A survey on chromosome counts of different sections belonging to the genus Trigonella L. (Fabaceae) throughout the world is presented and the relationships between chromosome data of its sections and their biogeography are also discussed here. In addition, chromosome numbers of 58 populations belonging to 19 species growing in Iran are reported. All studied species except T. monantha and T. orthoceras were diploid with chromosome number 2n = 2x = 16. T. monantha with four subspecies (2n = 4x = 28, 2n = 6x = 42) and T. orthoceras (2n = 6x = 48) were polyploid taxa. Based on the results, x = 7, 8 was determined for Trigonella genus. According to the chromosome and geographical data, Iran can be regarded as the center of origin of Trigonella genus.
