Chromosome number and meiotic behaviour of two populations of Onobrychis chorassanica Bunge (O. sect. Hymenobrychis) in Iran

The genus Onobrychis belongs to family Fabaceae and has about 130 species throughout the world. Onobrychis sect. Hymenobrychis with nearly 14 species in Iran is one of the important sections of the genus. The chromosome number and meiotic behaviour were studied in two populations of Onobrychis chorassanica belonging to this section native to Iran. This report is the first cytogenetic analysis of this taxon. Both populations are diploid and possess 2n = 2x = 14 chromosome number, consistent with the proposed base number of x = 7. Although these taxa displayed regular bivalent pairing and chromosome segregation at meiosis, some meiotic abnormalities were observed. The meiotic abnormalities included varied degrees of chromosome stickiness including B-chromosome, cytomixis, asynchronous nucleus, fragmented chromosomes, occurrence of laggard chromosomes, chromosome bridges, desynapsis, micronucleous and tripolar cells.