Introduction of Thymus daenensis into cultivation: Analysis of agro-morphological, phytochemical and genetic diversity of cultivated clones

Thymus daenensis Celak is an endemic and thymol rich species growing in Iran. Due to the extensive use of thymol in the pharmaceutical, food, feed, as well as in the livestock and poultry industry, T. daenensis has recently been introduced into cultivation. In this study, morphological, phytochemical and ISSR markers were applied to evaluate the genetic diversity and relationships among 59 cultivated T. daenensis clones. Among agromorphological traits, leaflet width (CV = 78.29) and drug yield (54.85%) had the maximum coefficient of variation. In addition, ranges of essential oil and thymol content varied from 3.26% (TD26) to 7.31% (TD181) and 48.11% (TD44) to 84.39% (TD10), respectively. Cluster analysis of 59 clones based on morphological and phytochemical data represented 3 main groups. ISSR primers reproduced a total of 103 polymorphic bands with an average of 8.58 bands per primer. Marker index varied from 1.64 (IS21) to 3.24 (IS04) with an average of 2.37. The UPGMA dendrogram acquired from the ISSR markers illustrated high variation between the studied clones and placed them into two main groups and different subgroups. Multiple regression analysis (MRA) was applied to estimate the relationships between morphological/phytochemical traits with ISSR bands. Five markers were diagnosed to be affiliated with thymol while three markers showed association with oil content. Also, several ISSR fragments showed association with some morphological traits. Outstanding diversity in terms of genetic, agro-morphological and phytochemical characteristics, gives to breeder the capability of selection and cultivation of the clones according to the purpose of breeding.