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Smutgrass is an invasive weed species that can quickly outcompete bahiagrass because of its aggressive growth, prolific seed production, and rhizomatous nature. Total renovation of bahiagrass pastures or hayfields is generally not a feasible or economically viable option for most producers. Therefore, controlling the continual spread of smutgrass will require an integrated weed management (IWM) plan that incorporates multiple strategies. The objective of this study was to test the interactions of herbicides and fertilizers on smutgrass control in bahiagrass and determine the most efficacious and economical IWM plan for low-input bahiagrass systems. This research was conducted on a mixture of ‘Tifton 9’ and ‘Pensacola’ bahiagrass at the Alapaha Beef Station in Alapaha, GA. The study design was a randomized complete block with a three-by-four factorial treatment arrangement with six replications. Fertility treatments included 56 kg N ha–1 (ammonium nitrate, 34% N) + 56 kg K2O ha–1, 56 kg N ha–1, and an unfertilized control. Smutgrass was reduced to 2O resulted in an improved bahiagrass stand as timely weed suppression removed competition, while fertilizer provided essential nutrients for optimum growth to fill in the gaps. Combining herbicide and fertilizer is a more economical option for producers when compared to a complete bahiagrass renovation.

A 3-year experiment was conducted to evaluate the performance and playability of 24 coarse-textured zoysiagrass (Zoysia spp. Willd.) experimental genotypes in comparison to five commercially available cultivars maintained as a low-maintenance turf across multiple climates (Indiana, North Carolina, Georgia, Arizona, and California). Following establishment in 2018, plots were maintained under low-maintenance regimes and evaluated for quality, density, uniformity, color, winterkill damage, drought resistance, and golf ball lie in 2019 and 2020. A turf performance index (TPI) was calculated for each treatment at each site, which represented the number of times the treatment occurred in the top statistical group. The unique climate for each site led to differences in TPI scores. For instance, the arid climates of Arizona and California resulted in distinct differences in performance among treatments compared to the other sites. However, consistencies in performance across sites were also observed. For example, the 2018−2019 winter resulted in winterkill differences among entries in both Indiana and North Carolina, which led to some similarities in TPI. Furthermore, the southern humid climates of North Carolina and Georgia produced consistencies in overall TPI. Under the minimal inputs and the hot-humid or arid climates evaluated in this study, all of the check cultivars were some of the poorest performing treatments, which clearly illustrates there is a need for breeding programs to develop zoysiagrass genotypes for these climates. However, experimental lines that exhibited excellent persistence under these conditions were identified indicating the genetic potential for wider adaptation to lower input environments exists within the species.

Shade caused by trees or buildings can affect the quality and growth of turfgrasses. Thus, breeding for shade tolerance is an essential component of most turfgrass improvement programs. The objective of this study was to evaluate the performance of seashore paspalum (Paspalum vaginatum Sw.) breeding lines under shade in multi-environment trials. Germplasm sources were 20 lines from the University of Georgia seashore paspalum breeding program and two checks, the cultivars 'SeaDwarf' and 'SeaStar'. Field trials were conducted from 2016 to 2019 under shade structures designed to reduce ambient sunlight at three locations: Citra (FL), Tifton (GA), and Raleigh (NC). The response variables evaluated were percent living ground cover (%GC), dark green color index (DGCI), canopy height (CH) and turfgrass quality (TQ). Data were analyzed by mixed model approaches using ASReml-R, and the t-statistics were used to group the entries. Significant genetic variances were observed in the single-location-repeated-measures analysis for CH and DGCI at Citra and Tifton, %GC at Citra, and TQ at Raleigh. Spearman correlations of the predicted values for entries between locations ranged from low to moderate, with the exception of between Citra and Tifton (0.76) for CH. There were a few breeding lines with superior performance to the entry average for all traits for which the entry variance was significant. In conclusion, genetic variability was observed for all traits and superior seashore paspalum breeding lines for multiple traits were identified under shade.

