Effect of planting date and salicylic acid on some quantitative and qualitative traits of quinoa as affected by drought stress

Introduction Quinoa (Chenopodium quinoa willd.) is an annual herbaceous plant belongs to Amaranthaceae family, but formerly placed in Chenopodiaceae family that originated in the Pacific slopes of the Andes in South America. It is cultivated in the world with an area of 126 thousand hectares with a production of 103 thousand tonnes. Determining the most suitable planting date means determining when plant growth and development are most consistent with climatic factors and the plant is less exposed to unfavorable environmental conditions. The management of planting date has the greatest impact on the phenological and growth characteristics of the plants compared to other treatments. Hirich et al. (2014) reported that 1st December (7.89 t ha-1) and 15th November (7.01 t ha-1) were found to record significantly higher dry matter production of quinoa than 15th March date of sowing among ten dates of sowing at an interval of 15 days from 1st November to 15th March. Reducing water resources for agricultural production is one of the main concerns of planners in most countries, especially in dry and semi-arid regions. Quinoa has been introduced as a drought tolerant and salinity resistant plant. One of the most important drought-tolerant mechanisms of the plant is the flexibility of the phenology and plant growth cycle when exposed to drought stress. Salicylic acid (SA) is a phenolic compound involved in the regulation of growth and development of plants, and their responses to biotic and abiotic stress factors. The objectives of this research were to determine the most suitable planting date of Quinoa in Bardsir, determine the optimal irrigation requirement, and investigate the role of salicylic acid in Quinoa resistance to drought stress. Materials and methods This study was conducted as split-split-plot based on randomized complete block design with three replications at experiment station of the Agricultural Faculty of Bardsir, Shahid Bahonar University of Kerman at 2018. The experimental treatments were planting date (5 April, 5 May and 5 June) assigned to main plot, irrigation levels (90%, 60% and 30% of filed capacity) as subplot and foliar application (salicylic acid 1 mM and water) as sub-subplot. Data were subjected to two-way analysis of variance (ANOVA) and the difference between treatment means was separated using LSD test. A significance level of 95% was applied by SAS 9.2. Results and discussion The results showed that the delay in planting date shortened the Quinoa growth period. GDD and growth period were decreased by drought stress. May planting date has significantly higher root length (31.81 cm) and dry weight (9.09 g plant-1) than two other planting dates. The highest root length for April (28.27 cm) and May (35.92) planting dates was assigned at 60% of FC, while for June (21.27 cm) was related to no-stress condition. Averagely, seed yield for May (653.91 kg ha-1) planting date was significantly higher than April (578.7 kg ha-1) and June (460.8 kg ha-1). Decrease in consumed water to 60% of FC had no significant effect on seed yield, but the trait value in 30% of FC was significantly lower than other irrigation levels. Justly at severe drought level, seed yield was significantly increased by foliar application of salicylic acid than water application. Relationship of seed yield was positive with seed oil percentage (r = 0.82) and was negative with protein percentage (r = -0.78). Water use efficiency (WUE) was significantly higher in May planting date than in April and June planting date. WUE increased significantly with water consumption decreasing. Conclusion Generally, the results illustrated that May planting date is the most suitable planting date for Quinoa in Bardsir regions and same climates. Results showed that the plant has a considerable tolerate in water stress condition. Salicylic acid could mitigate the negative impacts of drought stress in limited irrigation levels.