR32. Selected strains on soil culture were found to accumulate 81-92% on Holeta soil and 90-103% on Ambagiorgis soil of their shoot dry mass compared to their respective N-fertilized controls. All isolates were also found to increase shoot dry weight by 0- 43% higher than their respective sand cultures and response of the Holetta soil to inoculation by selected effective strains was much pronounced (47-67%) than Ambaghiorgis soil (8-25%) compared to the negative (N-) controls. The lower dry matter accumulation by Holeta soil indicates that the low pH and other soil-related factors severely affected survival, nodulation and nitrogen fixation of their indigenous rhizobia and the process can be rectified by inoculation of effective rhizobia.
Description: A Thesis Presented to the School of Graduate Studies of the Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Applied Microbiology
URI: http://hdl.handle.net/123456789/71
Appears in:Thesis - Biology

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