Introduction
Since plants cannot move, they face many environmental stresses. Salinity is a major threat to modern agriculture, causing inhibition and impairment of crop growth and development. Salinity stress affects all vital plant processes such as photosynthesis, protein and metabolism of fat in the plant, causing changes in morphological, physiological, biochemical and molecular functions of the plant, which ultimately decreases plant yield. Due to high nutritional value and high resistance to abiotic stresses such as salinity and drought, quinoa (Chenopodium quinoa willd.) has been proposed to ensure food security in the world. Quinoa genotypes have different morphological and physiological mechanisms in terms of germination, growth and grain yield under salinity stress. Considering the differences in salinity resistance in different quinoa cultivars, this study was carried out for investigating the physiological responses and seed yield of three quinoa cultivars with different origins under salinity stress.
 Materials and Methods
This experiment carried out as random complete block design with three replications in the greenhouse of the Faculty of Agriculture of Zanjan University during the year 2019. The experimental treatments included three salinity levels of 0, 15 and 30 dS m^-1 and three quinoa varieties (Giza1, Titicaca and Q26) with different origins. First, soil with a ratio of 50% sieved farm soil, 30% sand and 20% rotted manure was added inside the 1 kg pots. Inside each pot, 10 seeds were planted then irrigated with desired concentrations of salinity. The temperature of the greenhouse during the day was 27±2 and at night 19±2 ˚C, and the relative humidity was 65-75%. After the seedlings were fully established, four plants were kept in each pot and the rest were removed. The volume of irrigation water was 400 cc for each pot with the desired concentration of salinity. In the following, the desired traits were measured based on the mentioned protocols in specific stages. After measuring the desired traits, variance analysis of the data was done with SAS software version 9.1, comparison of average data was done using Duncan's multiple range test (P>0.05).
 Results and Discussion
Salinity stress had a significant effect on all the traits studied except the potassium concentration of the root. Salinity reduced the plant height, leaf area, greenness index, grain yield, dry weight shoot and root, but salinity caused increase in the amount of sodium in the root, stem and leaves. The highest and lowest grain yields, with 0.87 and 0.56 g plant^-1 were observed in the control and 30 dS m^-1 salinity treatments, respectively. The Titicaca cultivar with 25.7 cm, had the lowest plant height. The highest shoot dry weight, stem sodium concentration, Na⁺/K⁺ ratio in root and Na⁺/K⁺ ratio in stem were observed in the Giza 1 cultivar. The Q26 cultivar had highest height of plant (33.8 cm), leaf area (3865.8 cm²plant^-1), root sodium (0.30 mg.g^-1 dry weight) and potassium (0.16 mg.g^-1 dry weight) concentration, while it had the lowest Na+/K+ ratio in leaf with 0.67 mg.g^-1 dry weight. Traits such as leaf potassium concentration and grain yield were similar among the studied cultivars. Also, cultivar Q26 had the lowest Na⁺/K⁺ ratio in the leaves with 0.67 mg.g^-1 dry weight. The leaf greenness index in the control and salinity of 15 dS.m^-1 was the same among all studied cultivars, but in the salinity of 30 dS.m^-1, the Titicaca cultivar had the lowest amount. Among the studied cultivars, Giza 1 cultivar had the lowest root dry weight, while it had the highest Na⁺/K⁺ ratio in root and stem (8.27 and 3.6 mg.g^-1 dry weight, respectively) among all salinity treatments. The Titicaca cultivar had the highest stem potassium concentration of all salinity levels in studied cultivars.
 Conclusions
 The results obtained from this research showed that high salinity concentrations decreased the grain yield of quinoa. In general, the results showed that the cultivars examined in this research (Giza1, Titicaca and Q26) were different from each other in terms of traits related to salinity resistance. The results showed that the origin of cultivars probably plays a role in the resistance to salinity. Also, despite the difference in the concentration of elements potassium, sodium and Na⁺/K⁺ ratio in the stem, root and leaf organs, and no significant difference was observed in terms of grain yield among the studied cultivars. Therefore, it is suggested to consider their origin in the selection of cultivars for future research.