Drought stress is one of the most important abiotic stress limiting the survival, persistence, growth and production of plants in many regions of the world such as Iran. Therefore in breeding program of forage grasses, information on the extent and nature of genetic variation, heritability, genetic control of the major traits associated with drought tolerance and correlations among traits is crucial for identifying and selecting favorable genotypes (with high drought tolerance, recovery and persistence) and finally, creating drought tolerant cultivar. This research was conducted in three different studies. In the first study, a total of 72 genotypes of tall fescue (24 medium, 24 late, 24 early flowering) were assessed for persistence and recovery under normal and intense drought stress conditions. Based on the field results several genotypes were chosen to evaluate their root traits at two irrigation levels (normal and intense drought stress) in pots and assess the effect of salicylic acid on drought tolerance of them in the field. The results indicated that the genotypes with greater persistence had higher recovery after the final severe drought at field. Most of the late flowering genotypes were superior in this regard. Persistence and recovery were positively correlated with root length (RL), root area (RA), root volume (RV), root weight (RW) and root to shoot ratio (R/S) under both soil moisture. Moreover, genotypes with higher recovery after drought had more RL, RA, RV and R/S than others. Salicylic acid improved the tolerance of tall fescue genotypes against drought and increased dry forage yield in both normal and drought stresses conditions, this was due to increasing yield components, photosynthetic pigments and the activity of anti-oxidant enzymes. In second study, sixteen half-sib families derived from polycross design along with their corresponding parental genotypes of tall fescue were assessed in a pot experiment for root and physiological characteristics under three irrigation levels (normal, mild and intense). These half sib families and parental genotypes along with some other grass species were evaluated in terms of summer dormancy and morphological traits in the field experiment. The results showed that drought stress decreased dry forage yield (DFY), relative water content and total chlorophyll and increased carotenoid and proline in both parental genotypes and half-sib families. Intense drought stress decreased most of the root traits at 0-30cm soil depth while at 30–60 cm depth length, area, volume and dry weight of roots were increased. A broad range of general combining ability (GCA) was observed for DFY, root and physiological characteristics at three irrigation levels. Moderate to high estimates of narrow sense heritability as well as genetic variation for root and physiological traits, indicated that phenotypic selection can be successful to attain genetic progress. Indirect selection to improve DFY was more effective through selection for root and some physiological traits. In the field experiment, high variation was observed for all measured traits in this germplasm. Variation in summer dormancy indices suggests a level of incomplete summer dormancy in this germplasm. Low narrow-sense heritability for forage yield suggested that indirect selection based on yield components and summer dormancy which have high heritability and high correlation with yield, can be more effective. Superior genotypes and families across environments were identified based on principle component analysis that would be desirable in future breeding programs. In the third study, genetic diversity of 24 tall fescue genotypes (including 16 parental genotypes and 8 other genotypes) was assessed with twenty EST-SSR markers and then the best primer combinations including four primers NFA012, NFA021, NFA033 and NFA047 was used for detection the most likely male parent in the polycross progenies. Cluster analysis of EST-SSR marker distances divided the 24 genotypes in to five groups. The EST-SSR markers allowed the identification of the most likely male parent in 177 of the offspring from a total of 926 half sib genotypes and also detection probable contaminations. These 177 genotypes were divided to 66 full-sib families which could use in future breeding programs. Key words: Drought, tall fescue, persistence, recovery, genetic analysis, root, EST-SSR marker