| Affiliation: | 1. Laboratoire de ressources ge´ne´tiques et d'ame´lioration des luzernes me´diterrane´ennes, Unite´ de Recherche deGe´ne´tique et Ame´lioration des Plantes, INRA Montpellier, Domaine de Melgueil, 34130 Mauguio, France Author for correspondence (tel: 334 67 29 06 19, fax: 334 67 29 39 90, e-mail: jenczewski@ensam.inra.fr).;2. Laboratoire de ressources ge´ne´tiques et d'ame´lioration des luzernes me´diterrane´ennes, Unite´ de Recherche deGe´ne´tique et Ame´lioration des Plantes, INRA Montpellier, Domaine de Melgueil, 34130 Mauguio, France |
| Abstract: | Genetic differentiation between co-occurring crops and their wild relatives will be greatly modified by crop-to-weed gene flow and variation between human and natural selective pressures. The maintenance of original morphological features in most natural populations of Medicago sativa in Spain questions the relative extent of these antagonistic forces. In this paper, we measured and compared the pattern of population differentiation within and among the wild and cultivated gene pool with respect to both allozymes and quantitative traits. Patterns of diversity defined three kinds of natural populations. First, some populations were intermediate with respect to both allozymes and quantitative traits. This suggests that crop-to-weed gene flow may have created hybrid populations in some locations. Second, some populations were different from all the cultivated landraces with respect to both allozymes and quantitative traits. This probably results from variable gene flow in space and in time, due to demographic stochasticity in either natural or cultivated populations. Third, differentiation from cultivated landraces was only achieved for the quantitative traits but not for allozymes in two populations. This suggests that natural selection in some locations may oppose gene flow to establish cultivated traits into the natural introgressed populations. |
