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 F 1hybrid was backcrossed to L. serriola to generate BC 1and BC 2populations. Experiments were conducted on progeny from selfed plants of the backcrossing families (BC 1S 1and BC 2S 1). 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 BC 1S 1and BC 2S 1hybrids 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 BC 1and BC 2hybrids. 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. © 2012 Uwimana et al; licensee BioMed Central Ltd.
Uwimana, B., Smulders, M. J. M., Hooftman, D. A. P., Hartman, Y., van Tienderen, P. H., Jansen, J., … van de Wiel, C. C. M. (2012). Crop to wild introgression in lettuce: Following the fate of crop genome segments in backcross populations. BMC Plant Biology, 12. https://doi.org/10.1186/1471-2229-12-43