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an important pest of warm-season turfgrass species, including bermudagrass (Cynodon spp.). Bermudagrass is a popular turfgrass that is widely planted on golf courses, athletic grounds, and ornamental landscapes across the country and throughout the world. Spodoptera frugiperda infestation is often sporadic; however, when it does occur, damage can be severe. Host plant resistance against S. frugiperda can be a valuable tool for reducing or preventing the use of insecticides. Therefore, the objective of this study was to determine resistance against S. frugiperda in a few promising bermudagrasses. Fourteen experimental bermudagrass genotypes plus two control cultivars, ‘Zeon’ zoysiagrass (resistant control) and ‘TifTuf’ bermudagrass (susceptible control), were evaluated against S. frugiperda to determine host plant resistance in the laboratory. The results showed that the resistant control, ‘Zeon’ zoysiagrass, was more resistant than the other genotypes to S. frugiperda larvae. To determine the response of the experimental lines to S. frugiperda as compared with that of the controls, three indices were developed based on survival, development, and overall susceptibility. According to the susceptibility index, ‘13-T-1032’, ‘T-822’, ‘11-T-510’, ‘12-T-192’, ‘11-T-56’, ‘09-T-31’, ‘11-T-483’, and ‘13-T-1067’ were the top-ranked bermudagrasses. Among these, the responses of ‘13-T-1032’, ‘T-822’, ‘11-T-510’, ‘11-T-56’, ‘09-T-31’, and ‘11-T-483’ were comparable to that of ‘TifTuf’, and antibiosis was the underlying mechanism of resistance. Additionally, larval length, head capsule width, and weight were negatively associated with the days of pupation and adult emergence and positively associated with pupal length, thorax width, and weight. These results will help refine future breeding and with investigations of resistance against the fall armyworm.

Heavily shaded environments often limit the performance and persistence of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis), therefore a field-based shade study was performed to determine whether different mowing heights (0.5 and 1.5 inch) or two trinexapac-ethyl (TE) growth regulator management treatments (control and 2 oz/acre) allow either ‘TifSport’ or ‘TifGrand’ hybrid bermudagrass to persist under 77% shade. Turfgrass quality (TQ), green cover, normalized difference vegetation index (NDVI), and dark-green color index (DGCI) were evaluated on the two cultivars under a shade structure in Tifton, GA, during 2010 and 2011. Neither of the cultivars maintained acceptable TQ throughout the entire year under 77% shade, although ‘TifGrand’ displayed adequate TQ at the higher mowing height (1.5 inch) and demonstrated more shade tolerance than ‘TifSport’, as indicated by TQ, green cover, and NDVI. The TE application did not enhance the turf performance of ‘TifSport’ under 77% shade when mowed at 0.5 inch, but it improved turf performance of ‘TifGrand’ at the same height. The effect of TE application was cultivar and mowing height dependent under this heavily shaded environment, which warrants future study to determine the best management practices of these cultivars as well as continued efforts to develop new, shade-tolerant bermudagrass hybrids.

Weeds are a persistent problem on sod farms, and herbicides to control different weed species are one of the largest chemical inputs. Recent advances in unmanned aerial systems (UAS) and artificial intelligence provide opportunities for weed mapping on sod farms. This study investigates the weed type composition and area through both ground and UAS-based weed surveys and trains a convolutional neural network (CNN) for identifying and mapping weeds in sod fields using UAS-based imagery and a high-level application programming interface (API) implementation (Fastai) of the PyTorch deep learning library. The performance of the CNN was overall similar to, and in some classes (broadleaf and spurge) better than, human eyes indicated by the metric recall. In general, the CNN detected broadleaf, grass weeds, spurge, sedge, and no weeds at a precision between 0.68 and 0.87, 0.57 and 0.82, 0.68 and 0.83, 0.66 and 0.90, and 0.80 and 0.88, respectively, when using UAS images at 0.57 cm–1.28 cm pixel–1 resolution. Recall ranges for the five classes were 0.78–0.93, 0.65–0.87, 0.82–0.93, 0.52–0.79, and 0.94–0.99. Additionally, this study demonstrates that a CNN can achieve precision and recall above 0.9 at detecting different types of weeds during turf establishment when the weeds are mature. The CNN is limited by the image resolution, and more than one model may be needed in practice to improve the overall performance of weed mapping.

Bermudagrass (Cynodon (L.)) is the most important warm-season grass grown for forage or turf. It shows extensive variation in morphological characteristics and growth attributes, but the genetic basis of this variation is little understood. Detection and tagging of quantitative trait loci (QTL) affecting above-ground morphology with diagnostic DNA markers would provide a foundation for genetic and molecular breeding applications in bermudagrass. Here, we report early findings regarding genetic architecture of foliage (canopy height, HT), stolon (stolon internode length, ILEN and length of the longest stolon LLS), and leaf traits (leaf blade length, LLEN and leaf blade width, LW) in 110 F1 individuals derived from a cross between Cynodon dactylon (T89) and C. transvaalensis (T574). Separate and joint environment analyses were performed on trait data collected across two to five environments (locations, and/or years, or time), finding significant differences (P < 0.001) among the hybrid progeny for all traits. Analysis of marker-trait associations detected 74 QTL and 135 epistatic interactions. Composite interval mapping (CIM) and mixed-model CIM (MCIM) identified 32 main effect QTL (M-QTL) and 13 interacting QTL (int-QTL). Colocalization of QTL for plant morphology partially explained significant correlations among traits. M-QTL qILEN-3-2 (for ILEN; R2 = 11–19%), qLLS-7-1 (for LLS; R2 = 13–27%), qLEN-1-1 (for LLEN; R2 = 10–11%), and qLW-3-2 (for LW; R2 = 10–12%) were ‘stable’ across multiple environments, representing candidates for fine mapping and applied breeding applications. QTL correspondence between bermudagrass and divergent grass lineages suggests opportunities to accelerate progress by predictive breeding of bermudagrass.

