Browsing by Author "Alemu Tesfaye (PhD)"

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    Diversity of Onion Basal Rot (Fusarium Isolates) and Their Management Using Bacillus Isolates Under Laboratory and Glasshouse Conditions
    (Addis Ababa University, 2015-10) Chebte Abreham; Alemu Tesfaye (PhD)
    In Ethiopia onion has an immense economic, nutritional and medicinal value among all vegetables. The crop is also proved to be income generating for smallholder farmers of east Shewa. However, basal rot disease has put a major hindrance for the productivity of onion in the area. Therefore, This study was conducted to isolate and characterizes Fusarium isolates of onion and to evaluate the antagonism effects of Bacillus isolates to control the disease. For isolation of Fusarium species a total of 43 diseased plant samples were collected randomly from three onion growing districts of east Shewa Zone. Biocontrol agents were isolated from the rhizosphere soil of onion. According to morphological characters, all isolates were identified as Fusarium oxysporum, Fusarium solani and Fusarium proliferatum. Pathogenicity of the isolates were tested under in vitro and glasshouse conditions. Rot lengths measured on cross section of onion bulbs caused by Fusrium isolates ranged from 0.23 cm (AAUFI2 and AAUFI6 each) to 2.1 cm (AAUFI16). The shortest root length (22.6 mm) was produced by isolates AAUFI16 while the shortest shoot length (138 mm) and the smallest dry weight (0.5 g) were produced by isolate AAUFI2. Percentage incidence of the isolates ranged 58.3% to 100%. Bacillus isolates were effective against Fusarium isolates. In vitro mycelial growth inhibition percentage by Bacillus isolate ranged from 53.6% (in AAUFI20) to 72.3% (in AAUFI4). Incidence of basal rot disease was significantly reduced by up to 41.5% (average) after treated with Bacillus isolate while root length, shoot length and dry weight increased significantly compared to the positive control. Percentage of disease control by isolate AAUBI3 ranged 33.3% to 66.67%. Based on the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) restriction fragment length polymorphism (RFLP) analysis, ten Fusarium isolates were divided into two major groups with similarity coefficient ranged from 0.38 to 1.0. Effects of basal rot disease on onion crop can be reduced by using this bioagents with other control methods. Keywords: Allium cepa L., Antagonism, Bacillus, Fusarium, Genetic diversity, athogenicity
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    Effect of Variety Tolerance, Soil Amendment and Biological Control Agents in the Management of Bacterial Wilt (Ralstonia Solanacearum) of Potato (Solanum Tuberosum L.) Under Field Condition in Chencha, Southern Ethiopia
    (Addis Ababa University, 2019-06-06) Solomon Atsede; Bekele Tamrat (PhD); Alemu Tesfaye (PhD)
    Potato (solanum tuberosum L.) is an important food security crop which provides higher carbohydrate per unit area within a short period of time than the major cereals wheat and reice. Its production in Ethiopia is increasing rapidly, as it is grown by more than a million small holder farmers as a food and a cash crop. However, potato yield is low due to many factors among which diseases and insect pests are among the most limiting factors to the production of potato. Bacterial wilt caused by Ralstonia solanacearum is the second most important disease next to late blight. The pathogen is soil born and transmitted by seed, irrigation water and contaminated tools making its management a complex issue that require an integrated approach. Three separate experiments were carried out during 2015 and 2016 short rainy seasons under natural infestation condition on farmers’ fields at Chencha, Southern Ethiopia. The aim of the first experiment was to screen bacterial wilt tolerant potato genotypes and better yield. In the second experiment, soil amendments compost and manure at the rate of 20 t/ha, lime, and recommended fertilizer (110 kg of N/ha and 96 kg of P2O5/ha) and their combinations were studied to identify effective soil amendments which reduce the effect of the disease, improve yield and the soil condition. Thirdly, different biocontrol agents which were found effective in previous laboratory and greenhouse studies were tested for their efficacy on the disease development and improvement of yield. All experiments were laid in RCBD with four replications. Data on disease, yield and yield components were collected and subjected to analysis using SAS 9.3 and minitab softwares. The response of potato genotypes to the wilt disease varied significantly (p < 0.05) under natural infestation condition. The genotypes Cruza, Shangai, and CIP clone CIP-392661.18 showed lower DSI and AUDPC combined with a higher marketable yield. The local variety Sula also showed a better performance in terms of disease tolerance and yield which calls for further molecular study. Soil amendements showed better disease control than the control treatment though there was no significant differences between the organic fertilization and their iv combinations except for lime only treatment. The biological control agents also generally improved crop performance and delayed the onset of the disease. Treatments also significantly differed in terms of DSI, AUDPC and tuber yield. The lowest AUDPC value (738) and highest tuber yield (34.8 t ha-1) was obtained from Neem gold @ 0.25 ton ha-1. However, Neem gold @ 0.1 ton ha-1 showed the highest AUDPC (1565) followed by arbuscular mycorrhizal fungui (AMF) and control, which achieved intermediate and the lowest AUDPC (1545 and 1500, respectively). The lowest yield (28 t ha-1) and the highest percentage of infected tubers (25.3 %) was recorded from the control plot. From these results, it can be recommended that the use of an integrated approach including tolerant varieties, application of soil amendment and biocontrol agents can improve potato productivity and lower the effect of bacterial wilt in the study area although in the presence of pathogen in the soil. This approach can be recommended as a better alternative to current practices as it is user-friendly and environmentally safe. However, the availability and cost of biocontrol agents and soil amendments should be taken in to consideration when making recommendations outside the study area.
