The re-evaluation of pollen mediated gene flow within small grain

[摘要] ENGLISH ABSTRACT: South Africa is one of the few countries within Africa that have introduced genetically modified (GM) crops, and have been growing first generation GM crops since 1997 (Gouse et al. 2005). Within South Africa no emphasis has yet been set on the co-existence to establish management practices for the effective isolation of GM- and non-GM crops (Viljoen & Chetty 2011). There are currently no GM wheat or triticale varieties available for commercial production, but there are transgenic wheat and triticale varieties that are being successfully developed and field tested (Doshi et al. 2007; Kavanagh et al. 2012; Loureiro et al. 2012; Wree & Sauer 2015). The aim of this study was to determine the crossability as well as the potential of pollen mediated gene flow between wheat and triticale under dry-land conditions within the Western Cape.A Nelder wheel field trial was conducted at Mariondahl experimental station, Stellenbosch, South Africa, that comprised of a central pollen donor block (CPDB), containing blue aleurone triticale and purple pericarp wheat, which was surrounded by eight pollen receptor arms all orientated in the cardinal and intercardinal wind directions. Each arm was 66.25 meters in length, making the total area covered by the field trial 13788.65m2. The F1 seed that was harvested from the Nelder wheel field trial was planted at Welgevallen experimental farm, Stellenbosch, South Africa, and screened for hybridization and outcrossing events. The F1 spring wheat progeny were screened as pooled samples using molecular marker, Cfe53. Individual F1 spring wheat samples were also screened using molecular marker (Cfe53) to confirm the pooled sample results, but technical difficulties were than encountered with the molecular marker. The molecular marker results were then confirmed through chromosome visualisations. The F1 spring triticale progeny was screened morphologically for outcrossing events by the expression of blue pigmentation within the seed.Within this study a high amount of outcrossing and hybridization that was observed within the F1 wheat progeny (30-100%). The F1 spring triticale, outcrossing percentages was observed that ranged between 0.58% and 8.32%, with an average of 2.38%. Significant differences were calculated between the different wind directions, as well as between the different distances from the CPDB for the spring triticale. A correlation was also observed between the prevailing wind direction and speed with the pollen mediated gene flow (PMGF). PMGF at 66.25m from the CPDB indicates that pollen would have remained viable and that gene flow would have occurred past this point had the study extended past this distance from the CPDB. The 5% GM labelling threshold that is stipulated in Regulation 293 (2011), under the South African Consumers Protections Acts of 2008 (Acts online 2013) will be maintained within 66.25m from the pollen source. As the highest outcrossing percentage (OC%) that was obtained at 66.25m form the pollen source was 3.8% in the South-West arm. Isolation distances of more than 66.25m could be further investigated to obtain OC% of less than 1% in order for conventional farmers planting next to GM crops to be able to label their crops as GM free. The effect of temporal isolation and the use of physical barriers (i.e. other crops or bare ground) could also be further investigated and optimised to reduce PMGF and maintain the current GM thresholds.

[发布机构] Stellenbosch University