Biotechnology

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Browsing Biotechnology 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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    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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    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.