Mehdi Moradi - Torbat-e Jam, College of Agriculture and Animal Science, Torbat-e Jam, Iran
Vahideh Nazeri - Department of Horticultural Sciences, Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
Mohammad Reza Hassandokht - Department of Horticultural Sciences, Faculty of Agriculture, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.

Karyotypes of five populations of Thymus transcaspicus from different geographic sites in Iran are presented. The basic chromosome number of the studied populations was obtained as x=۱۵. Presence of ۳۰ chromosomes in Tiwan, Hikooh, Pakotel and Golmakharan populations and ۶۰ chromosomes in Reiin population corresponds to diploid (۲n = ۲x = ۳۰) and tetraploid levels (۲n = ۴x = ۶۰), respectively. Chromosome number of ۲n= ۳۰ is reported for the first time in the species. Metacentric chromosomes are the most common, but sub-metacentric chromosomes are rare. Based on intrachromosomal asymmetry (A۱ and TF %), population Reiin had the most asymmetric karyotype and population Golmakharan had the most symmetrical karyotype among the populations. According to interchromosomal asymmetry (A۲ and DRL), among diploid populations, population Pakotal had the asymmetrical karyotype. The results indicate that at least in Iran T. transcaspicus is not a uniform species in regard to its chromosome number and karyotype. Meanwhile poloidy has played a role in the evolution within species.

Thymus, Lamiaceae, symetric karyotype, diversity, Cytology, Iran