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    Evaluation of Rhizobacteria and Trichoderma Isolates From the Rhizosphere of Faba Bean (Vicia Faba L.) for their Potential In the Management of Chocolate Spot (Botrytis Fabae Sard.) Disease and Host Plant Growth-Promoting Properties
    (Addis Ababa University, 2021-02-02) Firdu Zewdineh; Assefa Fassil (Professor); Alemu Tesfaye (PhD)
    Faba bean (Vicia faba L.) is one of the legume grains used as a source of food for human. However, the productivity of the crop is less due to chocolate spot (Botrytis fabae Sard) in Ethiopia. The disease can be managed through the applications of fungicides such as MORE 720 WP and ORZEB 80 WP. Alternatively, an eco-friendly approach is initiated using Trichoderma and bacterial species to manage the disease. Therefore, in this study, Trichoderma and bacterial species were evaluated against Botrytis fabae under in vitro and in vivo conditions. The data were analyzed by SPSS version 24. The bacterial strains inhibited B. fabae (6-68%) upon 3-9 days in the dual culture method. The highest inhibition was recorded by B. tequilensis AAUB100 that displayed 80% and Serratia nematodiphila AAUB146b with 79% inhibition at 20% (v/v) of the culture filtrate. A 200-760 μg mL-1 of solubilized phosphate was also released upon 3-6 days by the isolates. Trichoderma harzianum AAUT14 was the most effective antagonist with more than 88% of B. fabae inhibition in the dual culture upon 9 days. The isolates of Trichoderma also showed inorganic phosphate solubilization that ranged from 135-509 μg mL-1 upon 3-9 days. Under the greenhouse study conducted using a completely randomized design, the disease incidence reduced by 36-50% on Ashebeka variety compared to the control (T1) in which T. harzianum AAUT14 and B. subtilis AAUB95 (T4) displayed the highest reduction (50%) of disease incidence upon 60 days. The disease severity reduction was much pronounced upon 80 days ranging from 41-55% compared to the disease severity, which did not show significant difference (p>0.05) between T4 and T5 (MORE 720 WP) upon 60 days. A 3.8-34% of disease incidence and 15-26 disease severity reduction was also observed upon 60 days on Hachalu variety. An area under disease progress curve (AUDPC) of 405.97% and 415.33% was displayed by T5 and T6 (ORZEB 80 WP), respectively on Ashebeka variety. Similarly, 377.98% by T5 and 412.48% by T6 of AUDPC was illustrated in Hachalu variety showing no significance difference (p>0.05) with T4. Under field conditions conducted using a completely randomized block design, the combination of Trichoderma harzianum AAUT14+B.subtilis AAUB95 (T4) reduced the disease incidence and severity showing no significance difference (p>0.05) with T5 upon 70 and 90 days. Nevertheless, in Hachalu variety (Trial 2), the treatment reduced the disease incidence from 23-51% and disease severity 37-54% upon 90 days. In addition, the AUDPC ranged from 1586.1-2250.0% in trial 1 and 1382.0-2454.5% in trial 2. The grain yield was also increased by 34% and 38% in trial 1 and 2, respectively over the controls by T4. In conclusion, the mixture of T. harzianum AAUT14 and B. subtilis AAUB95 or in some cases T. harzianum AAUT14 performed best in controlling chocolate spot and growth promotion of faba bean under greenhouse and field conditions.
