Physiological and Agronomic Responses of Tef (Eragrostis tef [Zucc.] Trotter) to Terminal Drought Stress

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Abstract
Global warming has intensified drought episodes worldwide, with Africa experiencing pronounced impacts due to its reliance on rain-fed agriculture. This study investigated drought responses in tef (Eragrostis tef [Zucc.] Trotter) with the aim of identifying drought-tolerant genotypes and their underlying adaptive mechanisms. Tef is more resilient to drought than wheat, maize and rice but substantially affected by prolonged moisture scarcity. Twenty tef genotypes were evaluated under optimal and drought-stress conditions. Drought stress at the booting stage, followed by rehydration, significantly reduced soil and leaf water content, resulting in delayed maturity and substantial effect on agronomic and physiological traits. However, pronounced genotypic variation was observed. Drought-tolerant genotypes (For e.g RIL 44) exhibited smaller reductions in agronomic traits and demonstrated adaptive strategies, including early maturity and rapid recovery of normalized difference vegetation index and chlorophyll content (determined by SPAD), which collectively contributed to the maintenance of grain yield and shoot biomass under drought conditions. However, higher grain yield was not always associated with larger biomass, likely due to genotypic differences in biomass partitioning efficiency. Furthermore, genotypic differences were observed in responses to dehydration alone, and to rehydration following dehydration, indicating that most genotypes possess specific adaptations to either stress phase. These findings highlight the importance of evaluating combined drought and recovery responses and suggest that integrated stress screening could improve the identification of genotypes and mechanisms that enhance resilience to climate variability, particularly under conditions of erratic and reduced rainfall. We propose that root architectural studies conducted under field conditions across multiple environments and growing seasons would enhance the practical applicability of these findings for the development of drought-resilient tef genotypes.

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