Study of Isfahan Thymus daenensis accessions genetic diversity based on karyotypic characteristics

Thyme (Thymus vulgaris L.), is one of the most importantaromatic medicinal plants, which has widely distributedin the old World. The Mediterranean region can bedescribed as the centre of the genus. Thymus belongs toLamiaceae family and is grown mostly in Spain and Turkey[1]. Knowledge about genetic diversity among breedingmaterials could be an invaluable help in the strategies ofimprovement [2]. Since the 93% of wild medicinal plantsare in imminent danger of extinction, the present studyinvestigated genetic diversity in this herb using threeThymus sp. accessions collected from different regionsin Isfahan using karyotypic characteristics. Some traitsincluding TL, LA, SA, AR and CI were determined for eachaccession by using MicroMeasure software version 3.3,and some other traits includes %RL, %LA, %SA and %TFwere calculated for each accession by Excel software.Significant variation for some traits was observed amongaccessions by variance analysis. Karyotype studies forThymus genus showed that all three accessions Thymusdaenensis were diploid (2n=2x=30). Karyotype formulasof the accessions were 15m. According to Stebbinsclassification, all the accessions placed in the A1category[3]. Using principal components analysis, the first twocomponents determined %99.92 of the total variance. Inthe first component, total length, the length of long armand short arm of chromosome, with the highest eigenvectors were the most important traits. Centromereindex and the arm ratio had the most important role fortotal variation in the second component