Golf Course Management

JUN 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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72 GOLF COURSE MANAGEMENT 06.19 Drought performance and physiological responses of bermudagrass and seashore paspalum David Jespersen, Ph.D. Monique Leclerc, Ph.D. Paul Raymer, Ph.D. Drought is an important environmental stress that causes wide- spread damage to turfgrass species. Plants under drought stress will have reduced growth, wilting, loss of color, leaf firing and eventually plant death. e demand for more sustainable turfgrasses makes the development of drought-tolerant turfgrasses an essential goal for many turf scientists. e ability of a plant to survive water-limited condi- tions depends on the complex interaction of many factors, including how quickly plants uptake and transpire water, and the accumulation of protective compounds. e objectives of this study were to compare bermudagrass (Cynodon species) and seashore paspalum (Paspalum vag- inatum Swartz) cultivars exposed to drought conditions and determine their relative performance, as well as the underlying differences respon- sible for variations in drought tolerance. Methods Six cultivars — three seashore paspalums (SeaStar, Sea Isle 1 and an experimental cultivar, UGA 1743) and three bermudagrass culti- vars (Celebration, Tif Tuf and Tifway) — were established in field plots equipped with an automatic rainout shelter at the University of Geor- gia's Griffin campus. e rainout shelter has a motorized cover that moves over plots to prevent rain from affecting soil moisture levels. After establishment, plots were exposed to drought stress in the sum- mers of 2016 and 2017. During these drought periods, plots received no irrigation, and the rainout shelter prevented natural precipitation from reaching plots. Each drought period lasted for 28 days, during which weekly measurements were taken to assess drought performance and physiological differences among cultivars. Measurements included overall visual turf quality and assessment of green canopy coverage by digital image analysis and NDVI (normalized difference vegetation index) measurements. Additional measurements included leaf water content, membrane stability to estimate cellular damages, respiration rates based on CO 2 exchange, and osmotic adjustment, which measures the accumulation of solutes within cells in response to drought. Results A range of drought performance was seen among the bermudagrass and seashore paspalum cultivars when water was withheld during the trials. Tif Tuf bermudagrass was the top performer in both years of the trial because it was better able to maintain turf quality and canopy cov- erage based on NDVI (Figure 1A). In addition, Tif Tuf had greater leaf water content as drought progressed, indicating less cellular dehydra- tion (Figure 1B). Although Tif Tuf was not always significantly better than all other grasses on every measurement, it was consistently in the top statistical group across both years. In contrast, SeaStar seashore paspalum had the poorest drought performance, experiencing the greatest decline in turf quality and drought-related damage. Regardless of species, the other cultivars gen- 50 40 30 20 10 0 80 70 60 50 40 30 20 10 0 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 NDVI Leaf water content Osmotic adjustment NDVI value Relative water content (%) Change in megapascals (pressure) A B C Cultivar Celebration TifTuf Tifway SeaIsle 1 SeaStar UGA 1743 AB A A A A C C C BC BC BC BC ABC B B D D CD Figure 1. Differences in canopy characteristics estimated by (A) NDVI (normalized difference vegetation index), (B) leaf water content, and (C) osmotic adjustment among three seashore paspalum and three bermudagrass cultivars during the 2017 drought trial. Bars indicate standard error. Cultivars that share the same letter are not significantly different.

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