Extensive introgressive hybridization between cultivated lucerne and the native sickle medic (Medicago sativa ssp falcata) in Estonia

Kaljund, K. & Leht, M. 2013: Extensive introgressive hybridization between cultivated lucerne and the native sickle medic (Medicago sativa ssp. falcata) in Estonia. - Ann. Bot Fennici 50: 23-31. We studied the occurrence of the crop-to-wild introgressive hybridization in the Medicago sativa-falcata complex in the distribution area of the native M. sativa ssp. falcata (hereafter falcata) in western and northern Estonia. Flower colour and pod shape were used as the diagnostic genetic characters to assess the extent of hybridization from cultivated lucerne to populations of falcata. Among the 106 populations examined, only 15 were pure yellow-flowered falcata populations. In the remaining 91 populations, 1%-90% of the plants had variegated flowers typical of hybrid plants, indicating widespread but highly variable introgression. Hybrid plants were detected most frequently in disturbed man-made habitats, mostly roadsides, wastelands and fallow fields. Hybrid plants with variegated flowers were found to have not only pod shapes characteristic of falcata but also coiled pods characteristic of cultivars, indicating that due to introgression hybrid populations have become morphologically more diverse.