Browsing by Author "Mekbib, Sissay Bekele"

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    Assessment of the impacts and adaptive capacity of the Machobane farming system to climate change in Lesotho
    (African Technology Policy Studies Network, 2012) Mekbib, Sissay Bekele; Olaleye, Adesola; Mokhothu, Motlatsi N.; Tilai, Spirit B.; Wondimu, Taddesse; Johane, Masia
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    Citrus sinensis cultivation in Ethiopia and postharvest biocontrol using plant extracts and microbial antagonists
    (VDM Publishing,, 2009-01) Mekbib, Sissay Bekele
    Postharvest application of chemical pesticides on fruit and vegetables has serious longterm effects on human health and environment and can result in resistant pathogen strains. The search for biopesticides using microbial antagonists and natural plant products has subsequently become more important as viable alternatives to control postharvest diseases. In this study, besides documenting the preharvest citrus cultivation practices, pests and postharvest disease incidences in Ethiopia, extracts from two plant species and three microbial antagonists have been documented as a breakthrough postharvest biocontrol agents. Besides controlling citrus infection, the semi‐commercial application of antagonists and plant extracts has also improved fruit quality and may provide a commercial solution for citrus industry world wide. This book will provide substantial information to Citrus Producing Companies, Agricultural Field Experts, Plant Pathologists, Biocontrol Product Processing Experts and Scientists interested in the field.
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    Control of Penicillium digitatum on Citrus Fruit Using Two Plant Extracts and Study of Their Mode of Action
    (Springer, 2007-05-07) Mekbib, Sissay Bekele; Regnier, Thierry J. C.; Korsten, Lise
    Extracts from two plants from Ethiopia, Withania somnifera and Acacia seyal, were evaluated for their potential as natural biopesticides and to study their mode of action. Methanolic extracts of these plants were tested in vivo on citrus fruit for their efficacy to control Penicillium digitatum when applied on wounded or unwounded fruit surfaces. Relative to the control, 70% and 75% of wound – inoculated fruit did not develop decay symptoms for up to 21 days of storage at 25◦C and >85% r.h. An increase in cell wall-bound phenolics was evident in wounded fruit treated with plant extracts and inoculated with a spore suspension of P. digitatum. Scanning electron microscopy revealed deposition of crystalline plant material sticking to the pathogen and around the wound site. The application of the plant extracts increased the epiphytic background total microbial population but decreased diversity. KEY WORDS: Citrus fruit; postharvest diseases; natural compounds; plant phenolics; host resistance.
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    Efficacy and mode of action of yeast antagonists for control of Penicillium digitatum in oranges
    (Brazilian Phytopathological Society, 2011-08) Mekbib, Sissay Bekele; Thierry, J. C.; Regnier; Korsten, Lise
    Three yeast antagonists (two strains of Cryptococcus laurentii and one of Candida sake) from orange trees reduced incidence of green mold by 80 to 95% when tested in wounded orange fruits inoculated with Penicillium digitatum and incubated at 7ºC for 30 days. The yeasts inhibited conidial germination of the pathogen, but did not kill the spores. Effectiveness of the three yeasts as antagonists was associated in part with their ability to rapidly colonize wound sites, despite low nutrient availability. Observations suggested that production of extracellular matrix by the yeasts may have facilitated rapid wound colonization. Germination of P. digitatum conidia was significantly inhibited when the pathogen and antagonists were in direct physical contact in a
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    Efficacy of Cellulose Degrading Microbial Strains on the Decomposition of Sewage Water Microalgae for the Production of Biogas
    (International Journal of Sciences: Basic and Applied Research (IJSBAR), 2014-12) Mekbib, Sissay Bekele; Ayele, Adebe Seyoum; Mosotho, George J.; Tebello, Samosamo
    Sewage water microalgae are potential sources of feed stock for the production of biofuel. In this study, six treatment combinations of microbial strains (C, N1 and N2) in single and combined treatments were used in a 5L plastic container as anaerobic digester. The use of sewage water microalgae alone was used as a negative control; and a separate application of effective microorganisms (EM) were used for comparison. A volume of 3L sewage water suspension containing 300g of microalgae biomass were used in all plastic containers as a feedstock. All treatment applications including the control showed some activity of pressure development in each bag per treatment per cycle except the combined treatment of strain (C, N1, N2). Significant volume of biogas production (4-5L/300g)) and pressure development (517.80 and 544.35 Nm-2 was observed in the first cycle when using cellulose degrading microorganism (C) alone and the combined treatment with nitrogen fixing strain (N1), respectively. High efficacy of shortening the retention time was observed while using strain C alone and combined treatment of C+N1 compared to other treatments including the control. Overall, strain C exhibited an increase of the final gas volume by 148.6% utilizing 60% of the microalgae biomass compared to the control. These results highlight the importance of the tested strains on efficiency of converting these algae to biofuel. However, further investigation of strain efficiency in a pilot scale application, outside the laboratory is recommended.