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    Morphological and Molecular Characterizations of wilt disease of Ginger (Zingiber officinale Roscoe) Caused by Fusarium sp
    (Addis Ababa University, 2015) Mekuria Tsegaye; Alemu Tesfaye (PhD)
    Ginger rhizome, pseudostem, leaf and soil samples were collected from ginger growing areas of southwestern Ethiopia. Fungal pathogens were isolated from ginger parts showing vascular browning symptoms and soil following standard methods. Isolation revealed fungal isolates belonging to four genera: Fusarium, Penicillium, Aspergillus andTrichoderma. Out of 24 fungal isolates 14 isolates were Fusarium species. In vitropathogenicity test resulted in pathogenicity index (PI) values ranging from 10.96% +1.55(AAUFG13) to 45.35% +11.57 (AAUFG6). Cultures of Fusarium species on PDAmedium showed white, creamy white, dull pink and pink coloration. They imparted dullwhite, orange, light reddish purple, intense reddish purple and dark reddish purple pigmentations on the riverse side. Canoe shaped macroconidia, ovoid microconidia and short phialides were pertinent to all of the Fusarium isolates. Based on their cultural and morphological characters the isolates were identified as Fusarium oxysporum. The ability of the isolates to induce rhizome rot confirmed the forma specials rank of the isolates as F. oxysporum f. sp. zingiberi (Foz). PCR- RFLP profile of the ITS1 rDNA region indicated genetic variation between the Fusarium isolates. In silco RFLP digestion of ITS1 rDNA sequences of F. oxysporum retrieved from the fungal ITSoneDB was performed using online restriction mapper software and restriction enzymes used in the actual experiment. The result of the in silco restriction digestion simulation was similar with the actual PCR_RFLP study supporting that the isolates are Fusarium oxysporum. Key words: Fusarium wilt; ITS1;Pathogenicity; PCR-RFLP; Rizhome rot
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    Reported Tuberculosis (Tb) and Tb/Hiv Co-Infection in Motta Town Health Care Facilities, Northwest Ethiopia
    (Addis Ababa University, 2017-09) Liyew Zelalem; Alemu Tesfaye (PhD)
    Tuberculosis (TB) caused by Mycobacterium tuberculosis is a major public health problem and continues to be a world leading killer disease primarily affecting the poor people in developing countries. The necessities of this study to provide information’s against TB about continuous evaluation of TB in different settings. The objective of the current study was to determine the reported TB and TB/HIV co-infection among patients attending public health care facilities found in Motta town. The study also analyzed TB/HIV co-infection, case detection rate (CDR) treatment success rate (TSR) among patients attending Directly Observed Therapy Short Course (DOTS) by comparing to national and global level. A five year (2012-2016) retrospective cross sectional study design based on secondary data of total TB patients with socio demographic information registered from TB Registry unit of the patients found in the TB center was used and the data were analyzed using SPSS version 20 software through one sample test and one way ANNOVAs. From a total of 551 TB patients 313 (56.8%) were males and 238 (43.2%) were females with male to female ratio1.3:1. Majority of the TB cases (91.1%) were within the active economically productive age groups (15-54 years). The CDR was 39% which was lower than the national (62%), regional (52%) and global (64%) showing that the study area did not met the global target of 70% by 2015. All TB patients were tested for HIV which achieved the global target by 2015. The prevalence of TB/HIV co-infection in the study area was higher (26.9%) compared to the national prevalence (11.0%) requiring more action to control TB/HIV co-infections. Generally, there was a minimal variation in trend of TB/HIV co-infection, the reported cases of TB decreased for the last five years by 11.5%(p = 0.00). However, TB remains a major health problem in Motta town and its surroundings. Strengthening TB and HIV collaborative activities to decrease the high burden of TB/HIV co-infection of Motta town, using sensitive and recent diagnostic tools to increase the case detection rate of smear positive pulmonary TB and modifying the daily available Bacillus Calmette Guerin( BCG) vaccine to make it more effective in all age groups for the future are recommended to overcome the high burden of TB and TB/HIV co-infection. Key words: Case detection rate, Directly Observed Treatment Short course, Treatment success rate, Tuberculosis, TB/HIV co-infection
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    Studies on Biological and Mechanical Management of Coffee Berry Borer [Hypothenemus Hampei (Ferrari)] Using Beauveria Bassiana and Baiting Trap on Coffee (Coffea Arabica L.)