Drought avoidance is dictated by a collection of traits used to maintain tissue hydration levels and turgidity during water-limited conditions. These traits include deeper and more extensive rooting and the closure of stomata to limit the transpiration of water from leaves. Zoysiagrasses are a group of warm-season turfgrasses, including Zoysia japonica and Zoysia matrella, that are valued for their turfgrass quality; however, they are susceptible to drought relative to other warm-season turfgrass species. The objectives of the study were to determine 1) differences in drought avoidance among a collection of zoysiagrasses and 2) which drought avoidance traits contributed to these differences. Fifteen zoysiagrass genotypes were exposed to either drought or control conditions in a greenhouse environment. Overall performance was assessed by evaluating turfgrass quality and percentage green cover. Drought avoidance was estimated by measuring leaf hydration levels and drought avoidance traits [including stomatal conductance (gS)]; root traits such as total root biomass, specific root length (SRL), and root length density (RLD) were measured. Compared with commercial cultivars Meyer, Palisades, or Zeon, some experimental genotypes maintained greater turfgrass quality during drought, with experimental genotype ‘09-TZ-54-9’ having a quality rating of 7.8 after 20 days of drought compared with 5.3 in ‘Zeon’, 5.2 in ‘Meyer’, and 5.0 in ‘Palisades’. A range of belowground traits such as root biomass was also found to be associated with drought avoidance, with experimental ‘09-TZ-53-20’ having 1.03 total grams, and 2.39 total grams in ‘10-TZ-1254’, compared with 1.14, 1.66, and 3.44 total grams in ‘Meyer’, ‘Zeon’, and ‘Palisades’, respectively. Significant differences in drought avoidance were found among the 15 genotypes, with both belowground rooting traits and aboveground factors affecting transpiration influencing plant performance.

In the U.S. since 2013, the sugarcane aphid is a perennial pest to all types of sorghum. Rating sugarcane aphid population density, plant damage, and other traits in sorghum requires a large amount of labor and ratings, especially damage ratings, may vary by evaluator. Thus Unmanned Aerial Systems (UAS)–based imagery may be exceedingly useful to more accurately quantify the effects on sorghum caused by sugarcane aphids. This study quantified the dynamic nature of sugarcane aphid infestations on silage sorghum varieties using UAS-based imagery data, and demonstrated the UAS-based measurements correlated to ground measurements. Two UAS platforms equipped with RGB (red, green, and blue) and multispectral cameras respectively were used to evaluate the silage sorghum variety trials during the growing seasons of 2019 and 2020. For the purpose of high throughput phenotyping in sorghum breeding, a new workflow scheme was developed including UAS image processing, raster calculation, DTM (digital terrain model) and CHM (canopy height model) generation, image extraction of sorghum plants, and tabular dataset generation from zonal statistics for further statistical analyses. Ground-based measurements included aphid sampling, aphid damage ratings, plant height, and biomass yields. The normalized difference red edge index (NDRE) and canopy cover collected by the UAS showed negative linear relationship with aphid damage ratings in both trials (R2 = 0.55–0.64). In addition to assessing spatial differences among the varieties in 2019, temporal change in both NDRE and canopy cover from the baseline sampling date in 2020 better estimated aphid damage, R2 of 0.68 and 0.79 respectively, than using the spatial difference of NDRE (R2 = 0.55) and canopy cover (R2 = 0.57) before harvest. Plant height (R2 = 0.84, Root-Mean-Square Error (RMSE) = 0.16 m) can be estimated with efficiency and precision using UAS-derived measurements during high throughput phenotyping of sorghum. Fresh yield estimates for the primary harvests were consistent in both years, but green yield estimates differed among harvests and need to be improved. Future development of UAS-based high throughput phenotyping would benefit from increased temporal resolutions of growth parameters and vegetation indices throughout a growing season.

