Browsing by Author "Andika, Darius O."

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    Exploring the Changes of Resistant Genes Expression in Groundnuts (Arachis Hypogea) In Response to Aspergillus Flavus Exposure at Seedling Stage
    (2020-07) Okayo, Robert O.; Andika, Darius O.; Dida, Mathews M.; K’Otuto, George O.; Gichimu, Bernard M.
    Aspergillus flavus infect groundnut seeds and produce secondary metabolites, aflatoxins. The aflatoxins are associated with various diseases in domestic animals and humans globally. Mitigating the aflatoxin contamination in crops through the development of cultivars tolerant to fungus colonization and aflatoxin contamination has been considered the most costeffective measure. This research was conducted to ascertain that the resistance genes identified in the previous transcriptome analysis were involved in groundnut defense mechanisms to A. flavus infection. Eight genes were selected for additional scrutiny through the real time PCR on a groundnut seedling at an interval of 2 days within a 7-day period. The results indicate a network of gene expression patterns in a sequential order in both resistance and susceptible lines at a seedling stage. The peak expression level per gene indicates the time gene action was crucial. We conclude that these genes are involved in groundnut resistance to A. flavus infection and provide important targets for the molecular marker screening.
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    Isolation, characterization and identification of Diazinon degrading bacteria from the soil and gut of macrotermes
    (2013) Ogot, Hellen A.; Boga, Hamadi I.; Budambula, Nancy; Tsanuo, Muniru; Andika, Darius O.
    Diazinon degrading bacteria were isolated from the soil and gut of fungus cultivating termites Macrotermes michaelseni using MM7 media supplemented with pesticide as the sole source of carbon and energy. The isolates were gram negative rods the isolates from the soil were designated DS2, DS3 and DS5 while from termite gut was designated DT2. 16S rRNA gene sequence analysis showed that diazinon degrading isolate DS2 (from the soil) is closely related to Achromobacter xylosoxidan AF508101 (100%), isolate DT2 from termite gut is closely related to Klebsiella oxytoca AB004754 (99.7%). Whereas isolates DS3 and DS5 , both from the soil are closely related to p., AY082447 (99%). The ability of the isolates to degrade diazinon highlights their potential to be used in bioremediation.
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    Morphological and Molecular Characterization of Toxigenic Aspergillus flavus from Groundnut Kernels in Kenya
    (Hindawi, 2020-09) Okayo, Robert O.; Andika, Darius O.; Dida, Mathews M.; K’Otuto, George O.; Gichimu, Bernard M.
    Pathogenesis of Aspergillus flavus on important agricultural products is a key concern on human health due to the synthesis and secretion of the hazardous secondary metabolite, aflatoxin. &is study identified and further characterized aflatoxigenic A. flavus from groundnuts sampled from sundry shops in Kenya using integrated morphological and molecular approaches. &e groundnuts were plated on potato dextrose agar for isolation and morphological observation of A. flavus based on macroscopic and microscopic features. Molecular characterization was done through amplification and comparison of the partial sequence of the ITS1-5.8S-ITS2 region. &e expression analysis of aflR, aflS, aflD, aflP, and aflQ genes in the aflatoxin biosynthesis pathways was conducted to confirm the positive identification of A. flavus. &e gene expression also aided to delineate toxigenic isolates of A. flavus from atoxigenic ones. Morphologically, 18 isolates suspected to be A. flavus were identified. Out of these, 14 isolates successfully amplified the 500 bp ITS region of A. flavus or Aspergillus oryzae, while 4 isolates were not amplified. All the remaining 14 isolates expressed at least one of the aflatoxigenic genes but only 5 had all the genes expressed. Partial sequencing revealed that isolates 5, 11, 12, 13, and 15 had 99.2%, 97.6%, 98.4%, 97.5%, and 100% homology, respectively, to the A. flavus isolate LUOHE, ITS-5.8S-ITS2, obtained from the NCBI database. &e five isolates were accurate identification of atoxigenic A. flavus. Precise identification of toxigenic strains of A. flavus will be useful in establishing control strategies of the fungus in food products.