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    Evaluation of Ethiopian plant extracts, Acacia seyal and Withania somnifera, to control green mould and ensure quality maintenance of citrus (Citrus sinensis L.)
    (EDP Sciences, 2009) Mekbib, Sissay Bekele; Regnier; Thierry, J. C.; Korsten, Lise; Sivakumar, Dharini
    Green mould, Penicillium digitatum (Pers.: Fr.) Sacc., causes economically important postharvest disease in citrus. Materials and methods. Ethiopian plant extracts of Acacia seyal (Del. Var. Seyal) and Withania somnifera (L.) Dual were used to test the control of green mould in wound-inoculated fruit, stored for 21 d at 7 °C and at > 85% RH. The chemical compositions of the two extracts were determined using high-performance chromatography. Thereafter, freshly harvested (naturally infected) fruit were subjected to different postharvest treatments and stored for 50 d to investigate the effects of the two plant extracts on fruit quality parameters. Treatments included (pre-wax + leaf extracts), (wax + leaf extracts incorporated into wax, Citrosol A®), (leaf extract alone), (fruit washed in chlorinated water at 5.25%), (untreated fruit) and (commercially treated fruit). Results. Extracts of A. seyal and W. somnifera reduced the incidence of green mould by 56.1% and 50%, respectively, in wound-inoculated fruit. A. seyal extract contained a high concentration of gallic acid (60.3 mg·mL–1) whilst W. somnifera contained low concentrations of caffeic acid (8.7 mg·mL–1), salicylic acid (6.3 mg·mL–1) and 3,4 dihydroxy benzoic acid (3.8 mg·mL–1). Green mould was absent in naturally infected fruit subjected to (pre-wax + leaf extracts), (wax mixed with leaf extracts) and (leaf extracts) treatments. (Pre-wax + leaf extracts) and (wax mixed with leaf extract) treatments significantly reduced weight loss; retained firmness and colour; and they maintained eating qualities and a maturity index (SSC/TA) similar to commercial treatment. Conclusion. Both extracts of A. seyal and W. somnifera showed potential to be used as an alternative in combined applications with wax application under low temperature storage to replace synthetic fungicides, to ultimately control green mould and retain overall fruit quality.
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    In vitro antimicrobial assay of selected medicinal plants against medically important plant and food-borne pathogens
    (Journal of Medicinal Plants Studies, 2016) Mekbib, Sissay Bekele
    The traditional use of plant materials for treatment of human ailments dates back to prehistoric times. In this study, the antipathogenic activity of 37 extracts of 23 plant species, which originally were used to control citrus pre-harvest diseases and human aliments are reported. An in vitro screening for antimicrobial activity was conducted against seven plant pathogens and five food-borne pathogens. In total, 21 extracts from 13 plant species exhibited some degree of antimicrobial activity to at least one pathogen. Of these, six species, i.e. Achyranthes aspera, Tribulus terrestris, Acacia seyal, Dolichos oliveri, Cissus quadrangularis and Mirabilis jalapa are species with no known previous reports of antimicrobial activity against the tested pathogens. The minimum inhibitory concentration (MIC) of eight selected plant extracts were found to be between 1:2 and 1:5 (v: v). none of the extracts inhibited Escherichia coli or Erwinia carotovora. On the other hand, three plant extracts inhibited a bacterial strain with complete resistance to all antibiotics tested. Further elucidation of the active ingredients of these plant extracts is commendable for practical utility and control of resistance development.