Bermudagrass lags in genomic and molecular breeding resources, particularly regarding a critical mass of robust, reproducible, and highly polymorphic molecular markers like simple sequence repeats (SSR). Here, 2017 sugarcane EST-SSR primer pairs (PPs) were screened for transferability and polymorphisms against commercial triploid hybrids and representatives of their parental species, tetraploid Cynodon dactylon and diploid C. transvaalensis. Fifty-four percent of PPs amplified target SSR in at least one of the two species, while 62% of these ‘transferable’ SSR were polymorphic. A subset of 228 polymorphic markers was utilized for genotyping 24 samples that included: 10 ‘Tif’ series cultivars (i.e., released from Tifton, GA), their parental species, 10 F1 hybrids between the two species, and two diverse Sorghum spp. A total of 90 and 144 PPs produced reproducible bands in the bermudagrass samples and the sorghum species, respectively. While 63 (70%) PPs were polymorphic among members of the ‘Tif’ diversity panel, 79 (54.8%) were polymorphic between the sorghum species. Further, 57 PPs polymorphic in the ‘Tif’ diversity panel were genotyped against 3 experimental lines and 7 commercial hybrids including ‘TifTuf’, a recent addition to the ‘Tif’ series. Joint analysis of 24 genotypes grouped bermudagrass accessions into two main clusters, one including C. dactylon and the other including C. transvaalensis. A small set of informative SSR readily differentiated the cultivar groups and identified potentially mischaracterized cultivars, but did not differentiate among mutants within cultivar groups. Heterologous EST-SSR from sugarcane are useful sources of polymorphic markers for cultivar identification in bermudagrass, and build on existing marker resources to facilitate genetic mapping, QTL analysis, and marker assisted selection.

Quantitative spectral reflectance data have the potential to improve the evaluation of turfgrasses in variety trials when management practices are factors in the testing of turf aesthetics and functionality. However, the practical application of this methodology has not been well developed. The objectives of this research were 1) to establish a relationship between spectral reflectance and turfgrass quality (TQ) and percent green cover (PGC) using selected reference plots; 2) to compare aesthetic performance (TQ, PGC, and vegetation indices) and functional performance (surface firmness); and 3) to evaluate lignin content as an alternate means to predict surface firmness in turfgrass variety trials of hybrid bermudagrass [Cynodon dactylon × C. transvaalensis]. A field study was conducted on mature stands of three varieties (‘TifTuf’, ‘TifSport’, and ‘Tifway’) and two experimental lines (04-47 and 04-76) at two mowing heights (0.5 and 1.5 inch) and trinexapac-ethyl application (0.15 kg·ha−1 and nontreated control) treatments. Aesthetic performance was estimated by vegetation indices, spectral reflectance, visual TQ, and PGC. The functional performance of each variety/line was measured through surface firmness and fiber analysis. Regression analyses were similar when using only reference plots or all the plots to determine the relationship between individual aesthetic characteristics. Experimental line 04-47 had lower density in Apr. 2010, whereas varieties ‘TifTuf’, ‘TifSport’, and ‘Tifway’ were in the top statistical group for aesthetic performance when differences were found. ‘TifSport’ and ‘Tifway’ produced the firmest surfaces, followed by ‘TifTuf’, and finally 04-76 and 04-47, which provided the least firm surface. Results of leaf fiber analysis were not correlated with turf surface firmness. This study indicates that incorporating quantitative measures of spectral reflectance could reduce time and improve precision of data collection as long as reference plots with adequate range of green cover are present in the trials.

Recent advances in remote sensing technology, especially in the area of Unmanned Aerial Vehicles (UAV) and Unmanned Aerial Systems (UASs) provide opportunities for turfgrass breeders to collect more comprehensive data during early stages of selection as well as in advanced trials. The goal of this study was to assess the use of UAV-based aerial imagery on replicated turfgrass field trials. Both visual (RGB) images and multispectral images were acquired with a small UAV platform on field trials of bermudagrass (Cynodon spp.) and zoysiagrass (Zoysia spp.) with plot sizes of 1.8 by 1.8 m and 0.9 by 0.9 m, respectively. Color indices and vegetation indices were calculated from the data extracted from UAV-based RGB images and multispectral images, respectively. Ground truth measurements including visual turfgrass quality, percent green cover, and normalized difference vegetation index (NDVI) were taken immediately following each UAV flight. Results from the study showed that ground-based NDVI can be predicted using UAV-based NDVI (R2 = 0.90, RMSE = 0.03). Ground percent green cover can be predicted using both UAV-based NDVI (R2 = 0.86, RMSE = 8.29) and visible atmospherically resistant index (VARI, R2 = 0.87, RMSE = 7.77), warranting the use of the more affordable RGB camera to estimate ground percent green cover. Out of the top ten entries identified using ground measurements, 92% (12 out of 13 in bermudagrass) and 80% (9 out of 11 in zoysiagrass) overlapped with those using UAV-based imagery. These results suggest that UAV-based high-resolution imagery is a reliable and powerful tool for assessing turfgrass performance during variety trials.

