Browsing by Author "Chekol, Yonas"

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    Microbiological Profile of Imported and Local Brands of Canned Foods in Addis Ababa
    (Addis Ababa Universty, 2006-06) Chekol, Yonas; Ashenafi, Mogessie (Professor)
    The primary objective of this study was to evaluate the microbiological quality and safety of canned foods available to consumers on the market in Addis Ababa and also to assess the fate of contaminating pathogens in the canned foods when stored at ambient and refrigerator temperature. The distribution of drug resistance among the dominant isolates was also evaluated. A total of 100 samples of canned foods comprising 20 each of, fish, meat, vegetables, milk and soups were collected from Addis Ababa super markets and shops. Date of production, expiration and ingredients of each sample were recorded. The samples were bacteriologicall y analyzed for counts of aerobic mesophilic, Staphylococcus spp, Calif arms and yeast. The pH of each sample was determined li'om the original sample. The aerobic mesophilic bacteria were dominated by, Bacillus spp, Micrococcus spp and other Gram-positive rods. Staphylococcus spp and Coliform.l· were encountered in some fish and meat canned food products. Salmonella and Shigella spp were not detected in any of the 100 samples. A total of256 aerobic spore-forming bacilli were isolated from canned foods. B. brevis, B. cereus, B. lichell(formis, B. larvae, B. /irmus. B. macerans B. pumilus alld B subtilis were the frequent isolates. Almost all Bacillus isolates were susceptible to chloramphenicol, erythromycin, gentamycin and kanamycin. Most isolates exhibited resistance to amoxycillin and ampicillin. Of the isolates tested for antibiotic sensitivity profile 139, (53%) showed multiple antibiotic resistance. Growth of Shigella j1exilleri and Salmonella Typhimurium inoculated into commercially available canned foods (meat, fish, vegetable and soup) was shldied at refrigeration and ambient temperature. In both temperatures the strains grew and multiplied luxuriously
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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, 2017-07-04) 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.