RP-Department of Plant and Microbial Sciences
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Browsing RP-Department of Plant and Microbial Sciences by Author "Alakonya, A. E."
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Item Downregulation of Transcription Factor Aflr in Aspergillus Flavus Confers Reduction to Aflatoxin Accumulation in Transgenic Maize With Alteration of Host Plant Architecture(Springer Berlin Heidelberg, 2015-04) Monda, E. O.; Masanga, J. O.; Matheka, J. M.; Omer, R. A.; Ommeh, S. C.; Alakonya, A. E.We report success of host-induced gene silencing in downregulation of aflatoxin biosynthesis in Aspergillus flavus infecting maize transformed with a hairpin construct targeting transcription factor aflR. Infestation of crops by aflatoxin-producing fungi results in economic losses as well as negative human and animal health effects. Currently, the control strategies against aflatoxin accumulation are not effective to the small holder farming systems in Africa and this has led to widespread aflatoxin exposure especially in rural populations of sub-Saharan Africa that rely on maize as a staple food crop. A recent strategy called host-induced gene silencing holds great potential for developing aflatoxin-resistant plant germplasm for the African context where farmers are unable to make further investments other than access to the germplasm. We transformed maize with a hairpin construct targeting the aflatoxin biosynthesis transcription factor aflR. The developed transgenic maize were challenged with an aflatoxigenic Aspergillus flavus strain from Eastern Kenya, a region endemic to aflatoxin outbreaks. Our results indicated that aflR was downregulated in A. flavus colonizing transgenic maize. Further, maize kernels from transgenic plants accumulated significantly lower levels of aflatoxins (14-fold) than those from wild type plants. Interestingly, we observed that our silencing cassette caused stunting and reduced kernel placement in the transgenic maize. This could have been due to “off-target” silencing of unintended genes in transformed plants by aflR siRNAs. Overall, this work indicates that host-induced gene silencing has potential in developing aflatoxin-resistant germplasm.Item 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 mycotoxinsItem 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.