Main conclusion Some interspecific hybrid bermudagrass cultivars used on golf course putting greens are genetically unstable, which has caused phenotypically different off-type grasses to occur in production nurseries and putting surfaces. Management practices to reduce the occurrence of off-type grasses in putting green surfaces and the effect they can have on putting quality and performance need to be researched until genetically stable cultivars are developed. Golf course putting green surfaces in subtropical and tropical climates are typically planted with an interspecific hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy), because of the superior putting quality and performance of these cultivars. ‘Tifgreen’ was one of the first interspecific hybrids developed for putting green use in lieu of common bermudagrass. However, off-type grasses began appearing in established Tifgreen stands soon after commercial release. Off-type grasses are those with different morphology and performance when compared to the surrounding, desirable cultivar. Off-types have the potential to decrease surface uniformity, which negatively affects putting surface quality. However, several unique off-types from Tifgreen have been selected as commercial cultivars, the first being ‘Tifdwarf’; then ‘Floradwarf’, ‘MS-Supreme’, ‘Pee Dee-102’, and ‘TL-2’, identified later. The cultivars ‘Champion Dwarf’, ‘P-18’, ‘RJT’, and ‘Emerald Dwarf’ were subsequently selected as off-types in Tifdwarf. The naturally occurring off-types and cultivars that have been identified within the Tifgreen family have widely differing phenotypes; however, they are reported to be genetically similar, supporting the hypothesis that their occurrence is a result of somatic mutations. Genetic instability in currently available commercial cultivars is likely to lead to the continued presence of off-types in production nurseries and putting greens. Additional research is needed to understand the nature of genetic instability in Tifgreen-derived cultivars and how to manage its consequences to develop new cultivars, but also strategies for eradication of off-types in pedigree nursery production and end-site putting greens.

Overexpression of a native gene can cause expression of both introduced and native genes to be silenced by posttranscriptional gene silencing (PTGS) mechanisms. PTGS mechanisms rely on sequence identity between the transgene and native genes; therefore, designing genes with mutations that do not cause amino acid changes, known as synonymous mutations, may avoid PTGS. For proof of concept, the sequence of acetyl-coA carboxylase (ACCase) from creeping bentgrass (Agrostis stolonifera L.) was altered with synonymous mutations. A native bentgrass ACCase was cloned and used as a template for the modified gene. Wild-type (WT) and modified genes were further modified with a non-synonymous mutation, coding for an isoleucine to leucine substitution at position 1781, known to confer resistance to ACCase-inhibiting herbicides. Five-hundred calli of creeping bentgrass 'Penn A-4' were inoculated with Agrobacterium containing either the WT or modified genes, with or without the herbicide-resistance mutation. Six herbicide-resistant-transgenic events containing the modified gene with the 1781 mutation were obtained. Transcription of the modified ACCase was confirmed in transgenic plants, showing that gene-silencing mechanisms were avoided. Transgenic plants were confirmed to be resistant to the ACCase-inhibiting herbicide, sethoxydim, providing evidence that the modified gene was functional. The result is a novel herbicide-resistance trait and shows that overexpression of a native enzyme with a gene designed with synonymous mutations is possible.

The objective of this study was to characterize and compare mechanisms of drought avoidance and tolerance, specifically rooting characteristics, osmotic adjustment and antioxidant metabolism among different bermudagrasses. Six different bermudagrasses (‘Celebration’, ‘Tifway’, ‘TifTuf’, ‘UGB-70′, ‘UGB-42′ and ‘UGB-208’) were grown in field and growth chamber conditions and exposed to drought treatments. A range of drought performance was observed across bermudagrass genotypes with TifTuf being only the genotype to maintain a minimum acceptable turf quality rating of 6 at the end of drought treatments under field conditions. Along with TifTuf, UGB-42 and UGB-70 performed well in terms of percent green cover, normalized difference vegetation index (NDVI), leaf water status and membrane stability in both field and growth chamber conditions indicating these three genotypes had the best drought performance in the current study. Drought tolerant bermudagrasses were able to better maintain photosynthesis and transpiration after being exposed to drought. TifTuf had 15, 27 and 200 % greater osmotic adjustment (OA) compared to poor performing Celebration in 2017 and 2018 field, and grown chamber experiments, respectively. Antioxidant enzyme activities, including activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT) and glutathione reductase (GR), were mostly greater in drought-tolerant bermudagrasses. Greater antioxidant activities reduced formation of damaging H2O2 and lipid peroxidation in TifTuf, UGB-42 and UGB-70. TifTuf had 25 % greater total dry weight partitioned to roots compared to poorer performing UGB-208. Root viability was the greatest in UGB-42 and root length density (RLD) were greater in UGB-42 and UGB-70 compared to many other bermudagrasses. Results indicated better drought performances of bermudagrasses could be attributed both drought tolerance (particularly OA and antioxidant mechanisms) and desiccation avoidance (total dry weight partitioned to roots and root viability) traits.