    (Addis Ababa University, 2017-07-03) Chekol Yonas; Alemu Tesfaye (PhD)
      The entomopathogenic fungus (Beauveria bassiana) is a cosmopolitan pathogen of different insect hosts. It is used as a natural enemy to control insect pests in agricultural systems. Coffee production in Ethiopia is damaged by the coffee pest, coffee berry borer (CBB) [Hypothenemus hampei Ferrari (Coleopteran, Scolytidae). The control measure attempt or attention given to this potentially dangerous pest is almost none/very few compared with its economic importance. In the present study, soil samples were collected from three coffee growing areas in Jimma zone, Ethiopia. For each soil sample ten Galleria larvae were used as bait for trapping entomopathogenic fungus Beauveria bassiana. The total number of Galleria larvae positive for Beauveria spp. from the different soil samples were 159 (53%) out of 300 Galleria larvae tested, in which 26.7%, 18.7% and 7.7% were from Beletechaka, Geruke and Choche farms, respectively. The three localities significantly varied in the rapped B. bassiana isolated at (P < 0.05).The amplification of the ITS region of Beauveria spp. isolates produced single fragments of about 560 bp for all tested. Further, eight randomly selected and sequenced isolates revealed 98-100% sequence similarity and shared an overall intra-sequence similarity value of 99% among our isolates. The ML analysis of the ITS region of B. bassiana formed a highly supported clade together with other isolates retrieved from GenBank. The highest evolutionary divergence estimate between sequences of Ethiopian isolates was 1%. The molecular analysis hence supported species identification based on cultural and morphological traits and confirmed the isolates as B. bassiana. Thirteen B. bassiana isolates were selected and screened for the biocontrol agent against coffee berry borer. Four parameters (percentage of spore germination, insect mortality (%), and average survival time (LT50), and spore production on the dead insect) were used for screening. Only three isolates scored > 93% spore germination, all isolates showed 100% mortality, six isolates showed shorter time of LT50 mortality approximately ≤ 84 hrs (3.5) days and four isolates produced more than 1x107 average mean spore production per beetle. Isolates varied in their ability to produce spores (F = 25.525, df = 12, P = 0.000) and for the spores to germinate (df = 12, F = 2.734, P = 0.016). Three isolates B7A, G2A and C3C merited for conidial mass production on sorghum using diphasic liquid-solid fermentation. The maximum value of mean spore concentration g-1 of spore, weight of harvested spore kg-1of substrate, spore production kg-1 of substrate and the average mean spore germination potential (%) by the 3 isolates were 4.80 x1010 , 8.26 ± 0.42, 4.01x1011 ± 2.00 x 1011 and 89.33 ± 5.01, respectively. There was a significant difference among these three isolates on spore concentration and spore production (df = 2, F= 8.208, P = 0.019) and (df = 2, F = 10.174, P = 0.012). The minimum moisture content attained within 10 days ranged between 11.09 ± 2.39 - 12.86 ± 3.75. Coffee seedlings endophytic colonization of the 13 inoculated Beauveria isolates with 1 x 108 spore/ml at 60 and 120 days of post inoculation endophytic recovery evaluation time showed progressive results from 54 (7.69%) to 90 (12.82%), from 29 (4.13%) to 51 (7.26%) and from 9 (1.28%) to 14 (1.99%) from the roots, stems and leaves, respectively. From the total of 702 inoculated subsamples, 92 (13.11%) showed endophytic recovery at 60 days and 155 (22.08%) at 120. There was no significant variation in the colonization frequency of Beauveria isolates on the coffee seedlings .The endophytic establishment of Beauveria isolates did not affect the growth of the coffee seedlings. For the control of CBB as IPM component, a total of 32 red colour baiting traps were prepared and lured with Ethanol: Methanol (E:M) mixture (1:1, 1:2 and 1:3) with releasing rate of 509.9 ± 0.06, 577.3 ± 0.02 and 580.3 ± 0.02 in mg day-1, respectively. Traps were attached to wood stakes branch in a randomized complete block design (RCBD), 12m within the raw, 15m between blocks and 1.20 m from the ground. The efficiency of the attractant (E:M) mixtures at Tepi-Baya II, Limu-Goma II () and Mizan-Aman showed no significant difference, but all