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The susceptibility of warm-season turfgrasses such as bermudagrass (Cynodon spp.) to winter injury in the transition zone is a major concern. Therefore, the objective of the study was to evaluate five golf course putting green-type experimental genotypes (OKC6318, OKC0805, OKC1609, OKC0920, and OKC3920) and three commercially available bermudagrasses (‘Champion Dwarf’, ‘TifEagle’, and ‘Tahoma 31’) for freeze tolerance by subjecting them to 11 freezing temperatures (–4 to –14 °C) under controlled environment conditions. The experiment was conducted in batches, with four genotypes per batch, and each batch was replicated in time. The mean lethal temperature to kill 50% of the population (LT₅₀) for each genotype was determined. There were significant differences in LT₅₀ values among the bermudagrass genotypes. ‘Champion Dwarf’ had an LT₅₀ value ranging from –5.2 to –5.9 °C across all three batches. The experimental genotypes tested in this study had LT₅₀ values ranging from –7.0 to –8.1 °C and were each lower than that of ‘Champion Dwarf’. ‘Tahoma 31’, the top performing genotype, had an LT₅₀ value ranging from –7.8 to –9.0 °C across all three batches. OKC 3920 was the only experimental genotype with an LT₅₀ value in the same statistical group as ‘Tahoma 31’. The information gained from this research would be useful for breeders to gauge the genetic gain in freeze tolerance in breeding golf course putting green-type bermudagrass.

The availability of freshwater is a growing concern throughout the world as it is an increasingly valuable and limited resource. Alternative water resources such as recycled water low in quality and high in salinity are now frequently used to irrigate turfgrass. However, irrigating with highly saline water can affect the growth, performance, appearance, and quality of turfgrass. Bermudagrass (Cynodon sp.) is the most commonly used turfgrass throughout the southern United States. In this study, the spectral reflectance and visual response of ‘Riviera’ common bermudagrass (Cynodon dactylon) were evaluated by consecutively irrigating with 12 salinity concentrations (4–48 dS·m⁻¹) in increments of 4 dS·m⁻¹ via manual overhead irrigation for 30 days. The experiment was replicated in time in a controlled environment with four replications for each salinity treatment and control. ‘Riviera’ maintained a leaf firing (LF) value above 5 (rated on a scale from 1 to 9) when irrigated with 28 dS·m⁻¹ for 30 days. Also, the LF value did not fall below 2 when irrigated with a salinity concentration of 48 dS·m⁻¹ for 30 days, suggesting high salinity tolerance of ‘Riviera’. However, in this study, the normalized difference vegetation index (NDVI) had a lower ability to detect the increase in salinity stress due to the limited area measured by the NDVI measuring device used. An increase in sodium ion concentration was observed in the shoot with increasing salinity concentrations. The NDVI was highly correlated (r = 0.93) to LF, indicating the usefulness of NDVI as a tool to measure the magnitude of salinity stress. The multiple linear regression analysis revealed that the data showed a linear response to salinity stress with LF (r ² = 0.86) and NDVI (r ² = 0.76) decreasing linearly as the salinity concentration and days of treatment increased. This study provides an accurate depiction of the spectral and visual responses of ‘Riviera’ when exposed to multiple salinity concentrations with narrow increments.

Cell and plastid membranes play a critical role in plant response to chilling stress. Fall color retention (chilling tolerance) of bermudagrass (Cynodon sp.) is known to vary with cultivar and management practices. A growth chamber study was conducted to characterize the lipid composition of three bermudagrasses in response to chilling stress. The grasses selected were ‘Tahoma 31’ (chilling-sensitive) and ‘Tifway’ (chilling-tolerant) interspecific hybrid bermudagrass (C. dactylon × C. transvaalensis) and ‘Celebration’ common bermudagrass (C. dactylon), which served as an internal standard. Plants were subjected to simulated fall conditions defined as an 8/2 °C (day/night) temperature regime with 10-hour photoperiod and evaluated for chilling response for 42 days before allowing plants to enter an apparent dormancy. Plant leaves were sampled for lipidomics analysis at 0, 14, and 42 days of chilling treatment (DOT) and again after 40 days of recovery from dormancy (during which temperatures were adjusted to mimic average spring conditions for Oklahoma). ‘Tifway’ demonstrated the lowest electrolyte leakage (EL) and visual discoloration at 42 DOT, while ‘Tahoma 31’ had the greatest EL and discoloration on the same date, and ‘Celebration’ was intermediate of the two. Prolonged exposure to chilling stress generally increased digalactosyldiacylglycerol and phosphatidylcholine (PC) content and decreased monogalactosyldiacylglycerol (MGDG) content, with ‘Tahoma 31’ showing the greatest increase in PC and decrease in MGDG. The double bond index, an indicator of fatty acid unsaturation, was greatest in ‘Tifway’ at 42 DOT. Each cultivar increased in fatty acid unsaturation, with Tifway demonstrating the greatest increase in MGDG unsaturation. Multivariate discriminant analysis identified six individual lipid species that contributed most to the cultivar response to chilling. These findings suggest unsaturation level of plastid lipids, particularly MGDG, is important for chilling tolerance and therefore fall color retention of bermudagrass. Furthermore, this study provides evidence that chilling tolerance can be negatively associated with freezing tolerance in bermudagrass.

Suitable tensile strength is essential for sod harvest, transport, and installation. Thirty-nine bermudagrass (Cynodon sp.) entries were evaluated for sod handling quality (SHQ) and sod tensile strength (STS) during 2014–15. The SHQ (a discontinuous qualitative parameter) was evaluated using a 1 to 5 scale with 1 = complete pad separation during handling and 5 = no cracking or separation in the sod pad with excellent quality. The STS (a quantitative parameter) was determined using the force required to shear/separate the sod pad. Sod harvests were conducted at 14, 22, and 24 months after planting (MAP). The entry, harvest date, and their interaction affected STS and SHQ. Entries OKC 1302 and 12-TSB-1 had greater STS than ‘Patriot’ but less STS than ‘Latitude 36’, ‘Tifway’, ‘Astro’, and ‘TifGrand’. The seeded entry PST-R6T9S had the lowest STS and SHQ. The overall mean STS and SHQ were lowest at 22 MAP, which could be attributed to the slow recovery of the entries after Winter 2014. A strong positive correlation (r = 0.92) between STS and SHQ suggests that SHQ can be used as a rapid field method to estimate suitability for sod harvest. A predictive linear relationship between overall STS and overall SHQ (r ² = 0.85) found predicted STS values of 8.5, 22.6, 36.8, and 51.0 kg⋅dm^–2 for overall mean SHQ ratings of 2, 3, 4, and 5, respectively. The results of this work will help sod producers in cultivar selection and will aid breeders in making commercialization decisions.