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African bermudagrass (Cynodon transvaalensis Burtt‐Davy) (2n = 2x = 18) has unique morphological characteristics such as finer leaf blades and shorter internodes that are important to improving turf qualities (i.e., texture and density) as compared to other Cynodon species. It has been extensively used to cross with common bermudagrass (Cynodon dactylon Pers. var. dactylon) in developing high‐quality interspecific [C. dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] F1 hybrid cultivars for turf use. However, the molecular basis of its morphological variation is unknown. Accordingly, the objectives of this study were to estimate the heritability and identify quantitative trait loci (QTL) associated with morphological and reproductive traits. A first‐generation self‐pollinated (S1) population of 109 individuals was evaluated for plant height (PH), leaf blade width (LBW) and leaf blade length, stem internode diameter and length, and inflorescence prolificacy (IP) in a replicated field trial over three seasons (2018–2020). The broad‐sense heritability estimates ranged from 0.31 (PH) to 0.80 (IP). Twenty‐four QTL were identified and nine of them were consistent ones. Fifteen candidate genes were found at a major and consistent QTL region associated with LBW. Frequent QTL colocations were found among morphological traits and between morphological traits and IP, partially explaining the significant correlation. The findings provide critical information and resources toward understanding the genetic basis associated with morphological and reproductive traits within C. transvaalensis and could contribute to marker‐assisted selection for breeding new turf‐type bermudagrass cultivars. Core Ideas: Significant genetic variations existed for morphological and reproductive traits in African bermudagrass.Twenty‐four quantitative trait loci (QTL) were identified for morphological and reproductive traits.Fifteen candidate genes were associated with a major leaf blade width QTL. [ABSTRACT FROM AUTHOR]

Winterkill is a major concern for turf‐type bermudagrasses [Cynodon dactylon (L.) Pers. and C. dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] when cultivated in the US transition zone and frequently occurring drought conditions challenge bermudagrass management. Therefore, developing new bermudagrasses with both drought resistance and winter survivability are needed for the future sustainability of the turfgrass industry in the transition zone. How these two traits interact within bermudagrass populations is not widely reported. Accordingly, the objectives of this study were to estimate reliability for spring green‐up (SG) (as an indicator of winter survivability) and drought response in turf‐type bermudagrasses. A total of 77 experimental genotypes and 7 cultivars were planted in a randomized complete block design with 3 replications over 2 years in Goodwell, OK, USA. Substantial genetic variations were found for drought response and SG parameters when analyzed by year, but variations for SG parameters and leaf firing were not significant when analyzed across years. The reliability estimates for drought response ranged from low to moderate (i2 = 0.24–0.61), whereas the subsequent estimates for SG were low (i2 = 0.13–0.33), suggesting poor reliability. The low‐to‐moderate reliability values in SG were likely due to antecedent drought injuries, indicating that winter survivability and drought resistance may need to be evaluated in separate trials. Core Ideas: The reliability was low to moderate for drought response and low for spring green‐up when tested in the same trial.Drought stress injuries affected spring green‐up in the next year.To accurately evaluate winter hardiness, water deficit stress in the prior growing season should be prevented. [ABSTRACT FROM AUTHOR]

Turf‐type bermudagrass is susceptible to winterkill when grown in transition zone climates. Minimizing water use in turfgrass management is of societal significance. African bermudagrass (Cynodon transvaalensis Burtt‐Davy) has been extensively used to cross with common bermudagrass (C. dactylon Pers. var. dactylon) in the creation of F1 hybrid cultivars. Little information regarding the molecular basis of winter survivability and drought resistance in African bermudagrass is available. Accordingly, the objectives of this study were to quantify genetic variability and identify quantitative trait loci (QTL) associated with winter survivability traits (spring greenup, SG; spring greenup percent green cover, SGPGC; winterkill, WK), and leaf firing (LF) in African bermudagrass. A total of 109 first‐generation self‐pollinated (S1) progeny of 'OKC1163' were evaluated in a field trial in a randomized complete block design with three replications for four seasons. Significant genetic variation existed for all the traits examined, and the broad‐sense heritability estimates ranged from.36 to.54 for the winter survivability traits and.80 for LF. Ten QTL were identified for winter survivability traits and two for LF based on a preexisting high‐density linkage map, which was aligned, reoriented, and renamed as to a recently published reference genome. Seven of 12 QTL were consistently identified at least in 2 yr. The colocation of two QTL, one for winter survivability and another for LF, suggests the possibility of improving both traits together. Findings provide new insights to genetic control of winter survivability traits and LF and contribute genetic resources for marker‐assisted selection in turf‐type bermudagrass improvement. Core Ideas: Winter survivability traits and LF are critical to the development of new turf‐type bermudagrass cultivars.One hundred and nine S1 African bermudagrass progeny were characterized for winter survivability and LF. We identified 10 QTL associated with winter survivability and two QTL for LF. [ABSTRACT FROM AUTHOR]

