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

Van Zyl, Irma (2016-03)

Thesis (MSc)--Stellenbosch University, 2016.

Thesis

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.

AFRIKAANSE OPSOMMING: Suid Afrika is een van die min lande in Afrika wat van geneties gemodifiseerde (GM) gewasse gebruik maak, en verbou eerste generasie GM gewasse al sedert 1997 (Gouse et al. 2005). In Suid Afrika is daar tot hede nog geen klem geplaas op die mede bestaan en ontwikkeling van bestuur praktyke vir die effektiewe isolasie van GM en nie-GM gewasse nie (Viljoen & Chetty 2011). Daar is tans geen GM koring of korog variëteite beskikbaar vir kommersiële produksie nie, maar daar is transgeniese koring en korog variëteite wat suksesvol ontwikkel en in verskillende gebiede getoets word (Doshi et al. 2007; Kavanagh et al. 2012; Loureiro et al. 2012; Wree & Sauer 2015). Die doel van hierdie studie is om die uitkruisbaarheid sowel as die potensiaal van stuifmeel bemiddelde geen vloei tussen koring en korog onder droëland toestande in die Wes-Kaap te bepaal. ‘n Nelder wiel veld proef was uitgevoer by Mariondahl navorsing stasie, Stellenbosch, Suid Afrika, wat bestaan het uit 'n sentrale stuifmeel skenker blok (SSSB), wat blou aleurone korog en pers opperhuid koring bevat het, wat omring was deur agt stuifmeel ontvanger arms, wat almal georiënteerd was in die kardinale en inter-kardinale windrigtings. Elke arm was 66.25 meter lank, wat die totale gebied van die veld proef 13 788.65m2 maak. Die F1 nageslag wat vanaf die Nelder wiel veld proef geoes is, was oor geplant op Welgevallen proefplaas, Stellenbosch, Suid Afrika, waar verbastering en hibridisering gebeure geidentifiseer was. Uitkruising in die F1 koring nageslag was geidentifiseer deur saamgevoegde monsters te toets met met behulp van ‘n molekulêre merker, Cfe53. Individuele F1 koring monsters was ook getoets deur gebruik te maak van molekulêre merker (Cfe53) om die resultate van die saamgevoegde monsters te bevestig, maar die merker het begin probleme gee. Die resultate van die molekulêre merker was daarna bevestig deur chromosoom visualiserings. Hibridisering gebeure binne die F1 korog nageslag was morfologies geïdentifiseer deur die uitdrukking van blou pigmentasie binne die saad. Binne hierdie studie is 'n groot hoeveelheid hibridisering en verbastering waargeneem in die F1 koring nageslag (30-100%). By die F1 korog, was hibridisering persentasies waargeneem wat gewissel het tussen 0.58% en 8.32%. Beduidende verskille was bereken tussen die verskillende windrigtings, sowel as tussen die verskillende afstande vanaf die SSSB. 'n Korrelasie was ook waargeneem tussen die stuifmeel bemiddelde geen vloei (SBGV) en die heersende windrigting en spoed. Waargenome SBGV was 66.25m vanaf die SSSB en dui daarop dat die stuifmeel lewensvatbaar sou gebly het en dat SBGV sou kon plaasgevind het verby hierdie punt vanaf die SSSB, indien die afstand vanaf die SSSB verder verleng was. Die vasgestelde 5% drumpel vir die etikettering GM materiaal in nie-GM produkte, wat gestipuleer is in Regulasie 293 (2011), onder die Suid Afrikaanse Verbruikers Beskermings Wette van 2008 (Acts online 2013) sal binne 66.25m vanaf die stuifmeel bron gehandhaaf word. Aangesien die hoogste persentasie hibridisering (OC%) wat waargeneem was in hierdie studie by 65.25m vanaf die stuifmeel bron 3.8% was in die Suid-Wes arm. Isolasie afstande van meer as 66.25m kan ook verder ondersoek word om OC% van minder as 1% te behaal en so konvensionele boere in staat te stel om langs GM gewasse te plant en steeds hulle gewasse as GM vry te kan etiketteer. Die effek van tydelike isolasie sowel as die gebruik van fisiese skanse (bv. ander gewasse of oop grond) kan verder ondersoek en geoptimaliseer word om SBGV te verminder om huidige drumpel waardes te handhaaf.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98677
This item appears in the following collections: