Abstract
Gene flow between domesticated species and their wild relatives is receiving growing attention. This study addressed introgression between wheat and natural populations of its wild relatives (Aegilops species). The sampling included 472 individuals, collected from 32 Mediterranean populations of three widespread Aegilops species (Aegilops geniculata, Ae. neglecta and Ae. triuncialis) and compared wheat field borders to areas isolated from agriculture. Individuals were characterized with amplified fragment length polymorphism fingerprinting, analysed through two computational approaches (i.e. Bayesian estimations of admixture and fuzzy clustering), and sequences marking wheat-specific insertions of transposable elements. With this combined approach, we detected substantial gene flow between wheat and Aegilops species. Specifically, Ae. neglecta and Ae. triuncialis showed significantly more admixed individuals close to wheat fields than in locations isolated from agriculture. In contrast, little evidence of gene flow was found in Ae. geniculata. Our results indicated that reproductive barriers have been regularly bypassed during the long history of sympatry between wheat and Aegilops.
Highlights
Many domesticated plants hybridize and backcross spontaneously with their wild relatives, and the potential for gene exchanges involving crop species is receiving growing attention since the last decade (Ellstrand et al 1999; Felber et al 2007)
Crop-to-wild gene flow has important evolutionary consequences for local relatives, as it can promote the origin of highly competitive genotypes that can develop into aggressive weed populations (e.g. Beta vulgaris · B. maritima hybrids, Ellstrand et al 1999; Amaranthus tuberculatus · A. hybridus, Trucco et al 2009)
We considered all populations located along cultivated fields, irrespectively of the crop being grown, as the presence of wheat could not be excluded during the preceding years because of culture rotations
Summary
Many domesticated plants hybridize and backcross spontaneously with their wild relatives, and the potential for gene exchanges involving crop species is receiving growing attention since the last decade (Ellstrand et al 1999; Felber et al 2007). Durum wheat (Triticum turgidum) is an allotetraploid crop species (2n = 4x = 28; genome BA, see van Slageren 1994 for genome nomenclature), with seven sets of chromosomes originating from Triticum urartu (A genome) and Ae. speltoides (B genome) (Waines and Barnhart 1992). It is mainly grown under semi-arid climates in western Asia, southern Europe and North America for pasta and semolina production. Aegilops species occur in open habitats, such as cultivation edges, roadsides, pastures, orchards or olives groves, and show a 2011 Blackwell Publishing Ltd 4 (2011) 685–695
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