Over centuries, crop domestication and improvement has led to modern
commercial agriculture. Agricultural biotechnology is considered by many a natural
step in the course of crop improvement by utilizing genetic engineering. Currently,
the global production of biotech crops is approximately 34% of global agriculture.
The major biotech crops in terms of production volumes are canola, cotton, maize
and soybean.
In Africa, South Africa is the only country to accept and commercially produce
genetically modified (GM) crop. The 2007, GM traits per crop with environmental
release status in South Africa included insect resistant (IR) and herbicide tolerant
(HT) cotton (including the stack for both traits) (90% of total cotton production), IR
and HT maize (including the stack for both traits) (57% of total production) and HT
soybean (80% of total production).
There are several factors that impact on the application of this technology in terms
of commercial as well as small scale farming. These include: intellectual property
rights, socio-economics, regulatory frameworks, agriculture, environment, niche
markets and cost benefit. Of all of these aspects, gene flow from GM to non-GM or
organic products, land races and wild relatives is a critical consideration. In this
study, the impact of potential pollen mediated gene flow (PPMGF) and pollen mediated gene flow (PMGF) was studied in GM soybean and maize, two of the
most important GM food crops in terms of production volumes.
In this study, GM gene flow was found to have occurred up to 0.9 m from a GM
source at two locations over two seasons, despite being considered a selfpollinating
crop (Greytown 2005/2006 and Delmas 2006/2007, respectively).
However, it was also found that GM soybean pollen was not wind borne and we
suggest that the gene flow observed was due to insect-mediation. Future studies
of PPMGF in South Africa should include a survey of insects present with the
potential to act as a pollen vector in soybean.
In the maize component of this study, molecular technology was used to detect GM
maize pollen up to 400 m from a GM pollen source. Furthermore, it was found that
out-crossing of GM to non-GM maize was possible at a distance of 300 m from the
GM field. Based on the statistical analysis of out-crossing data, I have determined
that the average theoretical zero (0.0001%) level of out-crossing was between 1.3
km and 2.0 km over different geographic locations. However, what was
unexpected is the difference in out-crossing per location for a specific direction.
For example, in Bainsvlei (2005/2007) for the ENE direction, the calculated
distance to achieve 0.01% out-crossing is 79 km, yet the average is 113 m.
Similarly in the second season for the same direction, the calculated distance is
956 m and the average is 135 m. The implication of these data is that it is not possible to establish a one size fits all
isolation distance to minimize or prevent gene flow. Different threshold levels of
commingling require different isolations distances and should be determined by the
acceptable level of tolerance for commingling. For non-GM production in South
Africa, based on the 1.0% threshold applied by the Department of Agriculture, I
suggest a minimum isolation distance of between 120 m up to 200 m, assuming
that the weather patterns are comparable to those of the current study as well as
that the non-GM seed being planted contains 0% GM. However, for more stringent
thresholds, the isolation distance would need to be extended.
For organic crop production, at 0% adventitious GM, as well as field trials of
second and third generation GMOs, it is suggested that the isolation distance be
set at a minimum of 1.5 km and 2.0 km, respectively. In addition, for non-GM seed
production (with a mandatory 0% tolerance so as not to contravene patents) I
recommend a 1.5 km isolation distance. These suggested isolation distances are
based on the absence of time isolation. It is hoped that this study will help to
inform regulatory as well as on farm decision making and that it could be used as a
blueprint for other GM crops, especially indigenous African crops such as sorghum
and cassava.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-09182009-144447 |
| Date | 18 September 2009 |
| Creators | Chetty, Lukeshni |
| Contributors | Prof CD Viljoen |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-09182009-144447/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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