Bt-maize is engineered to express insecticidal toxins derived from the bacterium Bacillus
thuringiensis and has been shown to be very effective against pests like Busseola fusca.
However, resistance of this pest against Bt-maize has developed and spread throughout
South Africa. This study was inspired by the lack of knowledge over the microorganisms
associated with the gut of these insects as they play a vital role in insect growth and
development. Microbial-derived enzymes may have a role during an insect‟s adaption in
different environmental conditions and to new diets. Previous studies suggest (1) that gut
bacteria are required for B. thuringiensis-induced mortality in most Lepidoptera species and
(2) that the toxicity of B. thuringiensis depends on microbial community interactions within the
gut. The aim of this study was to determine the microbial diversity present in the midgut of B.
fusca larvae occurring in maize. Busseola fusca larvae were collected from 30 sites
throughout South Africa and dissected to collect their midgut contents. Serial dilutions were
made of the contents and spread plated onto nutrient agar after which morphotypes were
identified. One-hundred and five morphotypes were identified; DNA were extracted from the
selected morphotypes and subjected to PCR analysis followed by secquencing. Sequencing
results revealed the dominance of Enterococcus spp., specifically Enterococcus casseliflavus
and Enterococcus gallinarum, Klebsiella spp., espesially Klebsiella pneumoniae and
Klebsiella oxytoca and Bacillus spp. such as .B. thuringiensis and B. subtilis. Other
organisms isolated, included Achromobacter spp., Brevudimonas spp., Caulobacter spp.,
Enterobacter spp., Halomonas spp., Ochrobactrum spp., Pantoea spp., Pseudomonas spp.,
Serratia spp., Stenotrophomonas spp., Arthrobacter spp., Brevibacterium spp., Leucobacter
spp., Microbacterium spp., Planomicrobium spp. and Staphylococcus spp. The microbial
diversity of larvae collected at the respective sampling sites were determined with the
Shannon diversity index. The data were compared to several factors regarding the sampling
sites. No significant differences were observed between the microbial diversities isolated at
the respective sites. This may imply that the microbial community within B. fusca larvae are
relative consistent throughout the maize production area. It is important to understand the
distribution and structure of gut microbial communities within insects and whether the gut
community is influenced by the geographical distribution of the insects. A better
understanding of the distribution of the insects and community structure of their gut
microbiota may aid in the development of better insect control strategies. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/15566 |
| Date | January 2015 |
| Creators | Snyman, Maxi |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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