Sustainable enhancement of drought tolerance and oil traits in quinoa using mycorrhizal and seaweed biostimulants

Chenopodium quinoa Willd, known for its high tolerance to environmental stresses and significant nutritional value, is considered a strategic crop in arid regions. In light of climate change and increasing drought stress, this study evaluated the effects of three irrigation regimes—full irrigation, drought stress imposed at flowering, and drought stress imposed at grain filling—along with four biotic treatments; control, inoculation with arbuscular mycorrhizal fungi (AMF), foliar application of seaweed extract, and the combined application of both, on physiological traits, biochemical indices, yield, and oil quality of quinoa. The experiments were carried out at a research farm located in Ilam, Iran, from 2022 to 2024. Results showed that drought stress, particularly at flowering, significantly decreased chlorophyll a by 28.1 % and chlorophyll b by 26.7 %, nitrogen uptake by 32.8 %, phosphorus uptake by 36.4 %, potassium uptake by 43.7 %, and grain oil yield by 50.1 %, while electrolyte leakage (EL) and malondialdehyde (MDA) accumulation increased by 178.6 % and 89.9 %, respectively. Conversely, the combined AMF and seaweed extract treatment mitigated these adverse effects more effectively than individual applications. This treatment enhanced the activities of catalase, ascorbate peroxidase, and glutathione reductase by 185.6 %, 212.9 %, and 592.4 %, respectively, reduced MDA and EL by 80.5 % and 60.9 %, and improved nitrogen, phosphorus, and potassium uptake by 128.1 %, 142.6 %, and 181.8 %, respectively. It also increased phenolic and flavonoid contents by 37.6 and 44.2 %, ultimately enhancing thousand-grain weight by 79.1 % and grain yield by 155.3 %. Moreover, this combined treatment increased oil content by 52.7 % and oil yield by 288.3 %, elevated linolenic and linoleic acid concentrations by 109.7 and 38.1 %, and decreased palmitic and stearic acids levels by 41.3, 45.8 %, thereby improving both the quantity and quality of quinoa oil. Therefore, the simultaneous use of AMF inoculation and seaweed extract represents an effective, sustainable, and eco-friendly strategy to enhance quinoa’s drought tolerance. This approach holds great potential for improving sustainable production and food security, especially under climate change and water scarcity conditions.