Introduction: Salicornia is a genus of annual herbaceous halophytes belonging to the Amaranthaceae family. It is recognized as a significant genetic resource for its high tolerance to various environmental stresses, particularly salinity. For a long time, researchers globally have focused on this plant for its potential to produce edible oil, forage, seed meal, and leafy vegetables. Of the 25 to 30 known Salicornia species worldwide, seven are recorded in Iran's flora. The distribution of these species in Iran is directly related to their ecological requirements. Drought-tolerant species are primarily found in central Iran, while Salicornia persica, adapted to marshy and extremely high-salinity conditions, is distributed across the southern and central regions of the country. Interestingly, despite their ability to thrive in highly saline environments, the germination of Salicornia seeds is severely inhibited by high salt concentrations. Therefore, this study was conducted to evaluate the response of three native S. persica ecotypes to various levels of sodium chloride-induced salinity stress during the germination stage.

Materials and methods: The present study was conducted to determine the salinity tolerance threshold of three S. persica ecotypes during the germination stage. The experiment was designed as a factorial arrangement in a completely randomized design with three replicates. The experimental treatments included eight salinity levels: a control with distilled water and levels of 10, 20, 30, 40, 50, 60, and 70 dS m-1, prepared using sodium chloride from Merck, Germany. Three ecotypes of S. persica, namely, Central Plateau, Urmia, and Bushehr, sourced from the National Salt Research Center of Iran, were also used. The research was carried out at the Seed Technology Laboratory of the Department of Plant Production and Genetics, Faculty of Agriculture, Shahid Chamran University of Ahvaz.

Results and discussion: The results revealed that increasing salinity significantly affected the vital indices of germination and early seedling growth. In the Bushehr ecotype, the germination percentage dropped from 100% in the control to just 6% at a salinity of 70 dS m-1. Similarly, the decline was substantial for both the Urmia and Central Plateau ecotypes. Among all ecotypes, the Central Plateau demonstrated the highest tolerance to salinity. Furthermore, the estimation of the salinity tolerance threshold using a 3-parameter logistic model predicted the 50% reduction threshold for germination percentage to be 47.73, 43.95, and 37.67 dS m-1 for the Central Plateau, Urmia, and Bushehr ecotypes, respectively. Correspondingly, the 50% reduction threshold for the seed vigor index was calculated as 38.75, 29.78, and 22.90 dS m-1 for the same ecotypes. These findings clearly indicate that the seed vigor index is more sensitive to salinity stress than the germination percentage.

Conclusions: The findings of this study generally revealed that native ecotypes of S. persica possess significant genetic differences in their tolerance to salinity stress during the germination phase. At high salinity levels, key indicators such as germination percentage, germination rate, and particularly the seed vigor index, were severely impacted and showed a substantial decline. A comparison of the three examined ecotypes showed that the Central Plateau ecotype was the most salt-tolerant, exhibiting the highest tolerance threshold and the smallest reduction in germination indices. This superiority was evident not only under stress conditions but also in the absence of salinity. The use of a 3-parameter logistic model to estimate the critical 50% reduction threshold for both germination and seed vigor further validated this observation. Given the remarkable adaptability of the Central Plateau ecotype to saline environments, we recommend its use as a superior genetic resource for breeding programs and for expanding its cultivation in saline lands and coastal areas. This would enable the sustainable production of forage, edible oil, and other by-products in regions with limited access to freshwater.