Abstract:
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
