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Logo of bmcpsBioMed Centralsearchsubmit a manuscriptregisterthis articleBMC Plant Biology
 
BMC Plant Biol. 2012; 12: 43.
Published online Mar 26, 2012. doi:  10.1186/1471-2229-12-43
PMCID: PMC3384248
Crop to wild introgression in lettuce: following the fate of crop genome segments in backcross populations
Brigitte Uwimana,1 Marinus JM Smulders,2 Danny AP Hooftman,3 Yorike Hartman,4 Peter H van Tienderen,4 Johannes Jansen,5 Leah K McHale,6 Richard W Michelmore,7 Richard GF Visser,1 and Clemens CM van de Wielcorresponding author2
1Wageningen UR Plant Breeding, Postbus 386, 6700AJ Wageningen, the Netherlands
2Wageningen UR Plant Breeding, Postbus 16, 6700AA Wageningen, the Netherlands
3Centre for Ecology & Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK
4Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Postbus 94248, 1090 GE Amsterdam, the Netherlands
5Wageningen UR Plant Biometris, Postbus 100, 6700AC Wageningen, the Netherlands
6Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH 43210, USA
7Genome Center and Department of Plant Sciences, University of California Davis, Davis, CA 95616-8816, USA
corresponding authorCorresponding author.
Brigitte Uwimana: brigumbu/at/gmail.com; Marinus JM Smulders: rene.smulders/at/wur.nl; Danny AP Hooftman: Dann1/at/ceh.ac.uk; Yorike Hartman: Y.Hartman/at/uva.nl; Peter H van Tienderen: p.h.vantienderen/at/uva.nl; Johannes Jansen: johannes.jansen/at/wur.nl; Leah K McHale: mchale.21/at/osu.edu; Richard W Michelmore: rwmichelmore/at/ucdavis.edu; Richard GF Visser: richard.visser/at/wur.nl; Clemens CM van de Wiel: clemens.vandewiel/at/wur.nl
Received December 18, 2011; Accepted March 26, 2012.
Abstract
Background
After crop-wild hybridization, some of the crop genomic segments may become established in wild populations through selfing of the hybrids or through backcrosses to the wild parent. This constitutes a possible route through which crop (trans)genes could become established in natural populations. The likelihood of introgression of transgenes will not only be determined by fitness effects from the transgene itself but also by the crop genes linked to it. Although lettuce is generally regarded as self-pollinating, outbreeding does occur at a low frequency. Backcrossing to wild lettuce is a likely pathway to introgression along with selfing, due to the high frequency of wild individuals relative to the rarely occurring crop-wild hybrids. To test the effect of backcrossing on the vigour of inter-specific hybrids, Lactuca serriola, the closest wild relative of cultivated lettuce, was crossed with L. sativa and the F1 hybrid was backcrossed to L. serriola to generate BC1 and BC2 populations. Experiments were conducted on progeny from selfed plants of the backcrossing families (BC1S1 and BC2S1). Plant vigour of these two backcrossing populations was determined in the greenhouse under non-stress and abiotic stress conditions (salinity, drought, and nutrient deficiency).
Results
Despite the decreasing contribution of crop genomic blocks in the backcross populations, the BC1S1 and BC2S1 hybrids were characterized by a substantial genetic variation under both non-stress and stress conditions. Hybrids were identified that performed equally or better than the wild genotypes, indicating that two backcrossing events did not eliminate the effect of the crop genomic segments that contributed to the vigour of the BC1 and BC2 hybrids. QTLs for plant vigour under non-stress and the various stress conditions were detected in the two populations with positive as well as negative effects from the crop.
Conclusion
As it was shown that the crop contributed QTLs with either a positive or a negative effect on plant vigour, we hypothesize that genomic regions exist where transgenes could preferentially be located in order to mitigate their persistence in natural populations through genetic hitchhiking.
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