Three-Step Screening for Salinity Tolerance in Ajowan (Trachyspermum ammi L.) Sprague ex Turrill)

Ajowan is an important medicinal plant that grows mainly in arid and semi-arid regions of the world. To evaluate salinity tolerance of 25 Iranian ajowan ecotypes, three-step screening was conducted at germination, seedling, and adult plant growth stages using 0, 50, 100 and 150 mM of NaCl. The significant effects of salinity were observed at the three studied growth stages of ajowan ecotypes. Germination percentage, seed vigor, and biomass dry weight of investigated ecotypes decreased with the increase in NaCl levels. Different responses were observed among ajowan ecotypes in terms of activity of antioxidant enzymes of catalase and peroxidase, with the increasing salinity stress levels .Under the salinity stress, the proline content increased in the majority of the investigated ecotypes. Salinity stress had adverse effects on single plant seed yield and yield components. Results of the calculated correlation coefficient and path coefficient analysis showed that activity of catalase antioxidant enzyme and 1,000-seed weight were the most important characteristics that can be suggested as selection criteria for seed yield of ajowan under salinity stress conditions. The overall results suggest that nine Iranian ajowan ecotypes including Arak, Felaverjan, Ghoom, Hamedan, Karaj, Ghaen, Tehran, Yazd, and Shiraz were the salinity-tolerant ecotypes.