Browsing by Author "Ekesi, S."

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    Genetic diversity of aphid (Hemiptera: Aphididae) species attacking amaranth and nightshades in different agro-ecological zones of Kenya and Tanzania
    (Entomological Society of Southern Africa, 2018-12) Kipnyargis, Alex C.; Kenya, Eucharia U.; Khamis, F. M.; Ekesi, S.; Fiaboe, K.K.M.
    Aphids are major pests of African indigenous vegetables. Information on the genetic diversity and the role of host crop and environmental differentiation in their diversity in East Africa is scanty. The knowledge on genetic diversity is a critical component in the development of sound and sustainable integrated pest management strategy, from detection to control. A portion of the mitochondrial cytochrome c oxidase subunit I (COI) gene was used to characterise the species of aphids on amaranth and nightshades at different agro-ecological zones of Kenya and Tanzania. Aphid samples were collected in localities growing the vegetables in low, mid and high altitude agro-ecological zones. Total DNA was isolated and amplified using universal barcoding primers targeting the 5’ end of the COI barcode region. Nucleotide sequences of the COI barcode, using the Basic Local Alignment Search Tool model, found high homology to four species of aphids: Myzus persicae, Aphis fabae, Aphis craccivora and Macrosiphum euphorbiae. Three subspecies of the A. fabae were also detected. Intraspecific diversity depicted M. euphorbiae having the lowest value, while A. fabae showed the highest diversity. Interspecific diversity between A. fabae and A. craccivora was the lowest while between A. craccivora and M. persicae it was the highest. The phylogenetic tree showed each species clustering together irrespective of the host crop or site where collected. Principal component analysis and haplotype network analyses confirmed these results. Low genetic diversity revealed by COI suggests that the environment or host crop contribute less to the genetic diversity of aphids in both countries
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    Infestation Levels and Molecular Identifcation Based on Mitochondrial COI Barcode Region of Five Invasive Gelechiidae Pest Species in Kenya
    (Oxford University Press, 2018-06) Kinyanjui, G; Khamis, F. M.; Ombura, F. L. O.; Kenya, Eucharia, U.; Ekesi, S.; Mohamed, S. A.
    Invasive Gelechiidae pest species, namely Tuta absoluta, Phthorimaea operculella, Aproaerema simplixella, Sitotroga cerealella, and Pectinophora gossypiella are among the major constraints hampering agricultural economy in Kenya. Infestation levels were determined on respective host crops sampled from different localities and P. operculella recorded the highest infestation of 68.00 ± 4.92% on stored potato. Aproaerema simplixella and T. absoluta accounted for 61.33 ± 5.35% and 51.56 ± 5.22% maximal infestation on groundnuts and tomato leaves, respectively. Stored maize was signifcantly infested by S. cerealella (54.33 ± 5.31%) while no infestation was observed on the freshly harvested grains. Infestation on open bolls by P. gossypiella was relatively low (6.11 ± 3.46%) compared to Anatrachyntis simplex (45.67 ± 7.84%) that emerged as the key pest of cotton. The species were discriminated based on sequence similarities, evolutionary divergences, and phylogenetic analyses. A 658-bp fragment of mitochondrial cytochrome c oxidase subunit I (COI) gene was obtained from 302 specimens. Generally, genetic variations were low within and between Gelechiid populations, with an average of 0.02% and all intraspecifc divergences were less than 2% except for S. cerealella. The Gelechiids data set generated eight Barcode Index Numbers (BINs), fve of which were concordant and three belonging to S. cerealella were singleton. All species were separated into distinct clusters on a maximum likelihood tree. Data on infestation levels will be useful in defning the pest status of these Gelechiids in Kenya. DNA barcoding is also presented as a valuable tool to complement traditional taxonomy for rapid and accurate identifcation of these species of agronomic interest.