Fourteen populations of Sections Hymenobrychis, Lophobrychis and Onobrychis of sainfoin were collected from natural habitats across Iran. Number and size of chromosomes as well as karyotypic formula of the populations were measured and studied using their root tip meristemes. The basic chromosome number varied between x=7 and x=8 and their chromosomal types were metacentric and sub-metacentric. According to average of genoms length, the highest belonged to O. viciaefolia (48.157µm) and the lowest to O. amoana subsp. meshhedensis (14.409µm). The results of analysis of variance based on unbalanced completely randomized design showed significant differences among the populations for the most of the studied traits (P<%1). O. michauxii2 classified as asymmetric class of B and others as A. O. amoena subsp. meshhedensis with 14m formula, stand in A class, had the most relative length of shortest chromosome(68.26), lowest intra chromosal asymmetrical(0.12) lowest differences of relative length(5.31) and the highest total form percentage was symmetrical species. Using principal components analysis, the first two components justified %97.94 of total variance. By cutting dendrogram, resulted from cluster analysis based on the karyptipic parameters species, the highest distance was obtained between O. schahuensis 1 and O. viciaefolia and the lowest metric distance value was obtained between populations of O. schahuensis 1 and O. chorassanica 1.
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