Studying Drought Tolerance in Thymus kotschyanus Accessions for Cultivation in Dryland Farming and Low Efficient Grassland

This study was carried out to evaluate drought stress tolerance in Thymus kotschyanus accessions using a factorial experiment based on a Completely Randomized Design (CRD) with 5 replications during 2013-2014 in Qom, Iran. The first factor was the accession with 17 levels and the second factor was drought stress with three levels of irrigation including 80% (control), 60% and 40% Field Capacity (FC). Data were collected for shoot length, root length, root to shoot length ratio (R/S), shoot fresh yield, oil percent, oil production and Relative Water Content (RWC). Result of analysis of variance showed significant differences between accessions, irrigation and accessions by irrigation interaction for all of traits (p<0.01). Results of means comparison showed that by increasing drought stress, the shoot length, shoot weight and RWC were decreased. For root length, R/S, oil content and oil yield, higher mean values were obtained in drought stress. Higher shoot weight, oil yield and oil content were obtained in moderate stress (60% FC). Results showed that accessions 29 and 50 (Abhar) for shoot length, accessions 29 and 10 (Uremia) for root length, accessions 29 and 47 (Lorestan) for shoot weight, accessions 29 and 5 (Alamoot) for oil yield and accessions 29 and 10 (Uremia) for oil content had significantly higher values in moderate irrigation (60%FC) than others and ranked in class a. For root length, and shoot weight, the accession 23 (Divandare) and for R/S, the accessions 22 (Abyek) and 10 had higher mean values in severe irrigation (40% FC) than others. Thymus kotschyanus accessions showed a high variation for drought tolerance in greenhouse conditions and this species is semi-tolerant to drought stress. Accessions Qazvin 2, Abyek, Uremia and unknown had higher oil productions than others. Therefore, these accessions can be used for cultivation in irrigation deficit and Lowyielding pastures.