RP-Department of Plant and Microbial Sciences

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Browsing RP-Department of Plant and Microbial Sciences by Author "Ajanga, S."

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    Effect of Delayed Harvesting on Maize Ear Rot in Western Kenya
    (IDOSI Publications, 2008) Alakonya, A. E.; Monda, E. O.; Ajanga, S.
    Maize ear rot is an important disease in Kenya. Despite causing yield losses the ear rot fungi also contaminate infected grains with mycotoxins. In western Kenya, the leading maize producing region of the country, farmers habitually leave their maize in the field upon maturity so as it may dry, but the harvest season often coincides with the second rains and the result is often increased rotting. Using on farm experiments in farmers’ fields with 12 farmers at both Malava and Tongaren in Westen Kenya. Ten varieties were planted and harvested at 4, 8 and 12 week harvest time points after physiological maturity. Four farmers from every region were randomly selected at each harvest time point and their crop harvested. Relevant data that included percentage rotten grain, ear rot incidence, severity, borer incidence, lodging and drooping of ears was collected. The results showed that delayed harvesting increases ear rotting. Many ear rot resistance traits like closed ear tips, hard to lodge stems, drooping ears and resistance to insects were compromised when maize was left in the farm for longer periods of time. Farmers are therefore advised to harvest their maize at four weeks after physiological maturity to avoid further rotting and possible lethal contamination of grains by mycotoxins
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    Fumonisin b1 and aflatoxin b1 levels in kenyan maize
    (Journal of Plant Pathology, 2009) Alakonya, Amos E.; Monda, E. O.; Ajanga, S.
    Maize ear rot is an important disease of maize in Kenya. In this study fumonisin Bx (FBj) and aflatoxin Bx (AFBj) analysis were conducted on symptomless and rotten maize harvested at different harvest time points after physiological maturity (HTPAPM). Fusarium verti- cillioides dominated at all HTPAPM. Other fungi re- ported include Aspergillus flavus, Aspergillus parasiticus and Sternocarpella may dis. In 2001, FBX levels in symp- tomless maize ranged between 22 to 1348 pg/kg. Mean FBj levels at 4, 8, and 12 weeks HTPAPM for Malava were 56, 80 and 317 jig/kg respectively. In Tongaren during 2001 mean FBl levels of 41, 179 and 590 pg/kg were recorded at 4, 8, 12 week HTPAPM respectively. The FBj levels in rotten maize ranged from 39 to >5000 pg/kg and increased with HTPAPM. The highest AFB1 level was 17 pg/kg in rotten maize. The results suggest that delayed harvesting could increase FBX contamina- tion in maize. Maize ear rot, Fusarium verticillioides, As- pergillus flavus , mycotoxins, food safety.
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    Management of Fusarium verticillioides Root Infection Court in Maize Using Organic Soil Amendments
    (World Applied Sciences Journal, 2008) Alakonya, Amos E.; Monda, E. O.; Ajanga, S.
