SYMbiotic and Phenotypic Diversity of Rhi';(obium leguminosarum var viceae isolates (Vkiafaba) from Northern Gondar, Ethiopia.

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Addis Ababa University


Twenty-one strains of RhizobiulIl ieglllllinosarlllll val'. viceae spp (Vicia laba) 11'0111 21 sites/of North GondaI' were isolated 11'0111 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 RhizobiulIl ieglllllinosarlllll val' viceae, except AUFR13. Almost all of the isolates grew between 15°C and 35°C and failed to grow at 40°C, except AUFR22 and AUFR28. All isolates failed to grow at 1 % NaCI, except AUFR12 and AUFR28. AUFRI8 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 RhizobiulIl ieglllllinosarlllll val'. viceae, so that 95% of the tested isolate were resist elylhromycin 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 dlY 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 AUFRI4, AUFRI5, AUFR24, 1-0