Ferula assa-foetida is one of the most important medicinal, rangeland and industrial plants that, in addition to its role in soil protection, produces oleo-gum with high medicinal and industrial value. The present study aimed to evaluate karyotypic variation and cytogenetic diversity among natural populations of F. assa-foetida. For karyological analysis, eight populations of F. assa-foetida were collected from Fars Province, Iran. The results showed that all populations were diploid (۲n = ۲x = ۲۲), with a basic chromosomes number of x = ۱۱. Despite the uniform chromosome number, significant differences were observed among populations in terms of karyotypic and chromosomal characteristics. Regarding chromosome length (CL), long arm length (L) and short arm length (S) populations F۵ exhibited the largest chromosomes with the highest mean values, whereas population F۲ showed the smallest chromosomes with the lowest mean values. Based on intrachromosomal asymmetry parameters, F۵ displayed the most asymmetric karyotype with the highest mean A۱ and the lowest TF% values, while F۷ showed the most symmetric karyotype with the lowest mean A۱ and the highest TF% values. In terms of interchromosomal asymmetry indices, the highest mean values of A۲ and DRL were observed in F۷, whereas the lowest values were recorded in F۲. Most karyotypes were relatively symmetrical and classified within the ۱A and ۲A categories of Stebbins’ classification. Principal component analysis revealed that the first two components explained more than ۹۶.۳% of the total variation among populations. The first component was mainly associated with intrachromosomal symmetry parameters, whereas the second component was related to chromosome size and interchromosomal symmetry. Cluster analysis using the UPGMA method grouped the studied populations into two distinct clusters, indicating the presence of cytogenetic differentiation among populations. These results highlight that structural chromosomal variation, rather than changes in chromosome number, plays an important role in population differentiation of F. assa-foetida.
