The medicinal plants have been used for human health and have different pharmaceutical and industrial applications. Yarrow ( Achillea ) is a perennial plant species from composite family with different medicinal and ornamental uses. Salt stress is considered as one of the most crucial problem in arid and semi-arid regions of the world. The present study was conducted to assess the effect of salt stress on morpho-phenological, physiological and phytochemical properties and selecting of the best genotypes in respect to salt tolerance and high yield in 10 genotypes of Achillea belonging to seven species. The genotypes included A. millefolium (Hamedan, Orumieh, Kandovan), A. filipendulina (California, Ardebil), A. santolina (Shahrekord), A. nobilis (Shandiz), A. aucherii (Gachsar), A. pachycephalla (Golestan) and A.tenuifolia (Golestan). The genotypes were evaluated in a factorial experiment in a complete random design (CRD) in four levels of salinity treatments including control (tap water), 5, 10 and 15 dsm -1 . The results of analysis of variance showed significant differences among the populations for morphological traits in four salt stress regimes. Salt stress lead to decrease in plant height, leaf area, flower diameter and shoot dry weight, while it lead to increase the proline content, catalase and ascorbate peroxidase enzymes. It also elevated the total phenolic, flavonoid content and antioxidant activity. The highest plant height, chlorophyll, leaf area and dry weight were obtained in Hamedan, Orumieh and California in control, respectively. The highest amount of catalase, ascorbate peroxidase, phenolic and flavonoid content was observed in Shahrekord, California and Kandovan in 15dsm -1 , respectively. Cluster analysis divided the genotypes in three groups in 0 dsm -1 , four groups in 5 dsm -1 , and three groups in 10 dsm -1 while it Keywords : Yarrow, Salt stress, Secondary metabolites
