The biotechnology industry has recently developed Genetically Modified (GM) cultivars of squash Cucurbita that are resistant to several types of virus.  The USDA released and allowed the commercial use of virus resistant GM Cucurbita pepo cultivars.  There is evidence for gene flow between cultivated and wild species of Cucurbita.  The release of GM Cucurbita pepo by the USDA was based on the fact that the genes of resistance to the virus will not be able to escape and persist in natural populations.  However, no studies have evaluated the consequences that the release of genetically modified plants may have on natural populations of Cucurbita in a region of center of origin for this species.  Therefore, it is important to determine the ability of genes from GM plants to persist in natural populations and its consequences on the fitness of the progeny produced via hybridization.  The persistance of GM Cucurbita hybrids can become invasive and have the potential to become a pest in agricultural fields.  This study was conducted in Mexico which is the most important reservoir of genetic diversity of Cucurbita spp. in the world and is the center of origin of squash, Cucurbita pepo.  This study was design to evaluate the level of hybridization between Cucurbita pepo GM plants (Independence II) and C. argyrosperma sororia, by conducting a series of pollen competition experiments.  Cucurbita argyrosperma sororia is an endemic species of western Mexico.  Crosses involved mixtures of pollen from transgenic and wild pollen donors.  Seeds obtained from these crosses were planted in the greenhouse and paternity was determine using phenotypic and molecular markers.  We also measured the vigor of the progeny produced.

Results/Conclusions Our results indicate that Cucurbita pepo GM hybridize with the wild species of Cucurbita argyrosperma sororia.  Transgenic genes resistant to virus are transmitted to F1 hybrids and slightly deviate from expected Mendelian inheritance.  Microgametophyte certation of C. argyrosperma sororia may affect fertilization success of GM Cucurbita but transgenic hybrid progeny are still produced at a relatively high proportion.  The analysis of progeny vigor indicates that hyrbid transgenics germinate and produce the first true leaf at the same rate of the wild species, C. argyrosperma sororia.  Transgenic hybrids produced greater leaf area than the wild progenitor showing hybrid vigor.  Hybrids are also fertile and produce viable offspring