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Mingying Xiang, Justin Q. Moss, Dennis L. Martin and Yanqi Wu

Turfgrass managers are using reclaimed water as an irrigation resource because of the decreasing availability and increasing cost of fresh water. Much attention, thereby, has been drawn to select salinity-tolerant turfgrass cultivars. An experiment was conducted to evaluate the relative salinity tolerance of 10 common bermudagrasses (Cynodon dactylon) under a controlled environment in a randomized complete block design with six replications. ‘SeaStar’ seashore paspalum (Paspalum vaginatum) was included in this study as a salinity-tolerant standard. All entries were tested under four salinity levels (1.5, 15, 30, and 45 dS·m−1) consecutively using subirrigation systems. The relative salinity tolerance among entries was determined by various parameters, including the normalized difference vegetation index (NDVI), percentage green cover determined by digital image analysis (DIA), leaf firing (LF), turf quality (TQ), shoot vertical growth (VG), and dark green color index (DGCI). Results indicated that salinity tolerance varied among entries. Except LF, all parameters decreased as the salinity levels of the irrigation water increased. ‘Princess 77’ and ‘Yukon’ provided the highest level of performance among the common bermudagrass entries at the 30 dS·m−1 salinity level. At 45 dS·m−1, the percent green cover as measured using DIA varied from 4.97% to 16.11% among common bermudagrasses, where ‘SeaStar’ with a DIA of 22.92% was higher than all the common bermudagrass entries. The parameters LF, TQ, NDVI, DGCI, VG, and DIA were all correlated with one another. Leaf firing had the highest correlation with other parameters, which defined its value as a relative salinity tolerance measurement for common bermudagrass development and selection.

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Kevin E. Kenworthy, Dennis L. Martin and Charles M. Taliaferro

Six African bermudagrass (Cynodon transvaalensis Burtt-Davy) genotypes, one common bermudagrass [C. dactylon (L.) Pers. var. dactylon] genotype, and ‘Tifway’ (C. dactylon × transvaalensis) hybrid bermudagrass were evaluated for shoot type, leaf angle, and shoot angle. Evaluations were conducted to determine if these measurements could be used to differentiate among upright, intermediate, and prostrate growth habits. Significant differences were found for all three techniques, but attempts to group plants together as having prostrate, intermediate, or upright growth habits was not possible. ‘Tifway’ was intermediate between the African bermudagrass genotypes and the common genotype for shoot type observations, but was more similar to upright-growing African bermudagrass for leaf angle and the more prostrate-growing common bermudagrass for shoot angle. Quantification of shoot type and leaf angle did not appear as useful as shoot angle measurements for screening germplasm to identify upright or prostrate growth habits in bermudagrass.

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Jeffrey A. Anderson, Charles M. Taliaferro and Dennis L. Martin

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Mingying Xiang, Justin Q. Moss, Dennis L. Martin, Kemin Su, Bruce L. Dunn and Yanqi Wu

Bermudagrass (Cynodon sp.) is a highly productive, warm-season, perennial grass that has been grown in the United States for turfgrass, forage, pasture, rangeland, and roadside use. At the same time, many bermudagrass production and reclamation sites across the United States are affected by soil salinity issues. Therefore, identifying bermudagrass with improved salinity tolerance is important for successfully producing bermudagrass and for reclaiming salt-affected sites with saline irrigated water. In this project, the relative salinity tolerance of seven clonal-type bermudagrass was determined, including industry standards and an Oklahoma State University (OSU) experimental line. The experiment was conducted under a controlled environment with six replications of each treatment. Seven bermudagrass entries were exposed to four salinity levels (1.5, 15, 30, and 45 dS·m−1) consecutively via subirrigation systems. The relative salinity tolerance among entries was determined by normalized difference vegetation index (NDVI), digital image analysis (DIA), leaf firing (LF), turf quality (TQ), shoot dry weight (SW), visual rating (VR), and dark green color index (DGCI). Results indicated that there were variable responses to salinity stress among the entries studied. As salinity levels of the irrigation water increased, all evaluation criterion decreased, except LF. All entries had acceptable TQ when exposed to 15 dS·m−1. When exposed to 30 dS·m−1, experimental entry OKC1302 had less LF than all other entries except ‘Tifway’, while ‘Midlawn’ showed more LF than all the entries. Leaf firing ranged from 1.0 to 2.7 at 45 dS·m−1, where ‘Tifway’ outperformed all other entries. At 45 dS·m−1, the live green cover as measured using DIA ranged from 3.07% to 24.72%. The parameters LF, TQ, NDVI, DGCI, SW, and DIA were all highly correlated with one another, indicating their usefulness as relative salinity tolerance measurements.

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Kemin Su, Justin Q. Moss, Guolong Zhang, Dennis L. Martin and Yanqi Wu

Drought stress is a major limiting factor for warm-season turfgrass growth during the summer in the U.S. transition zone. Genotypic variation in drought resistance exists among bermudagrasses (Cynodon sp.), but the mechanisms of drought resistance are poorly understood. Our objectives were to investigate physiological changes in three bermudagrass cultivars under a well-watered condition and drought stress. to determine expression differences in soluble protein and dehydrin of the three cultivars under well-watered and drought stress conditions, and to identify the association between dehydrin proteins and drought tolerance. Grasses included a high drought-resistant cultivar, Celebration, a low drought-resistant cultivar, Premier, and a newly released cultivar, Latitude 36. In both well-watered and drought treatments, ‘Latitude 36’ had the highest visual quality and lower or medium electrolyte leakage among three cultivars. In the drought treatment, 16- and 23-kDa dehydrin proteins were observed in ‘Latitude 36’ but not in ‘Celebration’ or ‘Premier’. Our results indicate that the 16- and 23-kDa dehydrin expressions could be associated with drought tolerance and contribute to drought tolerance in bermudagrass.

