The whitefly Bemisia tabaci species complex has been well documented as one of the
most economically important emergent plant virus vectors, through serious feeding
damage to its broad range of plant hosts and transmission of plant viruses to important
agricultural crops. It has been shown to have associations with endosymbionts which
have significant effects on the insect fitness. The purpose of this study was to provide
information for the biotype and secondary endosymbiont distribution for B. tabaci
populations in the relatively unstudied Arabian peninsula. The geographical localization
and variation in endosymbiont populations across the region were identified using a
sequence-driven analysis of the population genetics of the secondary endosymbiont. Live
field specimens were collected from 22 different locations in the region and preserved in
70% ethanol for genetic studies. Previously established procedures were used to extract
and purify total insect DNA from 24-30 individual whiteflies for each location (Frohlich
et al., 1999; Chiel et al., 2007). Specimens were subjected to PCR amplification using the
respective 16S rDNAprimers for the Rickettsia, Hamiltonella, and Wolbachia to amplify
endosymbiont DNA. PCR was run with primers for the highly conserved whitefly
mitochondrial cytochrome oxidase subunit I (COI) gene for biotyping. Samples were
sequenced using the Sanger method and the data analyzed to correlate the presence,
prevalence and geographical distribution of endosymbionts in B. tabaci. Phylogenies
5
were constructed to track evolutionary differences amongst the endosymbionts and
insects and how they have influenced the evolution of the regional populations. Samples
were characterized by differences in the genomes and endosymbionts of common
whitefly ‘biotypes’ that have different host plant preferences, vector capacities and
insecticide resistance characteristics. It was found that the B biotype is the predominant
haplotype, with no evidence of the Q biotype. All endosymbionts were detected, with
Hamiltonella as the most predominant. Several instances of co-infection by two or more
endosymbionts were observed. Samples from the geographically isolated and
mountainous region of Fayfa demonstrated higher genetic variability compared to the
other locations, leading to the possible identification of a new haplotype, as well as the
first time identification of the A biotype in the region.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/293011 |
| Date | 05 1900 |
| Creators | Ragab, Alaa I. |
| Contributors | Fedoroff, Nina V., Biological and Environmental Sciences and Engineering (BESE) Division, Idris, Ali, Pain, Arnab |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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