Salicylic acid (SA) is one of the endogenous plant growth regulators that play an important role in the regulation of plant growth and development in response to water deficit. Genotypic-specific response to exogenous applied SA in terms of physiological, enzymatic activity, and yield traits is poorly understood in tall fescue [Lolium arundinaceum (Schreb.) Wimm. syn. Festuca arundinacea Schreb.]. Twenty genotypes of tall fescue (selected from a broad germplasm) were assessed at field condition for morphological and physiological characteristics during 2016 and 2017 under three irrigation levels (normal, mild, and intense drought stress) in the presence of two SA concentrations (0 and 1 mM). Mild and intense drought stress conditions led to depression in photosynthetic pigments including chlorophyll a and b and total chlorophyll contents, plant height, crown diameter, and forage yield, despite increases in proline content, carotenoids, catalase, peroxidase, and ascorbate peroxidase activities.Application of SA decreased the adverse effects of drought stress by elevation of photosynthetic pigments and nonenzyme and enzymatic antioxidant activities and could enhance forage yield and drought tolerance in tall fescue genotypes. High genetic variation was observed among the genotypes in their response to the application of SA under drought stress conditions, and genotypes 3L and 1E were recognized as drought tolerant and stable genotypes for future breeding programs.

In arid and semi-arid regions of the world, high temperature stress adversely affects growth and development of cool-season grasses during late spring and summer. Salicylic acid (SA) is one of the endogenous plant growth regulators that plays an important role in the regulation of plant growth and development in response to high temperature stress. The aim of the present study was to assess the effectiveness of SA in alleviating the negative effects of high temperature during the summer in different tall fescue (Festuca arundinacea Schreb.) genotypes under field conditions. Twenty genotypes of tall fescue (selected from a broad native and exotic germplasm) were assessed at field condition for morphological and physiological characteristics during 2016 and 2017 under normal irrigation in the presence of two SA concentrations (0 and 1 mM). High temperature during the summer led to induction of incomplete summer dormancy and depression in summer forage yield. Application of SA decreased the adverse effects of high temperature stress by elevation of photosynthetic pigments, proline accumulation, and increasing nonenzyme and enzymatic antioxidant activities, and could therefore be used to enhance forage yield and heat tolerance in tall fescue genotypes. The genotypes exhibited obvious differences in their response to SA application under the semiarid climate conditions of central Iran. Among the studied genotypes, 3L and 1E were recognized as heat tolerant and stable genotypes that would be preferable for regions with high temperature.

Productivity and persistence in grasses are the results of a complex combination of many variables that affect plant growth all over the growing periods. The genetic variability and inheritance of seasonal productivity, persistence, and summer dormancy and their associations are poorly understood in tall fescue. In this study, half-sib (HS) families of tall fescue derived from polycrosses, along with their corresponding parental genotypes were assessed for agro-morphological traits at three harvests, persistence, and summer dormancy in the field during 2016-2019. High genotypic variation was observed for all the measured traits in the evaluated germplasm. In both parental genotypes and HS families, summer cuts had the lowest values of forage mass than spring and autumn cuts during all years of experiment. Summer dormancy index was negatively correlated with forage production and yield-related traits. Forage mass at three cuts, persistence, and summer dormancy had lower narrow-sense heritability (h 2 PFM ) than yield-related traits, which indicates that these traits may control by small effects of many genes than yield-related traits. Based on the general combining ability (GCA) and the biplot of principal component analysis (PCA), genotypes 21M and 1E with high forage production were identified as preferable genotypes for forage use, which can be used in other breeding programs. In contrast, genotypes 17M and 4E with low forage productivity and high level of summer dormancy may be suitable for turf application. However, further experiments are needed to assess turf-related traits, root characteristics, survival and their association with summer dormancy in this germplasm. Preferable genotypes for forage use and turf application were identified for future programs.

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