Scarcity of water is a severe environmental constraint to crop productivityin arid and semi-arid regions of the world. Irrigation water for product of forage and turf grasses and maintain quality turf is becoming increasingly limited in semi-arid and arid regions of Iranian pastures. Tall fescue (FestucaarundinaceaSchreb.) is considered to be more drought resistant than other cool-season turfgrasses. Although this grass is well distributed in different regions of Iran, Little research has been conducted to determine genetic differences especially for drought tolerance. This study was conducted to evaluatethe effect of drought stress and flowering time on agro morphological, phenological and physiological traits in 75 genotype of tall fescue ( Festucaarundinace ). The genotypes consisted of 25 parental lines along with their two sets of 25 progeny selection lines with conterasting maturity date (early and late). The three sets of genotypes were evaluated both under moisture stress and non-stress field environments using a randomized complete block design during two years (2008 and 2009).The results showed that drought stress significantly affected all the measured traits except for spring growth rate, days to ear emergence, days to pollination and flag leaf length. The three groups differed significantly for number of stem, flag leaf width, days to pollination, dry matter percent, regrowth dry yield, leaf to shoot ratio, prolin and carotene content. The early maturity genotypes showed better performance compared to other genotypes. There were significant differences between the 75 genotypes for all of the measured traits (with the exception of relative leaf water content of second harvest and ratio of total chlorophyll to carotene) indicating a broad genetic diversity in this germplasm. High level of heritability observed for most of the trait , implying that the majority of variation is related to genetic effects. The results showed that dry yield had negative correlation with floweing date while it was positivly correlated with plant height, crown diameter, number of stem and most of morphological traits. This may indicate that indirect selection can lead to genotypes with high yield. On the basis of stepwise regression analysis, number of stem under non-stress condition and crown diameter under stress condition justified the majority of dry yield variation and could be used for selecting high yielding genotypes. Factor analysis for all of the traits revealed eight factors under non-stress condition and seven factors under stress condition which justified more than 80 percent of the total variation.