Hybrid bermudagrasses (Cynodon dactylon × C. transvaalensis) typically have excellent wear tolerance when compared with other turfgrass species. This trait should be evaluated during variety development to reduce the risk of failure when new grasses are planted in areas with traffic stress. The objective of this research was to evaluate the wear tolerance of four hybrid bermudagrasses with differing morphological characteristics. Traffic was applied to the hybrid bermudagrass varieties ‘Tifway’, ‘TifSport’, and ‘TifTuf’, as well as an experimental hybrids (04-76) using a traffic simulator for 6 weeks. Leaf morphology (leaf width, length, and angle) and quantitative measure of density and color [normalized difference vegetation index ratio (NDVI), dark green color index (DGCI), and percent green turf color] were characterized before traffic, and then percent green turf color after 6 weeks of traffic was measured to estimate wear tolerance. ‘TifTuf’ hybrid bermudagrass provided the greatest wear tolerance, as well as the narrowest and shortest leaf lengths, greatest NDVI values and percent green color, and lowest DGCI before traffic. Conversely, 04-76 produced the poorest wear tolerance, as well as the widest and longest leaves, lowest NDVI values and percent green color, and highest DGCI values before traffic. Regression analysis determined that DGCI, leaf length, and leaf width were inversely, or negatively, correlated to wear tolerance, whereas percent green turf color before traffic was directly correlated to wear tolerance. For these hybrids, DGCI had the strongest correlation to increased wear tolerance.

Zoysia japonica Steud. (2n = 4× = 40) is a C4 turfgrass well-adapted for the warm-humid and transitional climatic zones of the USA. Its use is limited to warmer climates because of a relative lack of winter hardiness compared to C3 grasses. Molecular markers associated with this trait would be useful for effective selection of winter hardy germplasm before field testing. A pseudo-F2 mapping population of 175 individuals was developed from crosses between Z. japonica cultivars “Meyer” (freeze-tolerant) and “Victoria” (freeze-susceptible) and used to generate a high-density genetic map of 104 SSR markers and 2359 sequencing-derived SNP markers. The map covers 324 Mbp and 2520 cM as well as the 20 chromosomes for the zoysiagrass haploid genome. Phenotypic data on winter injury, establishment, and turf quality collected in North Carolina and Indiana in 2014–2016 were used in conjunction with this map to identify quantitative trait loci (QTL) associated with winter hardiness. Fifty-six QTL associated with winter injury, establishment, and turf quality were identified over six environments. Twelve of those were identified in two or more environments. Furthermore, seven regions of interest were identified on chromosomes 8, 11, and 13 where co-location of QTL for three or more traits occurred. Within these regions, analysis with NCBI basic local alignment search tool (BLAST) identified proteins related to cold and other abiotic stresses tolerance. These QTL and associated markers could be valuable in implementing marker-assisted selection for winter hardiness in zoysiagrass breeding programs.

Background Interspecific hybrid bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] is one of the most widely used grasses on golf courses, with cultivars derived from ‘Tifgreen’ or ‘Tifdwarf’ particularly used for putting greens. Many bermudagrass cultivars established for putting greens can be genetically unstable and lead to the occurrence of undesirable off-type grasses that vary in phenotype. The objective of this research was to genetically and phenotypically differentiate off-type grasses and hybrid cultivars. Beginning in 2013, off-type and desirable hybrid bermudagrass samples were collected from golf course putting greens in the southeastern United States and genetically and phenotypically characterized using genotyping-by-sequencing and morphology. Results Genotyping-by-sequencing determined that 11% (5) of off-type and desirable samples from putting greens were genetically divergent from standard cultivars such as Champion, MiniVerde, Tifdwarf, TifEagle, and Tifgreen. In addition, genotyping-by-sequencing was unable to genetically distinguish all standard cultivars from one another due to their similar origin and clonal propagation; however, over 90,000 potentially informative nucleotide variants were identified among the triploid hybrid cultivars. Conclusions Although few genetic differences were found in this research, samples harvested from golf course putting greens had variable morphology and were clustered into three distinct phenotypic groups. The majority of off-type grasses in hybrid bermudagrass putting greens were genetically similar with variable morphological traits. Off-type grasses within golf course putting greens have the potential to compromise putting surface functionality and aesthetics.

