Abstract
<title>Abstract</title> <p> Quinoa ( <italic>Chenopodium quinoa</italic> Willd), a vital crop native to south America, holds potential for maximizing the use of Egyptian marginal lands in hot arid regions thanks to its broad genetic diversity and adaptability to harsh environmental conditions. yet the interaction between irrigation regime and genotype shaping agronomic performance remains poorly characterised. We analysed the performance of three genotypes (‘ICBA-Q3’, ‘ICBA-Q5’ and ‘Misr1’) against three irrigation schedules for two winter seasons field trial (2023–2024 and 2024–2025) under southern Mediterranean sandy soil conditions. A cohort of parameters were assessed in this experiment including canopy temperature, vegetative traits, yield components, and grain yield. Seasonal variation was significant for most traits, with 2024–2025 recording higher canopy temperatures and lower vegetative growth and yield, consistent with greater atmospheric evaporative demand during critical developmental stages. Irrigation regime significantly reduced branches and leaves by 16% and 23%, respectively, relative to well-watered condition. The Egyptian cultivar 'Misr1' consistently outperformed ICBA genotypes in vegetative vigour, grain yield (4.11 vs. 1.67 and 0.85 ton/ha), reflecting its adaptation to local conditions. However, the significant irrigation × genotype interaction revealed that 'Misr1', despite its superior yield potential, was more sensitive to water reduction, while ICBA genotypes sustained yield stability across irrigation treatments. Canopy temperature at mid-season was a reliable predictor of grain yield under full irrigation (r² = 0.63) but faded under water deficit, cautioning against its use as a selection criterion under drought. Thousand seed weight and harvest index were irrigation-insensitive, only genotype-driven traits. These findings insight genotype selection and irrigation management strategies for quinoa production on marginal lands in Mediterranean Egypt. </p>