In order to study the effect of drought stress at budding stage on five black cumin (Nigella sativa L.) ecotypes (Arak, Yasuj, Semirom, Azarbaijan, and Torbat Heydarieh), an experiment was conducted in based on a factorial randomized complete block design (RCBD) with four replications in Islamic Azad University, Arak branch, Arak, Iran. Treatments included control (normal irrigation) and drought stress (stop irrigation at budding stage until the end of the growth period). Oil percentage, oleic acid, linoleic acid, and linolenic acid were affected by drought and the highest values of oil percentage (2.6%), oleic acid (0.27%), linoleic acid (13.02%) and linolenic acid (1.57%) were observed in Arak, Torbat Heydarieh, Yasuj, and Torbat Heydarieh ecotypes, respectively. Results of tolerance indices showed that Torbat Heydarieh had the highest value of GMP (233.8), STI (2.26), and SSI (84.64). The correlation analysis showed Yp with GMP (r=+0.89**), STI (r=+0.95**), and MP (r=+0.89**). Based on the present study, Torbat Heydarieh ecotype is recommended for planting in arid and semi-arid regions.