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Bermudagrass (Cynodon dactylon Pers.) is an important warm-season perennial used extensively for turf, forage, soil conservation and remediation worldwide. However, limited genomic information has hindered the application of molecular tools towards understanding genome evolution and in breeding new cultivars. We genotype a first-generation selfed population derived from the tetraploid (4x = 36) 'A12359' using genotyping-by-sequencing. A high-density genetic map of 18 linkage groups (LGs) is constructed with 3,544 markers. Comparative genomic analyses reveal that each of nine homeologous LG pairs of C. dactylon corresponds to one of the first nine chromosomes of Oropetium thomaeum. Two nested paleo-ancestor chromosome fusions (ρ6-ρ9-ρ6, ρ2-ρ10-ρ2) may have resulted in a 12-to-10 chromosome reduction. A segmental dissemination of the paleo-chromosome ρ12 (ρ1-ρ12-ρ1, ρ6-ρ12-ρ6) leads to the 10-to-9 chromosome reduction in C. dactylon genome. The genetic map will assist in an ongoing whole genome sequence assembly and facilitate marker-assisted selection (MAS) in developing new cultivars. Tilin Fang et al. study the genome of Bermudagrass (Cynodon dactylon Pers.). They use genotyping-by-sequencing and provide a genetic map with a 10-fold increase in genetic marker density. Comparative genomics analyses reveal chromosome rearrangements. Their work will contribute to whole genome assembly efforts which will be beneficial for developing new cultivars. [ABSTRACT FROM AUTHOR]

Golf course water use continues to be highly scrutinized. Information is limited regarding minimal levels of reference evapotranspiration (ETo)-based irrigation needed to maintain adequate summer fairway performance and autumn recovery. The objectives of this 2-yr study were to (i) characterize 'Tifway' bermudagrass [Cynodon dactylon (L.) Pers.× C. transvaalensis Burtt Davy] fairway response to irrigation levels of 0.6, 0.45, 0.3, and 0.0× ETo, with and without simulated summer traffic and (ii) evaluate effects of irrigation and traffic on autumn recovery at full irrigation levels. Without traffic,≥0.3× ETo was generally adequate for maintaining acceptable quality both years. Withholding irrigation altogether resulted in unacceptable turf quality both years. Summer traffic reduced quality and percentage green cover at all irrigation levels. Canopy temperatures increased with diminishing irrigation, with up to 25°C difference between 0.6× ETo and unirrigated plots. Upon resumption of full irrigation in autumn, deficit and unirrigated treatments rebounded to 80 to 90% green cover by late autumn. However, in Year 2, only irrigated plots recovered to adequate cover levels, with unirrigated plots suffering substantial injury with only 30% green cover by late autumn. While no rooting differences were detected in Year 1, turf the 0.3× ETo and unirrigated treatments had lower root dry weights than 0.45 and 0.6× ETo treatments in Year 2. These data suggest provision of minimal deficit irrigation levels during summer drought may be important for sustaining turf viability and promoting autumn recovery of bermudagrass following successive years of summer drought stress. [ABSTRACT FROM AUTHOR]

• Celebration bermudagrass was the most shade tolerant cultivar tested. • Patriot bermudagrass was the least shade tolerant cultivar tested. • Other cultivars required 17 to 21 mol m−2 d-1 PAR to provide an acceptable lawn. Bermudagrass (Cynodon spp.) demonstrates several desirable attributes that contribute to its widespread popularity for use as a turfgrass. However, a significant limitation to more widespread usage is the poor shade tolerance of bermudagrass relative to other species (e.g., Zoysia spp.). Improvement of this trait through recurrent selection of seeded-type cultivars may contribute to increasing the adaptive range of this relatively important turfgrass. A three-year field study was conducted to evaluate the relative shade tolerance of ten commercially-available or experimental bermudagrass cultivars, including seeded-type and clonally-propagated genotypes, in Stillwater, OK. Plots were established in three blocks representing three light environments: full sun, moderate shade (40% of full sun), or severe shade (20% of full sun). Bermudagrass cultivars were evaluated for visual turf quality, normalized difference vegetation index (NDVI), visual spring green-up, and visual plant density. A turf performance index (TPI) was used to develop a relative ranking of shade tolerance among cultivars tested, and a minimum daily light integral (DLI) for each cultivar was calculated using visual turf density as the criterion. Results indicate 'Celebration' was the most shade tolerant cultivar requiring 13 mol m−2 d−1 photosynthetically active radiation (PAR) from June through September, while 'Patriot' was the least shade tolerant cultivar requiring 26 mol m−2 d-1 PAR. Other cultivars were intermediate in shade tolerance having a minimum DLI ranging from 17 to 21 mol m−2 d−1 PAR. Shade tolerance of experimental cultivars was similar to existing commercially-available cultivars suggesting further selection or breeding effort is required to improve this trait. [ABSTRACT FROM AUTHOR]

