Gene flow between cultivated and wild sunflowers

Abstract

With the development of transgenic crops, concern has been expressed regarding the possible escape of genetically-engineered genes via hybridization with wild relatives. This is a potential hazard for sunflowers because wild sunflowers occur as weeds in fields where cultivated sunflowers are grown and hybridization between them has been reported. In order to quantify the potential for gene escape, two experimental stands of sunflower cultivars were planted at two sites with different rainfall and altitude profiles. Populations of wild plants were planted at different distances from each cultivar stand. An allele homozygous in the cultivar (6Pgd-3-a), but absent in the wild populations, was used as a molecular marker to document the incidence and rate of gene escape from the cultivar into the wild populations of sunflowers. Three-thousand achenes were surveyed to determine the amount of gene flow from the cultivated to the wild populations. The marginal wild populations (3 m from the cultivar) showed the highest percentage (27%) of gene flow. Gene flow was found to decrease with distance; however, gene flow occurred up to distances of 1000 m from the source population. These data suggest that physical distance alone will be unlikely to prevent gene flow between cultivated and wild populations of sunflowers.

Gene flow from wheat (Triticum aestivum L.) to jointed goatgrass (Aegilops cylindrica Host.), as revealed by RAPD and microsatellite markers

“…the capacity of hybridization and the fertility of the hybrids and successive backcrosses, has to be investigated. The possibility of hybridization with a wild relative and the subsequent persistence of crop genes in the wild species have already been demonstrated for several crops; for example sunflower (Arias and Rieseberg 1994;Whitton et al 1998), sorghum Ellstrand 1996, 1997), radish (Lee and Snow 1998) and alfalfa (Jenczewski et al 1999).…”

CMS Lines for Evaluation of Pollen Flow in Sunflower Relevance for Transgene flow Mitigation

“…A number of studies documented the introgression and persistence of cultivar alleles in wild relatives (1,8,9,14,17). Several factors assist exchange of genes between wild and cultivated sunflowers: overlapping of flowering time, shared pollinators, self-incompatibility of wild sunflower, self compatibility of domesticated sunflower, and high rate of outcrossing.…”

“…The evidence for long distance pollen flow was obtained in other studies. Arias and Rieseberg (1) found that pollen from cultivated sunflower can be spread over a distance of 1 km and to pollinate the wild sunflowers. Pollen flow at long distances was also observed in canola (Brassica napus), which is pollinated by wind and insects.…”

Genetic variation among wild and cultivatedAgropyron desertorumpopulations based on total protein profiles and phenotypic traits

“…Early studies mainly focused on gene flow into crop strains because of fears that seed lots would be contaminated by foreign germplasm (Sprague 1938;Crane & Mather 1943;Haskell 1943;Bateman, 1947a, b, c;Jones 1948;Hutchcroft 1955;Nieuwhof 1963). More recently, concern has been expressed regarding gene flow from crop plants into their wild relatives via hybridization (Arias & Rieseberg 1994).…”