Cool-season turfgrasses are commonly under drought stress during the summer in the United States and often require supplemental irrigation to maintain acceptable turfgrass quality. A study was conducted at Oklahoma State University to evaluate the performance and protein alteration of tall fescue during drought stress. Three diverse cultivars of mature tall fescue (‘Kentucky 31’, ‘2^nd Millennium’ and ‘Rebel Exeda’) were subjected to two treatments: well-water condition and drought. Volumetric soil water content (VSWC), leaf relative water content (RWC), turf quality (TQ) and electrolyte leakage (EL) were measured at 0, 7, and 11 d following treatments. In well-watered plants, root characteristics were measured at the end of the study period. Protein analysis was conducted to detect for changes of dehyrin protein expression. The VSWC was maintained at the same level for each treatment for all three cultivars throughout the study. There were no differences in RWC among the three cultivars under well-watered conditions throughout the study, but tall fescue RWC declined after initiation of the drought treatment. Under drought stress, TQ decreased for all three cultivars as drought stress increased but ‘Kentucky 31’ had higher TQ compared to ‘2^nd Millennium’ and ‘Rebel Exeda’ at 7d of drought treatment. After 11 of drought stress, there were no differences in TQ among the three cultivars and the average TQ rating was 2. The EL results suggested that the three cultivars had similar membrane stability under drought stress throughout the study period. Root length density, dry root weight (DRW), and root surface area (RSA) were highest in ‘2^nd Millennium’ in the 0-40 cm profile suggesting that ‘2^nd Millennium’ may have greater ability to avoid drought under field conditions. Dehydrin polypeptides of 15-, 19-, 23- and 35-kDa were detected in drought stressed tall fescue leaves and the dehydrin levels were strongly accumulated as the drought stress increased. There were no differences in soluble proteins or dehydrin protein expression among the three cultivars.

Key words: drought stress, volumetric soil water content, leaf relative water content, turf quality, electrolyte leakage, root characteristics, dehydrin protein expression.