The study of morphology, meiotic behavior, chromosome number and pollen morphology of different populations of Onobrychis shahpurensis Rech. f. (O. sect. Onobrychis) was undertaken to evaluate and determine the variation and circumscription of this species in Iran. All populations were found to be diploid with 2n=2x=14, consistent with the previously proposed base number x=7 for the species. Almost all the populations displayed regular bivalent pairing and chromosome segregation at meiosis. However, some meiotic abnormalities were observed including various degrees of sticky chromosomes with laggards and bridges in anaphase to telophase, fragmented chromosomes in metaphase I, asynchronous nucleus in metaphase II and cytomixis. In addition, Onobrychis neychalanensis Ranjbar, Hadadi & Karamian, a new diploid species (2n=2x=14), belonging to the same section and morhologically similar to O. shahpurensis, but restricted to the northern Khalil‐Kuh mountain, northwest Iran, is described and illustrated.

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In this study, we describe the morphological characters and meiotic chromosome number and behavior of different wild populations belonging to Onobrychis viciifolia Scop., O. transcaucasica Grossh. and O. altissima Grossh. belonging to Onobrychis sect. Onobrychis in Iran. All Iranian populations of O. viciifolia and O. altissima studied here were tetraploid and showed 2n = 4x = 28 chromosome number, but O. transcaucasica populations were diploid. The basic chromosome number (x = 7) is consistent with the proposed base number for O. viciifolia and O. altissima from IPCN. For O. altissima, two ploidy levels (2n = 2x = 14 and 2n = 4x = 28) have been previously reported from Caucasus. The fact that no diploid populations of O. altissima were found in Iran, would suggest a relatively recent origin of the species, most probably in Caucasus.Although O. transcaucasica is diploid, its remarkable similarities in morphology to O. viciifolia and O. altissima can be suggested its relatively recent origin for these taxa. Almost all taxa studied here displayed regular bivalent pairing and chromosome segregation at meiosis. However, meiotic abnormalities observed included varied degree of sticky and fragmented chromosomes, laggards and bridges in anaphase to telophase, desynapsis in anaphase I and metaphase II, asynchronous nuclei and cytomixis.