Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases catalyze the production of superoxide, a type of reactive oxygen species (ROS). In plants, the NADPH oxidase homologs have been identified as respiratory burst oxidase homologs (Rboh). They are involved in ROS production in response to drought stress. Three entries of tall fescue (Festuca arundinacea Schreb.) were used for analyses in the present study: tolerant (‘Isfahan’) and sensitive (‘Quchan’) accessions to drought during the germination stage, selected from 14 wild populations in Iran, as well as ‘Barvado’ as a control. Partial sequence of the Festuca respiratory burst oxidase‐D (FrbohD) gene was isolated from Barvado. We compared expression levels of the FrbohD gene as well as hydrogen peroxide (H2O2), catalase activity and some biochemical responses among the three entries. Gene expression was evaluated for leaf and shoot samples subjected to 3, 6, and 9 d without water. The transcript level of FrbohD, H2O2 content, and catalase activity increased in Quchan under drought stress. It appears that lower levels of FrbohD gene transcription and H2O2 concentration in F. arundinacea leaves contributed to drought stress tolerance in Isfahan. Total protein and total soluble carbohydrate content also increased significantly in Isfahan when it was subjected to drought stress. Isfahan exhibited drought resistance through various strategies, which could serve as selection criteria for improving drought resistance in turfgrass breeding programs.

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Tall fescue (Festuca arundinacea Schreb.) is an important forage and turf grass species adapted to cold, arid and semiarid environments. Germination and seedling establishment of F. arundinacea cultivars is constrained by the low soil moisture found in these regions. Genome size was found to positively correlate with latitude of origin, suggesting that structural changes in DNA may play a role in environmental adaptation. We investigated the effects of low soil moisture on the germination and early establishment and their correlation with relative DNA content using 14 wild F. arundinacea populations collected from various regions in Iran and two commercial turf cultivars. The populations were evaluated under 100% (−0.03 matric potential [MPa]), 80% (−0.2), 60% (−0.6) and 40% (−1.4) field capacity (FC) conditions. Seed germination and root and leaf growth decreased under reduced soil water content. Cluster analysis revealed that the populations fell into four groups. Populations in cluster I showed the greatest tolerance to low soil moisture and cluster IV was the least tolerant. ‘Isfahan’ and ‘Gonabad’ populations had the best final germination and longer leaf and root length at 40% FC. Studies to identify indices that were involved in drought resistance revealed that final germination, leaf length and seedling vigor index were most important evaluating indicators for F. arundinacea populations. Flow cytometric relative DNA content of the wild populations was negatively correlated with germination, leaf length and seedling vigor index. The drought tolerance populations in cluster I could be potentially useful germplasm for a breeding program to develop superior cultivars for arid and semiarid regions.