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    Isolation, Molecular Characterization and Growth Promoting Activity of Free Living Diazotrophs Screened from Soils of Lesotho
    (Academia Publishing, 2016-02) Monokoane, P. C.; Mekbib, Sissay Bekele; Haiying, Li
    Thirty six free living diazotrophic isolates represented from different soil pH (5 to 7.22) of Lesotho were characterized. A nitrogen free medium was used to screen nitrogen fixing diazotrophs. Strains were classified into three groups as Azospirillum, Azotobacter and Bacillus spp based on their biochemical and molecular characteristics. All the diazotrophic groups showed some degree of nitrogenase activity when assayed using acetylene (C2H2) reduction assay and production of Indole Acetic Acid (IAA) when screened for PGPR traits. Despite the strain variability, significantly higher nitrogenase activity (190.20 nmol/mL-1h-1) was exhibited by strain NUL3-2 (Azospirillum spp), which in contrary exhibited lower amount of IAA production (0.032 mg ml-1) compared to strain MAF7-1 (0.448 mg ml-1) from the group of Azotobacter spp. Further evaluation of strains efficacy for plant growth promotion activity is commendable under greenhouse experimentation for potential use of these strains as biofertilizer.
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    Laboratory assessment of insecticidal properties of Tagetes minuta crude extracts against Brevicoryne brassicae on cabbage
    (Journal of Entomology and Nematology, 2013) Phoofolo, M. W.; Mabaleha, S.; Mekbib, Sissay Bekele
    The cabbage aphid, Brevicoryne brassicae is one of the most serious insect pests of cabbage in Lesotho. Chemical insecticides for efficient control of this pest are often unaffordable for resource-poor farmers. As a first step in a search for effective pest management techniques that can be affordable and easily available to these farmers, the aphicidal activities of Tagetes minuta crude extracts were evaluated against the cabbage aphid. A comparison was made on lethal and sub-lethal effects of T. minuta crude extracts from acetone, methanol, water and a mixture of acetone/methanol/water (7:7:1, v:v). The solvent system that produced the most toxic extract was the mixture, followed by methanol and water, whereas acetone produced the least toxic extract. The sub-lethal effect on cabbage aphid fecundity was well described by linear regression equations that showed significant reduction in fecundity as the concentration of crude extracts increased. The extract from the mixture solvent system had the strongest effect on fecundity.
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    Laboratory assessment of insecticidal properties of Tagetes minuta crude extracts against Brevicoryne brassicae on cabbage
    (Academic Journals, 2013-10) Mekbib, Sissay Bekele; Phoofolo, M. W.; Mabaleha, S.
    The cabbage aphid, Brevicoryne brassicae is one of the most serious insect pests of cabbage in Lesotho. Chemical insecticides for efficient control of this pest are often unaffordable for resource-poor farmers. As a first step in a search for effective pest management techniques that can be affordable and easily available to these farmers, the aphicidal activities of Tagetes minuta crude extracts were evaluated against the cabbage aphid. A comparison was made on lethal and sub-lethal effects of T. minuta crude extracts from acetone, methanol, water and a mixture of acetone/methanol/water (7:7:1, v:v). The solvent system that produced the most toxic extract was the mixture, followed by methanol and water, whereas acetone produced the least toxic extract. The sub-lethal effect on cabbage aphid fecundity was well described by linear regression equations that showed significant reduction in fecundity as the concentration of crude extracts increased. The extract from the mixture solvent system had the strongest effect on fecundity.
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    Machobane Farming System and its Relevance to Climate Change Policy in Lesotho
    (African Technology Policy Studies Network, 2012) Mekbib, Sissay Bekele; Alaleye, Adesola O.; Mokhothu, Motlatsi N.; Johane, Masia; Tilai, Spirit B.; Wondimu, Taddese
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    Microbial and physico-chemical evaluation of soils from different farming systems practicing fields in Lesotho and the adaptive capacity of Machobane Farming System to climate change
    (Academic Journals, 2015) Mekbib, Sissay Bekele; Olaleye, Adesola O.; Johane, Masia; Wondimu, Taddese
    In Lesotho, agriculture remains a major source of income for more than 80% of rural population. The arable land accounts for about 9% of the total land area and the current crop yields are half the level achieved in the late 1970s. Despite its contribution to Lesotho’s development, the rural economy has been languishing due to poor land management and farming practices, declining soil fertility, poor weather conditions and poor management of water resources. Communities living in marginal lands and whose livelihoods are highly dependent on natural resources are among the most vulnerable to climate change. In Lesotho, about six farming technologies, namely, block farming, mono-cropping, conservation farming, keyhole garden, double digging and the Machobane Farming systems are practiced. We assessed the distribution and diversity of Bacillus spp., the non-symbiotic Nitrogen Fixing Bacteria (NFB) and physico-chemical variables including soil texture, pH, organic carbon, and available phosphorus as quality indicators of soils from various farming systems in Lesotho in an attempt to elucidate the adaptive capacity of various farming systems to climate change. Amongst the six farming systems assessed, the Machobane Farming System (MFS) practicing fields exhibited significant level of soil quality improvement in microbial composition and physico-chemical property compared to other farming systems. These findings provide, for the first time, scientific evidence that the MFS, which combines indigenous knowledge and technology, may show better resilience to climate change for high and sustainable production of variety of crops throughout the year.
