RP-Department of Plant and Microbial Sciences
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Browsing RP-Department of Plant and Microbial Sciences by Subject "Aflatoxins"
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Item Antifungal Effects of Ocimum Kilimandscharicum Oil on Aspergillus Flavus Infecting Maize after Harvest(Maximum Academic Press, 2023) Kaguchia, SM; Birgen, JK; Lang’at-Thoruwa, C; Akwa, TEMaize is consumed throughout the year in Kenya. Storage facilities of Maize vary with the economic status of the producers. Poor resource producers are likely to have unsuitable storage facilities whose conditions may predispose stored maize to post-harvest fungal infections. The most frequently encountered fungus in stored maize is Aspergillus flavus which produces aflatoxins that causes teratogenic, carcinogenic, mutagenic and hepatotoxic problems. Fungicides are used to control post-harvest fungi, but these have health implications. Hence an alternative safe method is the use of plant-based products which have anti-fungal compounds. This study was therefore designed to evaluate growth inhibitory effects of Ocimum kilimandscharicum oil on Aspergillus flavus. The leaves were collected from the plants growing naturally in Ruiru in Kiambu County, and the leaves were air dried in a shed, and oil was extracted through hydro-distillation. A total of 80 kg of threshed stored maize collected from randomly selected farms in Murang’a County were used to isolate Aspergillus flavus. Fungal growth experiments were done on PDA amended with different concentrations of the oil. Significant (p ˂ 0.001) inhibition of fungal radial growth occurred at oil concentration of 3.33 ul/ml. However, concentrations above 6.67ul/ml totally inhibited the growth of the fungus. Similarly, significantly (p ˂ 0.001) large zones of inhibition were observed in the highest concentration of 400 ul/ml. From the results, it can be concluded that O. kilimandscharicum oil acts against Aspergillus flavus and is a potential source for developing an antifungal agent. It is recommended that the efficacy of this oil needs to be tested on other post-harvest fungiItem 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 Efficacy of selected medicinal plants from Eastern Kenya against Aspergillus flavus(2014) Kiswii, M.T.; Monda, E. O.; Bii, Christine; Alakonya, Amos E.Aflatoxins are a major problem in Eastern Province of Kenya and Aspergillus flavus has been associated with frequent outbreaks of aflatoxicoses in this region. This study evaluated the efficacy of 15 selected medicinal plants from Eastern Kenya against A. flavus. Different concentrations of 1000mg/ml, 750mg/ml and 400mg/ml using Agar Well Diffusion Method were used. Plants found to have inhibition zones of more than 10mm at 400mg/ml had their bark further assayed for antifungal activity. Both the leaf and bark extracts that were found to be effective were assayed for minimum inhibition concentrations (MIC) and minimum fungicidal concentrations (MFC) using Sabouraund Dextrose broth (SDB) micro-dilution method. The methanolic leaf and bark extracts of the fifteen plants assayed displayed concentration depended antifungal activities that was comparable to that of the reference drug Miconazole at 10mg/ml. Leaf extracts showed better antifungal activity than the bark extracts. For instance, Boscia coriacea (mean 17.40mm) had the highest zone of inhibition followed by Zanthoxylem chalybeum (mean 17.20mm). For the bark extracts, Croton megalocarpus (mean 15.0mm) recorded significantly high antifungal activity while Tithonia diversfolia (mean 13.0mm) had the lowest at 400mg/ml. Senna siamea had the lowest MIC and MFC of 6.25mg/ml and 12.5mg/ml respectively. The preliminary phytochemical analysis of the 15 effective medicinal plants revealed the presence of bioactive compounds that included tannins, saponins, flavonoids, terpenoids, cardiac glycosides and alkaloids. The results obtained from the study could be used as a viable management strategy against A. flavus and aflatoxins in the region so as to ensure low mycotoxin exposure as well as low environmental pollutionItem A Review of Agricultural Aflatoxin Management Strategies and Emerging Innovations in Sub-Saharan Africa(Rural Outreach Program, 2016) Monda, E.O.; Alakonya, A.E.Aflatoxins are highly carcinogenic secondary metabolites produced by Aspergillus flavus, A. parasiticus and A. nomius. Aflatoxin contamination of food and animal feeds is, therefore, a major food security, food safety, trade, human and domestic animal health concern. Researchers worldwide have suggested various agriculture-based strategies to manage aflatoxigenic Aspergillus species and reduce contamination to safe levels. This paper reviews various agricultural strategies that could be employed to reduce contamination of aflatoxins in food crops and animal feeds, as well as the challenges faced by these reduction strategies. Among these strategies are innovations like AflasafeTM and solar grain driers. It is hoped that this critique will stimulate refinement of the existing aflatoxin control approaches and innovations to maximize their efficacy