Study of Traits Related to Yield, Drought Tolerance, Summer Dormancy, and Post-Drought Recovery in Tall Fescue

This study was performed to investigate the effects of drought stress on agronomic traits, post-drought recovery, and survival of tall fescue genotypes in the Research Farm of the Isfahan University of Technology located in Lavark, Najafabad, central Iran. In this study, 67 tall fescue genotypes, including three groups of the early, medium, and late in terms of flowering were studied. All genotypes were fully irrigated after planting for two years (2016-2017) and then in the third and fourth years (2018-2019) were examined under three irrigation environments including normal water (50% moisture depletion) mild drought stress (70% moisture depletion), and intense drought stress (90% moisture depletion). Morphological and performance traits were examined. In the summer of the fourth year (2019) after the summer harvest, irrigation was stopped in all drought stress levels for two months. Then the plants were irrigated again for six weeks, and after regrowth, recovery-related traits were evaluated. High genetic diversity was observed among tall fescue genotypes for all measured traits. The results showed that drought stress had adverse effects on forage yield and yield components, recovery traits, and survival. Prolonged drought stress changed the relationships between different traits. Significant positive correlation between the forage yield and recovery rate with drought tolerance indicated that these traits could be used as appropriate selection criteria to increase forage yield and identify superior genotypes in arid and semi-arid regions. The results of this study indicated low to moderate summer dormancy (incomplete summer dormancy) in this germplasm. Negative correlation of functional and stress tolerance traits with day to recovery under drought stress conditions showed that drought tolerant genotypes will have faster recovery than other genotypes. The results showed that some late flowering genotypes (such as 3L, 18L and 11L) are valuable gene sources for forage production. Drought tolerant genotypes with suitable yield in three flowering groups were identified using the biplot and principal component analysis method. These genotypes can be useful for breeding programs in future studies.