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    Microbial and Physicochemical Characterization of Maize and Wheat Flour from a Milling Company, Lesotho
    (FoodHACCP.com Publishing, 2013) Ntuli, V.; Mekbib, Sissay Bekele; Asita, A. O.; Molebatsi, Ntseliseng; Makotoko, Makotoko; Chatanga, Peter
    Maize meal flour and wheat flour are the most widely consumed cereals in Lesotho. The present study was undertaken to investigate the physicochemical and microbiological quality of special, super and extra super brands of maize meal flour; cake, white wheat and whole brown wheat brands of wheat flour produced by a mill company in Maseru, Lesotho. Three samples of each flour were collected on each of five sampling trips during January to May 2012, making a total of 90 samples, and were analysed physico-chemically for ash, fat, protein, moisture content and pH. Microbiologically, total plate count, total coliforms, Bacillus cereus, Salmonella spp, E. coli, yeasts and moulds were also determined. A series of biochemical tests were done to characterize the isolated micro-flora. Moisture content (9.89±0.76% to 13.31±0.64%) and pH (5.83±0.06 to 6.40±0.12) of the flours were within recommended legal limits. However, fat content (33% (n=90)) in maize samples exceeded the maximum recommended limit. The fat content (2.00±0.08% to 5.29±0.10%) of all maize meal brands was significantly higher (P<0.05) than that of wheat flour (0.90±0.03% to 1.87±0.02%). Protein content in maize meal was significantly lower than that of wheat flour, ranging from 7.01±0.91% to 9.64±0.09%. Ash content for the samples ranged from 0.29-1.21%. Statistically, bacterial counts in the different brands of flours showed significant differences (p < 0.05). In a more qualitative assessment, microbes of the genera Escherichia, Klebsiella, Aerobacter, Enterobacter, Salmonella, Bacillus, Aspergillus, Penicillium, Fusarium, Candida, Saccharomyces and Rhodotorula were identified in the flours. Pathogens (Bacillus cereus and Salmonella spp) and indicator organisms (coliforms and E. coli) were above World Food Programm (WFP) recommended limits. This study highlighted the need for stringent cleaning and sanitation regimes to be fully implemented in such companies for consumer safety and public health protection.
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    Qualitative Assessment of Livestock Faeces and Sewage for Antibiotic Resistant Strains of E. coli in Roma, Lesotho
    (Greener Journals, 2013) Mekbib, Sissay Bekele; Marole, T. A.; Asita, A. O.
    Sewage water (SW) and fresh livestock faeces: Chicken (ChNF), Sheep (SF), and Cattle (CF) were taken randomly from the farm of the National University of Lesotho aseptically during the 2012 academic year. Twenty ml of sewage water or 20 grams of fresh animal faeces was dissolved in 80 ml of sterilized Ringer�s solution and serially diluted. A 0.1 ml of sample suspension at 10-4 dilution was spread plated on Nutrient Agar (NA) and Eosine Methyl Blue (EMB) and plates were incubated for 24-48h at 24 and 37�C, respectively. A disc diffusion method was used to test the reaction of selected strains of Enterobacteriaceae to nine antibiotics. In total, 24 strains under Enterobacteriaceae were isolated from the respective sources and the number of each that were Escherichia coli, as confirmed by the biochemical tests were: SW (7 and 3); ChNF (5 and 3); SF (8 and 6) and CF (4 and 2). Thirteen E. coli strains fermented lactose and were Catalase positive, while only one E. coli strain from SW was non-lactose fermenter and Catalase negative. The lethal potencies, as number of isolates sensitive to the 9 antibiotics, ranked as: Colistin = Amikacin (24/24) > Kanamycin (23/24) > Chloramphenicol (22/24) > Cefotaxime (21/24) > Sulphafurazole (7/24) > Methicillin (1/24) > Penicillin G = Rifampicin (0/24). Sensitivity of the E. coli strains ranked as follows, Colistin = Amikacin = Kanamycin (14/14) > Chloramphenicol (13/14) > Cefotaxime (12/14) > Sulphafurazole (6/14) > Methicillin (1/14) > Penicillin G = Rifampicin (0/14). This result showed that the development of antibiotic resistant E. coli strains, which can pass through food chain to humans and other organisms if stringent control measures are not taken. Strict quarantine procedures have to be applied to control such potential health risks.
