Biochemical traits and yield response of quinoa cultivars to salicylic acid foliar application under terminal heat stress

Background and objectives: Quinoa is a cereal-like plant with high nutritional value. Quinoa seeds are a rich source of protein, iron, magnesium, phosphorus, fiber and vitamin B2 and have a balanced content of essential amino acids for humans. Climate change, soil salinity and high tolerance of quinoa to abiotic stresses have made this plant a suitable option for sustainable agriculture. Therefore, knowing the appropriate sowing date of this plant is important in order to maximize plant growth and crop yield. On the other hand, salicylic acid is a plant growth regulator that is used to deal with various environmental stresses. For this purpose, this experiment was designed to investigate the yield and some biochemical indices of quinoa under the influence of sowing date and foliar spraying with salicylic acid.
Materials and Methods: This experiment carried out in the crop year 2021-2022, in the form of split split plots in a randomised complete block design with three replications in the research farm of the Faculty of Agriculture, Shahid Chamran University of Ahvaz. In this experiment, three factors were investigated: a) sowing date including October 12, November 11, and December 11 as the main factor, b) foliar application of salicylic acid at three levels including no application, 1.5 mM and 3 mM as a sub-factor, and c) quinoa cultivars including Titicaca, Giza and Redcarin as a sub-sub-factor.
Results: The results of the variance analysis of traits showed a significant difference in the interaction effect of sowing date × salicylic acid foliar application × cultivar in all studied traits. The application of 3 mM salicylic acid on the sowing date of October 12 in the Redcarin cultivar resulted in the highest grain yield. The highest activity of antioxidant enzymes, superoxide dismutase, proxidase and catalase, was obtained in the treatment of 3 mM salicylic acid on the sowing date of December 11. The lowest malondialdehyde content also belonged to the treatment of 3 mM salicylic acid on the sowing date of October 12 in the Redcarin cultivar. The treatment of 3 mM salicylic acid on the sowing date of October 12 in the Giza cultivar showed the highest starch content.
Conclusion: According to the results of this study, the application of 3 mM salicylic acid on the planting date of October 12 in the Redcarin cultivar resulted in the highest grain yield, therefore, the cultivation of this plant (Redcarin cultivar) on the planting date of October 12 was evaluated as the superior treatment due to the provision of better growth and development conditions and the application of 3 mM salicylic acid with the aim of improving photosynthetic characteristics, in order to achieve the practical goals of cultivating this plant. Of course, it should be noted that considering the complete confrontation of plant cultivation with environmental and climatic conditions and the lack of sufficient time to prepare the land after the previous crop in some agricultural lands, the choice of a second planting date (November 11) may also be unavoidable.