Study on general combining ability of morphological and phytochemical traits in ‎different populations of Thymus daenensis in polycross test

Thymus daenensis, one of the endemic thyme in Iran, is very important in the pharmaceutical and food industries due to high percentage of essential oils and high levels of thymol in essential oils. In order to evaluate genetic parameters and general combining ability (GCA) in 12 populations of T. daenensis, a polycross design has been used. Polycross test in a randomized complete block design with 6 replications in 2014 and 2015, and polycross progeny test in a randomized complete block design with 3 replications in 2016 and 2017 were carried out in the Horticultural Department, University of Tehran. Karaj. Iran. Morphological traits, essential oil content and yield, thymol and carvacrol were evaluated. Results revealed that, the high level of GCA for important traits such as plant height, plant fresh and dry weight and leaf dry weight were obtained in populations of Ilam, Isfahan 2, Markazi 1 and Markazi 2 and for essential oil percentage and yield were obtained in populations of Ilam and Malayer 2. Overall, the results of this study indicated a high diversity for morphological and phytochemical traits in studied populations. Also, Ilam, Malayer 2, Markazi 1 and Markazi 2 populations with positive and high GCA provide good opportunities for creating synthetic varieties or new genetic source for selection of superior genotypes.