Browsing by Author "Belay Zerihun"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Effects of Land use Changes on Arbuscular Mycorrhizal Fungi Abundance and Diversity in Selected Agro-ecological Zones of Ethiopia: Implications for Sustainable Agro-ecosystems
    (Addis Ababa Universty, 2015-05) Belay Zerihun; Assefa Fassil (PhD)
    Arbuscular mycorrhizal (AM) filllgi association of six li'uit plant speeics [Mallgijera illdica L. (mango), l\1usa aculllinate Colla. (banana), Carica papaya L. (papaya), Citl'llS lilllOIl Risso. (lemon), Persea alllericana Mill. (avocado), and PsidiulII guajava L. (guava)] was investigated fi'om a low land area of Showa Robi!. Perecntage root colonization, spore abundance, species richness and diversity were examined. The resuit showed that ft'uit crops fell into higher spore density group of(7.2-8.8 spores g'l of soil) and low spore density group (3.7-5.3 spores g,t of soil). Accordingly, mango (1\1aJlgtfeJ'{[ il1dica), avocado (Persea americana), banana (J\1usa aCliminate), and Icmon (Citl'lIs lilllon) were fi'om thc high density spore group; whereas, papaya (Carica papaya), and guava (PsidiulII guqiava) fell into thc low spore density group at P <0.05. The AM colonization also showed that mango and lemon have high myeorrhization (71.7%), which guava has a low mycorrhization of27.3%. A total of 32 morpho species into 12 gencra were characterized fi'om all the fruit crops. The highest AMF species richness was in mango (18 species) followed by banana (16 species) and guava (14 spccies). The species Clal'OideoglolJlus c1aroideulli and Glolllus aggregatlIIn were the dominant specics ("generalists") among the fi'uit trees . . A total of 13 AMF species were detected in only one of the tested fruit trees, out of which foUl' species were recovered li'om mango indicating that the crops arc selective to specific mycorrhizal fill1gi. Key words: Arbuscular mycorrhizal fungi (AM F); GIOIIIIIS; Root colonization; Spore abundances
  • No Thumbnail Available
    Item
    SYMbiotic and Phenotypic Diversity of Rhi';(obium leguminosarum var viceae isolates (Vkiafaba) from Northern Gondar, Ethiopia.
    (Addis Ababa University, 1998) Belay Zerihun; Assefa Fassil (PhD)
    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
  • No Thumbnail Available
    Item
    Symbiotic and Phenotypic Diversity of Rhizobium leguminosarum var viceae Isolates (Vicia faba) from Northern Gondar, Ethiopia
    (Addis Ababa Universty, 2006-05) Belay Zerihun; Assefa Fassil (PhD)
    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. Key words: Faba bean, Rhizobia, Phenotypic diversity, Symbiotic effectiveness