Karyotypic Studies of Two Thymus Species

Thymus kotschyanus and Thymus pubescence are 2 vast spreaded species of Thyme, growing all around the country in Iran. This study has characterized karyotypes of 4 populations of T. kotschyanus and 3 populations of T. pubescence all collected from their natural habitats. In other words, 2 ploidy levels were observed within the species and their chromosomes were mainly of m and the rest of sm type. Therefore, 2 data groups were formed for the 2 ploidy levels. Factorial analysis of variance was carried out on the data groups in completely randomized design model, regarding the populations and chromosomes of each group as the 2 factors. Total form percentage (TF%), and several other parameters were estimated to compare the karyotypes of the populations and the species. Analysis of variance presented significant differences between the diploid and tetraploid populations and their chromosomes, based on the data recorded on the karyotypes of the populations. Size of the chromosomes among the diploid populations of T. kotschyanus species varied from 0.92 to 2.06 μm. Chromosome length of the only diploid population of T. pubescence species varied from 1.05 to 2.32 μm. Within the 2 tetraploid populations of T. pubescence species the size of the chromosomes varied from 0.83 to 1.88 μm. Chromosome length of the only tetraploid population of T. kotschyanus species varied from 0.91 to 1.66 μm. In fact all of the chromosomes of the 2 species are very small in size. In average the chromosomes of tetraploid populations are smaller than the chromosomes of diploid populations.