Performance of multiple turfgrass species during prolonged heat stress and recovery in a controlled environment

Increasing temperatures associated with climate change will be the next challenge for crop improvement, especially for turfgrass species that are often grown in urban green spaces. Previous research on turfgrass heat stress tolerance has been limited to a small number of species and cultivars with different heat stress conditions between studies; therefore, we assessed heat stress tolerance of 34 turfgrasses representing 14 species. Four replicates of each entry were established for at least 12 wk and then subjected to 49 d of heat stress (35/25 °C day/night) followed by a 4 wk recovery period (25/15 °C day/night). Turfgrass entries were assessed using the normalized difference vegetative index, the percentage of green obtained with digital image analysis, and membrane stability estimated by electrolyte leakage. Buffalograss [Bouteloua dactyloides (Nutt.) J.T. Columbus], Kentucky bluegrass (Poa pratensis L.), tall fescue [Schedonorus arundinaceus (Schreb.) Dumort], and slender creeping red fescue (Festuca rubra ssp. littoralis) were more tolerant of heat stress than the other species. The Canada bluegrass (Poa compressa L.), blue grama [Bouteloua gracilis (Willd. ex Kunth.) Lag. ex Griffiths], and smooth brome (Bromus inermis Leyss.) cultivars were all tolerant of heat stress; however, only one cultivar for these three species was tested, making species-wide generalizations difficult. In some cases, the cultivars and/or selections within a given species differed in heat stress response. Almost all entries were able to recover from the heat stress by the end of the recovery period. Altogether, we were able to identify turfgrasses that should perform adequately in high-temperature urban environments.