1. ¹Plant Research Department, Risø National Laboratory, Roskilde, Denmark
2. ²Faculty of Life Sciences, Department of Ecology, University of Copenhagen, Frederiksberg, Denmark

Correspondence: Dr TP Hauser, Department of Ecology, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 21, DK-1958 Frederiksberg, Denmark. E-mail: tpha@life.ku.dk

Received 22 March 2006; Revised 23 March 2007; Accepted 26 March 2007; Published online 2 May 2007.

Abstract

Many cultivated plant species are able to hybridize with related wild plants. However, it is not clear whether their hybrids are able to survive and reproduce outside managed fields, and if cultivar genes introgress into wild populations. In areas where wild carrots co-occur with carrot root-crops, pollen and seeds may flow from two different sources in the fields to the surrounding wild populations: from pure cultivar plants that occasionally flower, and from flowering 'bolters' that originate from hybridizations between wild () and cultivated carrots () in seed production fields in warmer regions of the world. To test whether hybrids are formed and survive in wild Danish populations, and whether prolonged hybridization has led to introgression of cultivar genes, we collected leaf material from adult individuals growing close to carrot fields and analysed their genotypic composition by AFLP. Four hybrids were identified among the 71 plants analysed, and these were most likely F₂ or backcross individuals, sired by pollen from hybrid bolters. Wild populations close to fields were genetically somewhat more similar to cultivars than wild populations far from fields, suggesting that neutral or beneficial cultivar alleles can introgress into the wild gene pool. Despite generations of improvement and adaptation of cultivar carrots to highly managed field conditions, hybrids can thus sometimes survive in wild populations close to carrot fields, and their genes transfer to wild populations by introgression.