were significantly (P < 0.001) different from the control. The percentage of captured CBB with E:M, (1:1, 1:2 and 1:3) at Tepi-Baya II were 427 (93%), 413 (98.6%) and 416 (95.2%) at Limu-Goma II, 97 (89%), 115 (100%) and 90 (93.8%) and at Mizan-Aman; 139 (86.7%), 122 (97.6%) and 98 (94.2%), respectively. The Non Coffee Berry Borer (NCBB) showed preferable attraction by 1:1 and 1:3 than 1:2 E:M mixture across the localities. None of the controls captured the NCBB beetles at any of the localities. The total number of NCBB captured from Tepi-Baya II, Limu-Goma II and Mizan-Aman were 1,329, 320 and 388, respectively and the trapped beetles at Tepi-Baya II were4.2 times greater in number than those captured at Limu-Goma II and 3.4 times greater than at Mizan-Aman. The outcome this research work indicated that CBB population should be checked before the pest brings a devastating effect by the application of mechanical trapping and biopesticides in combination.
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    Woody Plants Diversity, Populations Structure, Carbon Stock and Microbial Dynamics in Gara Duro Natural Forest, West Arsi Zone, Ormia, Ethiopia.
    (Addis Ababa University, 2020-07-07) Beno Kedir; Dalle Gemedo (PhD); Alemu Tesfaye (PhD); Dagafa Sileshi (PhD)
    Forest and soil carbon storage paly a sginficant role in climate change mitigation. Especial woody species are more importantly store considerable carbon. However in Gara Duro natural forest there was lackof information regarding wood species diversity, their carbon stock, under species soil carbonstock and their impacts on microbial population. This study aimed at documenting woody plants diversity, populations structre, and assessing carbon stock and effect of forest degradation on microbial dynamics in Gara Duro natural forest in Nagelle Arsi District, West Arsi Zone, Oromia, Ethiopia. A systematic sampling method was used to establish sampling plots along altitude. Woody species and soil data were collected from 47 plots of 20 m × 20 m (400 m2). All woody plant species encountered in each sample quadrats were recorded and their Diameter at Breast Height (DBH) and height were measured. The carbon stock of trees was estimated using an allometric equation. One way analysis of variance was used to test data of carbon in different pools, variations in soil microbial dynamics and soil chemical properties at P=0.05.The results showed that there were 40 woody plants in the natural forest belonging to 38 genera and 31 families. The most frequent species were Maesa lanceolata, Rubus apetalus, Croton macrostachyus, and Podocarpus falcatus. Maytenus addat, Maesa. lanceolata, Podocarphus falcatus, Croton. macrostachyus and Pittosporum viridiflorum had the highest importance value index (IVI), whereas Ficus vasta, Brucea antidysenterica, Schefflera abyssinica, Hypericum revolutum and Erica arborea were species with lowest IVI. Based on the evaluation of the diameter class, overall structure of woody species structure showed an inverted J-shaped curve.The mean carbon stock of Gara Duro natural forest was found to be 248. tons carbon ha-1, 107.20, 21.44, 2.54 and 116.04 carbon ton ha-1 were stored in the above ground, below ground, litter and as soil organic carbon, respectively. There was a significant diference between different carbon pools. The present study revealed that there was significant (p ≤ 0.05) variation in soil bacterial and fungal population of protected and nonprotected areas of Gara Duro natural forest.The soil chemical properties showed significant variation in protected and non protected areas of Gara duro forest (p ≤ 0.05). The mean pH value in protected forest was 6.57(1:2.5) while in the nonprotected forest it was 5.95 (1:2.5). Similarily, the Organic Carbon (OC) in protected forest was 1.83% and that of nonprotected forest was 1.20%. Total nitrogen (TN) content was significantly different between protected and non protected forest with 0.525% and 0.45%, respectively. Gara Duro forest was found to be important for plant and microbial biodiversity conservation, climate change mitigation and diverse ecosystem services to the local communities. Designing and implementing in-situ conservation of the forest with priority to identified plant species and promoting ecosystem services through forest management system was recommended.