Evaluation the effect of salinity stress on the protein and micronutrient elements content of quinoa seeds

Introduction: Quinoa (Chenopodium quinoa Willd) belongs to the Amaranth family and is native to the Andes. In recent decades, the cultivation of this plant has extended. One of the reasons for paying attention to this plant is its ability to adapt to harsh climatic conditions. It has a higher protein content than wheat, barley, corn and rice. On the other hand, plant seeds supply all the essential amino acids (including lysine, methionine and cysteine) needed by humans. The aim of this experiment was to investigate the effect of salinity stress on the amount of micronutrients and protein percentage in quinoa seeds.
Material and Methods: An experiment was planted as a split plot in a randomized complete block design with three replications on August 7, 2017. Experimental treatments included three superior genotypes (Sadough, Titicaca and NSRCQB). Genotype in sub-plot and irrigation water salinity at 3 levels of 2, 10 and 17 dS/m were located in the main plot. Finally, grain yield, saponin content (foam height), grain size and amount of micronutrients in grain and grain protein percentage were measured after saponification.
Results: The effect of salinity stress on 1000-grain weight, grain yield, grain size (1.7-2, 1.4-1.7 mm), foam height, iron, zinc, calcium content and protein yield were significant. Sadough cultivar had the highest 1000-seed weight and grain yield. Sadough and Titicaca cultivar had the highest percentage of large seeds and small seeds, respectively. With increasing salinity, seed yield of Titicaca cultivar decreased by 13% per unit increasing irrigation water salinity, while in Sadough and NSRCQB genotypes, there was no significant difference with non-saline level. With increasing salinity, the lowest foam height was related to NSRCQB genotype. The interaction effect of salinity stress and genotype on grain yield, foam height, percentage of iron, zinc, calcium, protein and protein yield was significant. With increasing salinity, iron content in Titicaca cultivar, zinc content in all three genotypes, nitrogen in Sadough and NSRCQB, calcium in Titicaca, protein percentage in Sadough and NSRCQB increased significantly compared to non-saline conditions. With increasing salinity, the highest increase slope among micronutrients was related to grain. Protein yield in Sadough and NSRCQB cultivars was not affected by salinity increase, while in Titicaca cultivar decreased by 13% per unit of irrigation water salinity.
Conclusion: With increasing salinity up to 10 dS/m, the seed yield of three quinoa genotypes was not affected and this plant is recommended for exploitation of saline water resources. Sadough cultivar was the best among the three genotypes. The percentage of micronutrients iron, calcium, zinc and grain protein increased under saline conditions and despite the decrease in grain yield, the protein yield per square meter was not affected. The rate of increase in micronutrients and decrease in yield with increasing salinity of irrigation water is affected by genotype. Since the quantity and quality of quinoa seeds are not affected by water salinity, it can be effective in improving food security in marginal areas.