Genetically modified (GM) maize was developed mainly to control lepidopteran pests
such as the maize stem borer (Busseola fusca) (Lepidoptera: Noctuidae). Since the
first commercialization of GM crops with insecticidal properties, possible non-target
effects such as the effect at the third trophic level on important predators for example
lacewing species (Chrysoperla spp.) have been of concern. Contradicting results
were reported in previous studies with regard to the effect of Cry 1Ab protein
produced by Bt maize on the performance of lacewings. Some studies found that Bt
proteins had no effect while others reported that C. carnea performed poorly if they
consumed prey that consumed Cry 1Ab protein. In South Africa one of the most
common chrysopid species in maize ecosystems is Chrysoperla pudica (Navás)
(Neuroptera: Chrysopidae). Evolution of Bt resistant pests, such as B. fusca in
South Africa facilitates a new pathway for exposure of predators to healthy prey that
consumes Cry 1Ab proteins. The aims of this study was to determine the effect of
the Cry 1Ab protein expressed in Bt maize on a non-target organism‟s (C. pudica)
biology via indirect exposure, and to determine the concentration of Cry 1Ab protein
in the plant, prey and predator. Chrysoperla pudica larvae were indirectly exposed
to the Bt-toxin through healthy Bt-maize feeding prey (B. fusca larvae) in two feeding
experiments and lacewing survival and life history parameters recorded. Bt had a
limited effect on some parameters that were evaluated. The larval and pupal periods
of C. pudica larvae that were exposed to the Bt-toxin had a significant difference
from that of the control treatment. The Bt-toxin had a significant effect on fecundity,
fertility and malformation after emergence of C. pudica adults of which larvae fed
only on Bt resistant B. fusca larvae, but not on the mortality rate. Cry 1Ab
concentration was the highest in the plant, followed by the prey and lacewing larvae.
This study showed that the Cry 1Ab protein had a slight adverse effect only on
certain life parameters of C. pudica, and that Cry 1Ab protein was hardly detectable
in C. pudica larvae. However, since this study represented a worst-case scenario
where diverse prey was not available, insignificant effects is expected under field
conditions where prey is diverse. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/10816 |
| Date | January 2014 |
| Creators | Warren, Jo-Ann Francis |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0025 seconds