The genome sizes of eight species from different wild population of diploid Medicago with origin from Algeria have been assessed by flow cytometry. This parameter vary from 2C=0.94 pg in Medicago orbicularis (the smallest genome) to 2C=1.80 pg in Medicago laciniata (the largest one). The relationship between genome size and competence for direct somatic embryo formation in liquid medium for four of the tested species (M. orbicularis Orbi DZ19 C 2C=0.94; M. truncatula Tru DZ 2B 2C=1.08; M.scutelata Scu 274 2C=1.11; M. arabica Ara 46 Ina 2C=1.22) was studied. It was found that Medicago orbicularis with the smallest genome size formed somatic embryos for a shortest period of time, with a high percent of reacting explants and number of somatic embryos per explant. It was followed by M. truncatula, M. scutelata and M. arabica.