Transgenic Sunflower - Genetics, Genomics and Breeding of Crop Plants - page 304

naturalized populations of H. petiolaris and H. annuus in central Argentina
(Poverene et al. 2002) giving evidence of crop-wild gene flow (Cantamutto et
al. 2003).
After the dissemination of these findings, the number of applications
for sunflower GM varieties release submitted to CONABIA drastically fell to
zero by 2005. Following the acknowledgement of existing naturalized wild
populations (Fonseca et al. 2004), the release of transgenic sunflower
varieties was presumed as improbable by the Argentine Sunflower
Association (ASAGIR) (Ingaramo 2006). A similar situation has taken place
since 2004 in the US, where the National Sunflower Association (NSA)
began to use the non-transgenic nature of sunflower crop to promote its
consumption. On the other hand, there is no clear position of the
International Sunflower Association on this subject ( www.isa.cetiom.fr ) .
9.6 Prospective View on Transgenic Sunflower Release
Most of the available transgenes and modulators that have been engineered
in plants could be expressed in sunflower. However, the traits that are being
studied in sunflower for environmental release are limited and mainly consist
of insect resistance, herbicide tolerance, and special compound synthesis.
Leaving aside product marketing considerations, sunflower crop
management would greatly benefit from the introduction of GM varieties
(Cantamutto and Poverene 2007).
Botanical files (Conner et al. 2003) would indicate a high ecological risk
for GM sunflower release because of the difficulty to keep transgenes
restricted within the crop. Being an outcrossing crop, complete isolation
demands distances of 5 Km (Anfinrud 1997) because pollen are carried by
insects. Likewise, its seeds disperse along wide distances by trucks and
machinery, forming ruderal populations also vulnerable to gene flow
(Reagon and Snow 2006; Ureta et al. 2008). As well as the drawback posed
by volunteer plants for following crops (Robinson 1978), sunflower can
develop ferality through sexually compatible crosses with five invading
relatives ( Table 9.5 ) , being perennial with tubers that can disperse to long
distances moving down along river banks (Bervillé et al. 2005).
Taking for granted food safety assessment by official regulatory systems
(Jaffe 2004) and the absence of unpredictable effects from transgene insertion
(Clark 2006), it is imperative to predict the environmental impact if
transgenes reach wild or feral relatives. Hybridization does not per se ensure
introgression; to introgress a transgene must have some ecological
implication, for example it may suppress a controlling element (Hails and
Morley 2005) or enhance fecundity in the receptive population (Lee and
Natesan 2006). However, introgression could result in neutral or null
depending on natural selection pressure (Chapman and Burke 2006).