Abstract

Increasing droughts due to global warming is compromising food security, particularly in Africa, where 95% of food production is rainfed. Tef, an orphan crop, is considered as future crop due to its drought adaptability and nutritional benefits. In Ethiopia, tef is a major source of nutrition for over half of the population. However, it loses viability when tissue water contents drop below 30% of that at full turgor. This study aimed to identify drought-tolerant tef genotypes and understand their mechanisms of tolerance. Twenty genotypes were evaluated in the field under both optimal (NS) and moisture-stressed (ST) conditions to assess their responses to terminal drought. Significant differences among genotypes were observed for most of the traits in both conditions, demonstrating a diverse response to moisture stress. Drought led to reductions in assimilation (A), transpiration (E), and stomatal conductance (gs), while increasing water use efficiency (WUE). Other physiological parameters such as NDVI and chlorophyll content, along with morphological traits, yield, and yield components were declined, except for the shoot-to-root ratio (SRR). Canopy temperature (CT) increased in both conditions but was more pronounced under ST, likely due to reduced gs, indicated by their negative correlation. There is a trade-off between low E and low CT. Low E is associated with drought resistance, while low CT is related to productivity and water use efficiency. Genotypes with high A and moderate E and gs exhibited higher WUE and productivity. Two main drought-resistance mechanisms were identified: drought escape, in high-yielding genotypes like Boni, and drought avoidance through reduced gs and increased root biomass, seen in several other genotypes. High-yielding genotypes such as Boni, Dtt2, and Enatite were characterized by early to intermediate maturity, moderate physiological and morphological characters, and high WUE. The study highlights the need of further research to uncover mechanisms of tolerance and subsequent omics studies are planned.

Key Words: Drought, Tef, Morphology, Physiology, Gas Exchange, Resistance Mechanisms