    Abstract: In this study the efficacy of various soil organic amendments were evaluated for their potential to manage Fusarium verticillioides root infections in maize. The soil organic amendments used were neem cake, sunflower cake, cotton cake, goat manure and farmyard manure. In a field experiment F. verticillioides was inoculated to seed holes with different soil organic amendments at planting. Soil and root samples were collected for mycological analysis at 10, 30 and 60 days after silking. Upon maturity maize was harvested at 4 and 8 weeks after physiological maturity where assorted data was collected. Rotten and symptomless maize samples were collected and subjected to mycological and mycotoxin analysis. Significantly high recovery rates of F. erticillioides from control soil and roots than in amended soil was evident. At 60 days after silking the percent recovery of F. verticillioides was reduced to even zero in some treatments indicating that organic soil amendments have a mechanism of suppressing the survival of F. verticilliodes in the soil and hence limit its root infection ability. Mycological analysis on symptomless kernels revealed high recovery of F. verticilliodes from in control plots than amended treatments indicating the ability of the amendment to manage root infections of F. verticilliodes. Mycotoxin analysis revealed widespread FB1 contamination across treatments and in both asymptomatic and rotten maize. Average FB1 in symptomless maize was 333.98 μg kg and 357.4 μg kg at 4th 1 1 and 8th weeks after physiological maturity respectively. All rotten maize samples had over 5000 μg kg 1 of FB .1Aflatoxins were only present in three samples at 4th week after physiological maturity. The results show that soil organic amendments could limit root infection by F. erticillioides however, it cannot if singly used as a management strategy against the pathogen guarantee 100% eradication of the pathogen and associated mycotoixins. This therefore calls for an integrated approach that could involve use of resistant hybrids, soil solarization, early land preparation, insect control, fungicide treated seed and good post harvest handling practices. Mycotoxin ignorant maize consumers in Africa especially need to be educated on the risks they face if they consume rotten maize given the very high levels of FB1 revealed in this study and elsewhere. Key words: Infection court Fumonisins Aflatoxins Organic soil amendments Ear rot fungi ELISA Zea mays Kenya
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    Use of organic soil amendments in management of fusarium moniliforme
    (African Crop Science Society, 2013) Alakonya, Amos E.; Monda, E. O.; Owino, P. O.; Ajanga, S.
    Efficacy of soil amendments in management of root infection by Fusarium moniliforme was evaluated in the greenhouse at Kenyatta University. The amendments used were neem cake, sunflower cake, cotton cake, goat manure, farmyard manure (Fym), and a combination of Fym with neem cake, sunflower cake, cotton cake, or goat manure. F. moniliforme used was isolated from kernels in western Kenya, a maize ear rot disease prevalent region. Seeds of a susceptible maize variety H622 seeds were used during the study. Non-amended soil acted as the control. Plants were harvested at 30,60 and 90 days after planting. At every interval, plant length, shoot dry weight, root dry weight were assessed. Pathogen recovery from the soil, roots, crown and node was also evaluated at the intervals. The results revealed that different soil organic amendments had significant effects on the pathogenecity of F. moniliforme and plant performance. Goat manure had significant suppressive effects on root infection when used singly, but the effects were less than those obtained from a mixture of goat/Farm yard manure. Efficacy of various amendments were rated as follows starting from the most to the least effective; goat, goat/Fym, neem/fym, cotton, Fym, cott/Fym, sun/fym, neem and sunflower respectively. In general organic amendments reduced the survival and infection of maize plants by F. moniliforme compared to controls. The population of F. moniliforme reduced gradually with time after planting. Results from this study suggest that the use of organic amendments might be a viable option in the management F. moniliforme in areas where the pathogen is prevalent. Key words: Fusarium moniliforme, ear rot, maize, soil organic amendments.
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    Variation in In vitro Fumonisin B1 Production by Different Fusarium verticillioides Isolates in Kenya
    (IDOSI Publications, 2008) Alakonya, A. E.; Monda, E. O.; Ajanga, S.
    Several Fusarium verticillioides isolates from different maize growing regions in Kenya were isolated and evaluated for their ability to produce fumonisin B1 (FB1 ) The toxin was quantified using a directly competitive ELISA method. There were differences in the ability of the various isolates to produce FB1 . Six isolates of F. verticillioides from every region produced varying amounts of FB in vitro.The overall mean FB1 level in positive isolates was 1513.3 μg kg-1 of all the isolates used in the study only 26% did not produce detectable levels of FB , whereas 74% produced varying amounts of FB1 between 69 to >5000 μg kg-1. Within every given region there was variation in the ability F. verticillioides isolates to produce FB1. Isolates from Malava, Tongaren and Kakamega showed great variation among themselves. All isolates from Kitale, Tongaren, Kakamega and Embu produced detectable levels of FB1 . This data puts to rest the speculation that F. verticilliodes isolates from Kenya may be low FB1 producers. Kenya and most countries that allow free movement of maize need to reconsider their free domestic movement policy in order to avoid introduction of prolific isolates in otherwise ‘pest free’ areas.