Browsing by Author "Midega Charles Aura Odhiambo"

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    In Vitro Antifungal Activity of 'Desmodium Intortum' and 'D. Uncinatum' Root Extracts against Growth of Toxigenic 'Fusarium Verticillioides' and 'Aspergillus Flavus'
    (Southern Cross Publishers, 2020-12) Njeru Nancy Karimi; Midega Charles Aura Odhiambo; Muthomi James Wanjohi; Wagacha John Maina; Khan Zeyaur Rahman
    Maize grown under push-pull cropping system has been reported to contain lower concentrations of fumonisin and aflatoxin than maize monocrop. This study determined the inhibitory effect of desmodium root extracts on spore germination and radial growth of toxigenic 'Aspergillus flavus and Fusarium verticillioides'. 'Aspergillus flavus and F. verticillioides' were isolated from maize and soil and tested for ability to produce aflatoxin and fumonisin by inoculation on mycotoxin-free maize. Aflatoxin and fuminisin were detected and quantified by direct competitive ELISA. Desmodium roots were dried, ground to fine powder and extracted with methanol and dichloromethane and evaluated for anti-fungal activity by inhibition of spores of 'A. flavus and F. verticillioides' potato dextrose agar (PDA) medium. Isolates of F. verticillioides produced up to 599,741 mug/kg fumonisin while isolates of 'A. flavus' produced up to 199,184 mug/kg aflatoxin. Desmodium root extracts reduced germination of 'A. flavus spores and F. verticillioides' by 9.6% and 43.8%, respectively and reduced their respective colony radial growth by 15% and 57%. The results suggested that desmodium roots contain chemical compounds that inhibit growth of 'A. flavus and F. verticillioides'. This may explain the reduction in infection of maize with mycotoxin-producing fungi before harvest in push-pull cropping systems by reducing the pathogen inoculum in the soils. Determination of the active compounds in the root exudates is recommended.
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    Influence of Socio-Economic and Agronomic Factors on Aflatoxin and Fumonisin Contamination of Maize in Western Kenya
    (Willley Online Library, 2019-06-11) Njeru Nancy Karimi; Midega Charles Aura Odhiambo; Muthomi James Wanjohi; Wagacha John Maina; Khan Zeyaur Rahman
    Consumption of maize contaminated with mycotoxins has been associated with detrimental health effects. A farm survey covering 116 push-pull and 139 non-push-pull cropping systems was conducted to determine the socio-economic and agronomic factors that influence farmers’ knowledge on incidence and contamination of maize by ear rots and associated mycotoxins in western Kenya. All the respondents were smallholder farmers between the ages of 23 and 80 years, with 50% of them being female. Maize samples were collected from the standing crop in the field of each interviewed farmer and analyzed for aflatoxin and fumonisin. Only a small proportion of farmers had knowledge of aflatoxin and ear rots in maize. Overall, less than 20% of maize samples were contaminated with both aflatoxin and fumonisin, and more maize samples were contaminated with fumonisin as compared to aflatoxin. Proportions of maize samples containing higher than the acceptable Kenyan regulatory threshold (10 µg/kg) for aflatoxin and European Commission regulatory threshold (1,000) µg/kg for fumonisin were lower in maize samples from push-pull cropping system. Age of farmer and county of residence were significantly and positively associated with knowledge of aflatoxin, while cropping system, county of residence, and level of education were positively associated with knowledge of maize ear rots. There was strong correlation between knowledge of maize ear rots and knowledge of aflatoxin. Levels of both aflatoxin and fumonisin were significantly and positively associated with the use of diammonium phosphate (DAP) fertilizer at planting. Aflatoxin levels were also positively associated with stemborer damage. Agronomic practices were not significantly different between push-pull and non-push-pull farmers. However, use of DAP fertilizer was the most important agronomic factor since it was associated with both aflatoxin and fumonisin contamination of maize. These results imply that creating awareness is key to mitigation of ear rots and mycotoxin contamination of maize. The results also suggest that the levels of aflatoxin and fumonisin in maize in western Kenya were influenced both by pre-harvest agronomic practices and by the cropping system adopted, push-pull or not.