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Tilin Fang, Yanqi Wu, Shiva Makaju, Todd Tribble, Dennis L. Martin and Justin Q. Moss

Turfgrass varietal identification is critical and allows turfgrass professionals to manage the turf based on the cultural requirements of the variety. On the Oklahoma State University (OSU) Baseball Field (OSUBF) in Stillwater, OK, some bermudagrass (Cynodon sp.) plants exhibited desirable traits but their exact identities were unknown due to the installation of multiple varieties over time. Accordingly, the major objective of this study was to identify if the desirable bermudagrass plants were from commercially available known varieties. Recently, the OSU turf bermudagrass breeding program developed and entered three fairway-type clonal bermudagrasses in the 2013 National Turfgrass Evaluation Program (NTEP) bermudagrass trial: OKC 1131, OKC 1163, and OKC 1302. The secondary objective was to create molecular marker profiles for these three experimental lines. Five OSUBF samples were analyzed using simple sequence repeat (SSR) markers, along with 24 clonal, commercially available turf bermudagrass varieties widely used in Oklahoma, the three OSU experimental clones, six randomly selected single plants from ‘Riviera’, and two controls for common bermudagrass (Cynodon dactylon) and african bermudagrass (Cynodon transvaalensis). SSR marker genotyping data indicated that the five OSUBF plants were clones of an identical bermudagrass. The OSUBF bermudagrass had the same fingerprint as ‘Astro-DLM’ bermudagrass for 14 out of 16 SSRs genotyped. Fifteen out of 30 additional SSR markers also showed differences between the OSUBF bermudagrass and ‘Astro-DLM’. The three OSU experimental clones were different from each other and had different fingerprints from the other tested varieties based on SSR profiles, indicating they are new breeding lines. These four distinct lines have potential to be released as new varieties if they demonstrate superior turf quality traits and adaptation over time.

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Gregory E. Bell, Dennis L. Martin, Kyungjoon Koh and Holly R. Han

Turfgrass performance can be assessed in terms of visual quality, but evaluators require training and may be distracted by many factors that affect accuracy and consistency. The objectives of this study were to assess a handheld optical sensor (GreenSeeker) for evaluating overall turfgrass quality in three turf species over two growing seasons, and to compare the combined time required for visual evaluation and data entry with the time required for the same functions using the handheld optical sensor. Visual quality ratings and sensor ratings were collected on schedules prescribed by the National Turfgrass Evaluation Program for the 2002 bermudagrass (Cynodon spp.), 2002 buffalograss (Buchloe dactyloides), and 2002 zoysiagrass (Zoysia spp.) studies in 2003 and 2004. Use of the sensor reduced the time required to complete data collection and data entry by 58% compared with human visual evaluation. Of the three species tested, the bermudagrass evaluation had the strongest correlation between ratings collected by the human evaluator and the sensor [r = 0.79 in 2003 (n = 343), r = 0.85 in 2004 (n = 343)]. The handheld optical sensor provided a consistent, objective evaluation of overall turfgrass quality and required less time than visual evaluation. The handheld optical sensor provides advantages for assessing turfgrass quality that cannot be realized by human evaluation, but the sensor alone is not sufficient for specific evaluations such as color, texture, or density that are routinely characterized by human evaluation.

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Brian M. Schwartz, Wayne W. Hanna, Lisa L. Baxter, Paul L. Raymer, F. Clint Waltz, Alec R. Kowalewski, Ambika Chandra, A. Dennis Genovesi, Benjamin G. Wherley, Grady L. Miller, Susana R. Milla-Lewis, William C. Reynolds, Yanqi Wu, Dennis L. Martin, Justin Q. Moss, Michael P. Kenna, J. Bryan Unruh, Kevin E. Kenworthy, Jing Zhang and Patricio R. Munoz

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Rolston St. Hilaire, Michael A. Arnold, Don C. Wilkerson, Dale A. Devitt, Brian H. Hurd, Bruce J. Lesikar, Virginia I. Lohr, Chris A. Martin, Garry V. McDonald, Robert L. Morris, Dennis R. Pittenger, David A. Shaw and David F. Zoldoske

In the United States, urban population growth, improved living standards, limited development of new water supplies, and dwindling current water supplies are causing the demand for treated municipal water to exceed the supply. Although water used to irrigate the residential urban landscape will vary according to factors such as landscape type, management practices, and region, landscape irrigation can vary from 40% to 70% of household use of water. So, the efficient use of irrigation water in urban landscapes must be the primary focus of water conservation. In addition, plants in a typical residential landscape often are given more water than is required to maintain ecosystem services such as carbon regulation, climate control, and preservation of aesthetic appearance. This implies that improvements in the efficiency of landscape irrigation will yield significant water savings. Urban areas across the United States face different water supply and demand issues and a range of factors will affect how water is used in the urban landscape. The purpose of this review is to summarize how irrigation and water application technologies; landscape design and management strategies; the relationship among people, plants, and the urban landscape; the reuse of water resources; economic and noneconomic incentives; and policy and ordinances impact the efficient use of water in the urban landscape.