Effect of Planting Date and Moisture Levels on Some Physiological and Biochemical Traits of Quinoa Cultivars (Chenopodium quinoa Willd.) in Birjand and Sarbisheh Regions

IntroductionThe economic importance of quinoa is not only due to the possibility of using the seeds as a food product characterized by a similar composition and use as consumer cereals but the species can also be managed as a leafy vegetable with high nutritional value and similar uses, such as, for example, spinach. Drought is another environmental stressor for plants subjected to severe water stress, especially in semi-arid and arid environments. Water scarcity poses a considerable challenge to crop production, leading to a notable reduction in crop yield. Quinoa, however, boasts low water requirements and demonstrates resilience in drought conditions. Even during dry periods, quinoa can effectively sustain leaf area and regulate photosynthetic activity. This resilience is facilitated by structural characteristics such as small, thin-walled cells, tissue flexibility, low osmotic potential, and controlled leaf area reduction through dehiscence. Other quinoa features for sustaining turgor pressure through osmotic adjustment during drought stress include inorganic ion buildup (e.g., Ca, K, and Na) and improved organic element synthesis (carotenoids and proline). Quinoa genotypes have several drought-resistance mechanisms, enabling this crop to grow and develop under severe drought conditions. Materials and MethodsTo evaluate the effect of moisture levels on some quinoa cultivars biochemical traits, four separate experiments were conducted in a factorial layout based on randomized complete block design with three replications in two regions (Birjand and Sarbisheh) and two planting dates (March and July/August) in 2018-2019. The experimental factors included five moisture levels (25, 50, 75, 100, and 125% of crop water requirement) and three quinoa cultivars (Titicaca, Giza1, and Redcarina). Some quinoa physiological and biochemical traits were evaluated by composite analysis at the 50% flowering stage and the effects of planting date and location were considered fixed.Results and DiscussionThe results showed that in August/July cultivation, the characteristics of RWC, electrolyte leakage, sodium percentage, potassium percentage, chlorophyll a, carotenoids, proline content, and total soluble carbohydrate of leaves were increased by 17.10, 74.62, 95.51, 31.9, 3.53, 38.65, 94.19 and 9.30% respectively and chlorophyll b content decreased by 13.15% compared to March culture. Also, in Sarbisheh, RWC, electrolyte leakage, potassium percentage, and leaf carotenoids are respectively 3.53, 38.65, 94.19 and 9.30% more than Birjand, but sodium percentage, chlorophyll a, chlorophyll b, proline and total soluble carbohydrates of leaves were 4, 1.88, 15.67, 51.02 and 30.41% less than Birjand, respectively. In most of the studied traits, the Giza1 cultivar had higher quality traits. Severe water scarcity resulted in an elevation of certain biochemical traits in quinoa leaves. Specifically, as moisture levels decreased from 125% to 25% of the water requirement, there was a significant increase in electrolyte leakage, sodium and potassium percentages, chlorophyll a and b, carotenoids, proline, and total leaf soluble carbohydrates by 24.50%, 37.84%, 35.89%, 24.83%, 59.12%, 48.75%, 51.58%, and 36.71%, respectively. However, the relative water content (RWC) decreased by 17.70%. Notably, there were no significant differences observed between the 125% and 100% levels of water requirement for most of the analyzed traits.ConclusionIn general, with the significance of the triple interaction of planting date × location × cultivar, as a result, the reaction of each variety depends on the planting date and location of its planting. But in general, most of the quinoa leaf physiological and biochemical traits increased in August/July cultivation. In Birjand, due to the higher average temperature and other climatic parameters compared to Sarbisheh, and probably understanding the heat stress, traits such as photosynthetic pigments, proline, and soluble carbohydrates had higher values. In this research, the Giza1 was superior to the other two cultivars, and moisture stress caused a significant decrease in the water content of the leaves and a significant increase in quinoa leaves quality traits.