Landscape irrigation frequency restrictions are commonly imposed by water purveyors and municipalities to curtail domestic water use and to ensure adequate water supplies for growing populations during times of drought. Currently, published data are lacking concerning irrigation frequency requirements necessary for sustaining acceptable levels of turfgrass quality of commonly used warm-season turfgrass species. The objective of this 3-year field study was to determine comparative turfgrass quality of drought-resistant cultivars of four warm-season lawn species in the south-central United States under irrigation frequency regimes of 0, 1, 2, 4, and 8× monthly. Turfgrasses used in the study were based on previously reported drought resistance and included 'Riley's Super Sport' (Celebration®) bermudagrass [Cynodon dactylon (L.) Pers.], 'Palisades' zoysiagrass (Zoysia japonica Steud.), 'Floratam' st. augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and 'SeaStar' seashore paspalum (Paspalum vaginatum Swartz). During each growing season, slightly reduced irrigation volumes and bypassed events resulted from the 8× monthly treatment (34.95 cm, 38.13 cm, and 27.33 cm) compared with the 4× monthly treatment (35.36 cm, 40.84 cm, and 28.70 cm) in years 1, 2, and 3, respectively. For the once weekly treatment, the average fraction of reference evapotranspiration (ETo) supplied by effective rainfall and irrigation during the summer months was 1.22, 0.67, and 0.83 in years 1, 2, and 3, respectively, and was generally adequate to support acceptable turfgrass quality of all warm-season turfgrasses evaluated. Under the less than weekly irrigation frequency, st. augustinegrass and seashore paspalum generally fell to below acceptable quality levels because the average fraction of ETo supplied by effective rainfall and irrigation during the summer months of years 2 and 3 was 0.51, 0.39, and 0.26 for the 2× monthly, 1× monthly, and unirrigated treatments, respectively. Bermudagrass generally outperformed all other species under the most restrictive irrigation frequencies and also did not differ statistically from zoysiagrass. These results show that as irrigation frequency is restricted to less than once per week, species selection becomes an important consideration. [ABSTRACT FROM AUTHOR]

Bermudagrasses (Cynodon spp.) are the most preferred turfgrass species for athletic fields in the southern and transition zones of the United States. Developing and using bermudagrasses with superior traffic tolerance and surface playability under trafficked conditions benefits turfgrass managers, athletes, and sport organizations. A 2-year field study was conducted in Stillwater, OK, to quantify the genetic variability of traffic tolerance and surface playability from a population composed of two commercially available and 87 experimental interspecific hybrid bermudagrasses under fall simulated traffic stress. The experiment design was a randomized complete block design with three replications. Plots were subjected to 60 simulated cleat traffic events for 6 weeks in the fall of 2019 and 2020 using a Baldree traffic simulator. Bermudagrasses were evaluated for turfgrass quality (TQ), normalized difference vegetation index (NDVI), fall percent green cover (FPGC), shear strength (SS), and surface hardness (SH) after 3 and 6 weeks of traffic. Spring green-up percent green cover (SGPGC) was evaluated in the spring of 2020 and 2021. Except for SH, significant entry effects were found for all parameters and reliability estimates were moderate to high (i2 5 0.49 to 0.68) under simulated trafficked conditions. Experimental entries 17-4200-19X13, 17-4200-19X9, 17-4200-36X19, 17-5200-4X11, 18-7-2, 18-7-6, 18-8-2, 18-8-3, 18-8-7, 18-9-2, OSU1101, and OSU1664, and TifTufVR had excellent traffic tolerance. Entries 18-8-7, OSU1101, OSU1675, TifTufVR, and Tahoma 31VR demonstrated high SS. There was a large group of entries that had consistent early spring green-up across both years, including Tilin#5, 18-9-8, OKC1221, OSU1257, OSU1318, OSU1337, OSU1406, OSU1439, OSU1651, OSU1675, Tahoma 31VR, and TifTufVR. OSU1101 was the entry ranking in the top statistical grouping most often throughout the study. Findings illustrated the possibility of improving traffic tolerance and SS through breeding and using phenotypic selection could reliably select bermudagrass genotypes with improved traffic tolerance and SS in the transition zone. [ABSTRACT FROM AUTHOR]