Contamination of newly planted bermudagrass (Cynodon spp.) varieties by undesirable off-type bermudagrass genotypes is an ever increasing concern for turf managers because selective control options are limited. In 2009, a sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} tolerant bermudagrass genotype (93-175) was identified during herbicide screening at the University of Georgia in Tifton. The objective of this research was to assess the tolerance of 93-175 to three Acetyl-CoA carboxylase (ACCase) herbicides in comparison to the susceptible genotypes Tifway and common bermudagrass. Greenhouse and field trials were performed between August 2011 and April 2013. Factors in the field experiment included ACCase herbicides, application rates, bermudagrass genotypes, and locations. Turfgrass injury ratings taken 42 days after treatment (DAT) and during greenup the following spring supported initial preliminary findings. At the 1x rate of sethoxydim (280 g a.i. ha–¹), 93-175 displayed 50 to 87% less injury in comparison to the susceptible genotypes. In the spring of 2013, 93-175 plots treated with a 1x rate of sethoxydim reached 100% recovery during the same time period as non-treated controls, while common and Tifway had only recovered to 48 and 60%, respectively. The tolerance mechanism of 93-175 to sethoxydim did not confer an appreciable reduction of clethodim {(E,E)-(6)-2-[1-[[(3-chloro-2-propenyl)oxy]imino]propyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} or fluazifop {(6)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl]oxy]phenoxy]propanoic acid} herbicide treatment effects. 93-175 will continue to be studied to determine transferability of herbicide tolerance to progeny and the mechanism of the observed tolerance.

Warm season turf taxa of centipedegrass [Eremochloa ophiuroides (Munro) Hack], bermudagrass [Cynodon L.C. Rich, spp.], St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and zoysiagrass [Zoysia Willd. spp.] were evaluated for tolerance to adult twolined spittlebug (Prosapia bicincta Say) feeding in choice and no-choice experiments, and for their ability to support nymphal development (antibiosis potential). Among 133 selections evaluated, few showed evidence of potential antibiosis and/or improved tolerance over commercially available cultivars. Most of the centipedegrass taxa evaluated were susceptible to the spittlebug. However, some potential antibiosis among Chinese centipedegrass taxa was identified, and there was a gradient in the ability to tolerate spittlebug feeding. Among centipedegrasses, TC 358 and TC 362 showed moderate tolerance and recovery in no-choice and choice trials. The most tolerant bermudagrasses in no-choice trials were 00 - 23, 03 - 14, and 03 - 15. Centipedegra...

Bermudagrass (Cynodon spp.) is the foundation of the turfgrass industry in most tropical and warm-temperate regions. Development of bermudagrass as a turfgrass began in the early 1900s. Many of the cultivars commercially available today have been cooperatively released by the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) and the University of Georgia at the Coastal Plain Experiment Station in Tifton, GA.

Seashore paspalum is a salt tolerant, predominately diploid (2n = 2x = 20) species that is well adapted to coastal regions in tropical and subtropical environments. Because a majority of the available cultivars are propagated vegetatively and most genotypes are cross-fertile, a sterile cultivar that does not produce segregating seedlings would benefit sod growers and turfgrass managers who demand uniformity for certification and performance. Therefore, an experiment was conducted to create a colchicine-induced polyploid seashore paspalum. One triploid (2n = 3x = 30) genotype (11-TSP-1) was identified and remains stable. Although there is a possibility that this event was triggered by the colchicine treatment, a more likely explanation is that it resulted from the union of a reduced and an unreduced gamete. Pollen shed was observed from 11-TSP-1 in 2011, but individual pollen grains stained with iodine–potassium iodide were irregularly shaped and typically had lower starch content than pollen from several diploid cultivars. The leaf width of 11-TSP-1 was statistically equal to that of the seashore paspalum cultivar SeaStar, indicating its potential for use as a fine turf. 11-TSP-1 had both superior visual color and a dark green color index when compared with ‘SeaStar’. Future study of the reproductive fertility and more extensive field testing of this genotype should be carried out to determine its turfgrass potential. Chemical names used: 4′, 6-diamidino-2-phenylindole (DAPI), dimethyl sulfoxide (DMSO), iodine-potassium iodide (I2-KI), propidium iodide (PI).

Zoysiagrasses ( Zoysia Willd.) are a slow-grow - ing, tetraploid (2 n = 4x = 40) turfgrass that can be successfully managed with less input than many other warm-season grasses. Despite extensive genetic and morphological variation, genotypes with the ability to recuperate quickly from damage are rare. Therefore, a long-term effort to increase vegetative growth rates was initiated during 2009 by first studying the effec - tiveness of six colchicine seed treatments and breeding for manipulating the ploidy level of 'Zenith' zoysiagrass. Colchicine-treated seed - lings were screened using flow cytometry for genome size changes. Four putative octaploids and one cytochimera were identified. Average stomata length of the four colchicine-induced putative octaploids were 28% larger than that of Zenith, but the cytochimera's stomata length was not altered. p ollen diameter of the four puta - tive octaploids was larger than that of Zenith and the cytochimera. p ollen stainability was rel - atively unchanged by the colchicine treatments.

