Comparative physiological study of endophyte-infected and non-infected genotypes of Lolium perenne under drought stress.

To evaluate the effect of drought stress on some physiological characteristics of six endophyte-infected (E+) genotypes and four endophyte-free (E-) genotypes of Lolium perenne, an experiment was carried out within a completely randomized design in three replications. In pot culture, one- month stress conditions for E+ and E- genotypes of L. perenne were handled by limiting irrigation to fulfill 20% field capacity of the soil. The physiological characteristics of E+ and E- genotypes of L. perenne indicated a better resistance of E + genotypes under drought stress in terms of higher biomass and relative water content, deeper root system, and greater osmolytes accumulation and antioxidant potential. It is concluded that the osmotic adjustment (higher content of proline and total carbohydrate), lower oxidative biomarkers (H₂O₂ and MDA content), higher enzymatic and nonenzymatic components (phenolic, GSH), and induction of stress hormone (Abscisic acid (ABA)) are key protective mechanisms in E + genotypes under drought stress. In contrast, E- genotypes of Lolium had some compliant mechanisms to cope with drought stress, including enhanced antioxidant activity, presented lower lipid peroxidation, improved osmolyte accumulation, induction of ABA hormone and up-regulation of Lptip1;1 and Lptip1;2; aquaporin genes. It seems that E- genotypes apply the defensive antioxidant mechanism more than E + genotypes and use more ABA as a critical component of the stress acclimation mechanism in drought conditions.