2017 ASHS Annual Conference

In warm, arid regions of the world, particularly those having a Mediterranean climate, both warm- and cool-season turfgrasses can be successfully grown. Historically, cool-season turfgrasses have been preferred in these climates because of their superior winter color. With increasing pressure to conserve water, there has been renewed interest in developing warm-season turfgrasses with enhanced winter color retention (chilling tolerance). The objective of the present research was to evaluate three turf-type bermudagrasses (Cynodon spp. Rich.) for their apparent winter color retention and spring regrowth potential. An experiment was conducted in a growth chamber at the Oklahoma State University Controlled Environment Research Lab in Stillwater, OK. The cultivars tested included the common bermudagrass [C. dactylon (L.) Pers.] ‘Celebration’ and the interspecific hybrid bermudagrasses (C. dactylon X C. transvaalensis) ‘Tifway’ and an experimental cultivar OKC-1131. The plants were established from sprigs and allowed to mature under optimal growing conditions (30/25 °C day/night, 680 mol m^-2 s^-1, 14-hour photoperiod). At initiation of the experiment, the ambient temperature was gradually decreased to 8/2 °C temperature regime and 10-hour photoperiod to simulate seasonal patterns. These conditions were maintained for 10 months until apparent dormancy was achieved for each plant, after which temperatures were gradually increased to 27/14 °C temperature regime and 10-hour photoperiod to simulate seasonal patterns. Plants were assessed for visual canopy green color, chlorophyll content, and electrolyte leakage at 0, 2, 4, and 6 weeks after reaching the final chilling temperature and again at 0, 3, and 6 weeks after achieving the final warming temperature. Tifway showed superior winter color retention compared to Celebration and OKC-1131. This pattern corresponds to known cold hardiness of each plant, with the most cold hardy entry being the OKC-1131 and the least cold hardy being Tifway. Interestingly, OKC-1131 was the earliest to emerge from dormancy. These results suggest that cold survivability could be related to spring green up, but may not be a good indicator of chilling tolerance. Further, it shows that genotypic variation in chilling tolerance can be successfully reproduced in controlled environment experiments.