Traffic simulators are often utilized when researching turfgrass wear tolerance and recov - ery. However, the availability of a durable traffic simulator capable of producing dynamic force is limited. Therefore, the objectives of this research were to: (i) evaluate a novel traffic simulator with improved durability and capable of producing dynamic force and (ii) evaluate the biophysical effects of the traffic simulator on a native soil turfgrass system. The Baldree traffic simulator is a modified r yan GA 30 (Jacobsen, A Textron Company, Charlotte, NC) riding aerification unit, equipped with fabricated, spring loaded steel plate feet studded with screw in cleats. The effects of this unit on a 'Tifway' bermudagrass (Cynodon dactylon (L.) pers. × C. transvaalen - sis Burtt-Davy) system established on a Tifton loamy sand (fine-loamy, kaolinitic, thermic p- thic Kandiudults) were evaluated at the Coastal plains Experiment Station, Tifton, GA. Factors included location (1 and 2) and traffic rate (0, 12, and 24 passes applied over a 6 wk period). Field data included soil bulk density, turf density, and percent green turf cover. An in-ground force plate at the Mcphail Equine performance Center, East Lansing, MI was used to quantify vertical and net shear ground reaction force produced by the Baldree traffic simulator when operated in the forward and backward direction. The Baldree traffic simulator produced more cleat marks per pass than the Brinkman and Cady traffic simulators. At the low traffic rate the Bal - dree traffic simulator increased soil bulk density, while turf density and percent green turf cover decreased; therefore, the tool can be used to simulate heavy traffic conditions with a minimum number of passes.

Ornamental grasses such as fountaingrass or napiergrass, collectively called pennisetums, belong to the genus Pennisetum, which is a diverse genus with over 80 species adapted to a wide range of climatic regions and known for its drought tolerance. Breeding efforts have led to improvements such as more intense purple foliage color, disease resistance, and apparent sterility. These improved forms have been developed and tested in the eastern United States. The objective of this research was to evaluate container and field performance of seven new complex hybrid pennisetums in the Pacific northwestern United States. Two completely randomized experiments with three replications were conducted over 2 years (2010 and 2011) at two locations. We selected seven trispecific hybrid pennisetums resulting from interploid and interspecific crossing that were given accessions Tift 5, Tift 6, Tift 10, Tift 11, Tift, 13, Tift 15, and Tift 26. Experiment 1 evaluated container performance in Corvallis, OR, while Expt. 2 evaluated field performance in Aurora, OR. Size index (SI), growth form rating, and color rating were collected and analyzed separately by location. In the container study, significant differences were observed among selections for growth form in 2010 and color ratings in both 2010 and 2011. In 2010, Tift 6, Tift 11, Tift 13, and Tift 15 had the highest growth form rating. For color rating, Tift 5, Tift 10, and Tift 26 were among the four highest rated selections in both years. In the field study, Tift 5, Tift 10, Tift 11, and Tift 26 had the highest SI when data were pooled over the 2 years, but all selections reached acceptable size for landscape use during both years of the study. Similarly, there were color differences among selections with Tift 5, Tift 10, Tift 15, and Tift 26 being highest rated. None of the selections survived below winter temperatures of −5 °C at either location during either year of the study. Our evaluations indicate that these selections have potential in the Pacific northwestern United States as annuals. Differences in complex hybrid pennisetums were observed in SI, growth form rating, and color rating. These differences demonstrated the variation among selections and will allow producers to choose desired traits based on market preference.

We report SSR-enriched genetic maps of bermudagrass that: (1) reveal partial residual polysomic inheritance in the tetraploid species, and (2) provide insights into the evolution of chloridoid genomes. This study describes genetic linkage maps of two bermudagrass species, Cynodon dactylon (T89) and Cynodon transvaalensis (T574), that integrate heterologous microsatellite markers from sugarcane into frameworks built with single-dose restriction fragments (SDRFs). A maximum likelihood approach was used to construct two separate parental maps from a population of 110 F1 progeny of a cross between the two parents. The T89 map is based on 291 loci on 34 cosegregating groups (CGs), with an average marker spacing of 12.5 cM. The T574 map is based on 125 loci on 14 CGs, with an average marker spacing of 10.7 cM. Six T89 and one T574 CG(s) deviated from disomic inheritance. Furthermore, marker segregation data and linkage phase analysis revealed partial residual polysomic inheritance in T89, suggesting that common bermudagrass is undergoing diploidization following whole genome duplication (WGD). Twenty-six T89 CGs were coalesced into 9 homo(eo)logous linkage groups (LGs), while 12 T574 CGs were assembled into 9 LGs, both putatively representing the basic chromosome complement (x = 9) of the species. Eight T89 and two T574 CGs remain unassigned. The marker composition of bermudagrass ancestral chromosomes was inferred by aligning T89 and T574 homologs, and used in comparisons to sorghum and rice genome sequences based on 108 and 91 significant blast hits, respectively. Two nested chromosome fusions (NCFs) shared by two other chloridoids (i.e., zoysiagrass and finger millet) and at least three independent translocation events were evident during chromosome number reduction from 14 in the polyploid common ancestor of Poaceae to 9 in Cynodon.