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    Qualitative Assessment of Livestock Faeces and Sewage for Antibiotic Resistant Strains of E. coli in Roma, Lesotho
    (Greener Journals, 2013) Mekbib, Sissay Bekele; Marole, T. A.; Asita, A. O.
    Sewage water (SW) and fresh livestock faeces: Chicken (ChNF), Sheep (SF), and Cattle (CF) were taken randomly from the farm of the National University of Lesotho aseptically during the 2012 academic year. Twenty ml of sewage water or 20 grams of fresh animal faeces was dissolved in 80 ml of sterilized Ringer’s solution and serially diluted. A 0.1 ml of sample suspension at 10-4 dilution was spread plated on Nutrient Agar (NA) and Eosine Methyl Blue (EMB) and plates were incubated for 24-48h at 24 and 37°C, respectively. A disc diffusion method was used to test the reaction of selected strains of Enterobacteriaceae to nine antibiotics. In total, 24 strains under Enterobacteriaceae were isolated from the respective sources and the number of each that were Escherichia coli, as confirmed by the biochemical tests were: SW (7 and 3); ChNF (5 and 3); SF (8 and 6) and CF (4 and 2). Thirteen E. coli strains fermented lactose and were Catalase positive, while only one E. coli strain from SW was non-lactose fermenter and Catalase negative. The lethal potencies, as number of isolates sensitive to the 9 antibiotics, ranked as: Colistin = Amikacin (24/24) > Kanamycin (23/24) > Chloramphenicol (22/24) > Cefotaxime (21/24) > Sulphafurazole (7/24) > Methicillin (1/24) > Penicillin G = Rifampicin (0/24). Sensitivity of the E. coli strains ranked as follows, Colistin = Amikacin = Kanamycin (14/14) > Chloramphenicol (13/14) > Cefotaxime (12/14) > Sulphafurazole (6/14) > Methicillin (1/14) > Penicillin G = Rifampicin (0/14). This result showed that the development of antibiotic resistant E. coli strains, which can pass through food chain to humans and other organisms if stringent control measures are not taken. Strict quarantine procedures have to be applied to control such potential health risks.
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    Screening of Diazotrophs as Plant Growth Promoters and Their Effect in the Development of Maize Seed
    (Canadian Center of Science and Education, 2016) Monokoane, P. C.; Mekbib, Sissay Bekele; Haiying, Li
    Free-living diazotrophs play an important role as plant growth promoters by supplementing nitrogen to deficient soils. In this study, six diazotrophic isolates were selected from 36 previously screened diazotrophic isolates for their mode of action to promote plant growth. A nitrogen free medium was used to screen nitrogen fixing diazotrophs. All strains have exhibited some activity of indole-3-acetic acid production. Strain MAF7-1 shown the highest (0.448 mg ml-1), while strain NUL3-2 exhibited the least (0.032 mg ml-1) production of IAA. Though all isolates were unable to solubilize inorganic phosphate, were able to inhibit the growth of Fusarium oxysporum that causes wilting to plants. There was no significant difference in maize seed germination vigour and rate. However, MAF7-1 had better germination rate and seed vigour (27.5%) when compared to the control (16%). Except strain NUL3-2, all showed significant increase of root length and dry weight of maize seedlings. Therefore, the choice of strain to be used for production of biofertilizer should not only be based on the nitrogenase activity, but also on ability to produce phytohormones. Strain NUL3-2, MAF7-1 and MAF7-3 are potential strains that can be used in the production of biofertilizer. Further study of these strains in depth as plant growth agents and biofertilizer is commendable for future application.