Drought severity and duration effects oat yield and yield components

Drought is a major constraint for oat ( Avena sativa L.) production, particularly during critical growth stages. Understanding genotypic responses to drought stress and identifying sensitive periods are essential for improving resilience. We evaluated the effects of drought severity and duration on two oat genotypes, Ajay and Hayden, under greenhouse conditions. Treatments were severe drought: 40% of water‐holding capacity (WHC); moderate drought: 60% of WHC; and well‐watered: ≥85% of WHC. Treatments were imposed during the heading, flowering, and grain filling stages until harvesting. Overall grain yield decreased by 23% and 41.5% under moderate and severe drought conditions, respectively, compared to the well‐watered condition. Hayden had higher grain yields, relative water content (RWC), and water use efficiency (WUE) than Ajay across all drought levels. Ajay showed higher root‐to‐shoot ratio, tiller number, and panicle number; however, these traits did not improve yield or leaf hydration under drought stress. Yield correlated strongly with yield components, such as panicle number and seed weight, compared to physiological traits, including soil plant analysis, development chlorophyll index, and RWC. Genotypes with high WUE and stable yields when exposed to drought during early reproductive stages should be prioritized in future research, which should directly measure performance under stress rather than rely on pre‐maturity physiological indicators.