THE PERSISTENCE OF CULTIVAR ALLELES IN WILD POPULATIONS OF SUNFLOWERS5 GENERATIONS AFTER HYBRIDIZATION

The development of transgenic plants has heightened concern about the possible escape of genetically engineered material into the wild. Hybr idization between crops and their wild relatives provides a mechanism by which this could occur. While hybridization has been documented bet ween several crops and wild or weedy relatives, little is known about the persistence of cultivar genes in wild populations in the generatio ns following hybridization. Wild and weedy sunflowers occur sympatrica lly with cultivated sunflowers throughout much of the cultivation rang e, and hybridization is known to occur. We surveyed two cultivar-speci fic RAPD markers in 2700 progeny in a naturally occurring population o f wild Helianthus annuus over five generations following a single gene ration of hybridization with the cultivar. Moderate levels of gene flo w were detected in the first generation (42% hybrids at the crop margi n) and cultivar allele frequencies did not significantly decline over four subsequent generations. These results indicate that gene flow fro m cultivated into wild populations of sunflowers can result in the lon g-term establishment of cultivar alleles in wild populations. Furtherm ore, we conclude that neutral or favorable transgenes have the potenti al to escape and persist in wild sunflower populations.