Evaluation of Off-Type Grasses in Interspecific Hybrid Bermudagrass [\u3ci\u3eCynodon dactylon\u3c/i\u3e (L.) Pers. x \u3ci\u3eC. transvaalensis\u3c/i\u3e Burtt-Davy] Putting Greens

The economic impact of the golf industry in the United States (U.S.) in 2011 was estimated to be $176.8 billion. Interspecific hybrid bermudagrasses [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] are some of the most widely utilized grasses on golf courses throughout tropical, subtropical, and temperate climates. In 2007, bermudagrass was grown on 80% of putting green acreage in the southern U.S. ‘Tifgreen’ and ‘Tifdwarf’ were two of the first widely established cultivars on putting greens, but their genetic instability led to the occurrence of phenotypically different off-type (OT) grasses. Several OT grasses were selected and released as cultivars such as ‘Champion’, ‘MiniVerde’, and ‘TifEagle’. These cultivars can also be genetically unstable and OT grasses can occur in putting greens. The objectives of this research were to genetically and phenotypically characterize OT grasses and evaluate their responses to nitrogen (N) and trinexapac-ethyl (TE) applications. Off-type and desirable bermudagrass samples were collected from Champion, MiniVerde, and TifEagle golf course putting greens in 2013 and 2014. Grasses were genetically evaluated using genotyping-by-sequencing (GBS), which determined that 11% were genetically divergent from standard cultivars. Off-types were phenotypically characterized using morphology and samples clustered into three distinct morphological groups that varied in internode length and leaf length. The response of OT grasses and cultivars to six N and eight TE treatments was evaluated by measuring clippings 7, 14, 21, and 28 days after initial treatment (DAIT). The least three N rates decreased weekly clipping production 18 to 29% [percent], whereas the greatest three rates sustained growth. We observed that peak growth regulation occurred 21 DAIT for the majority of TE rates tested where clipping weights decreased 18 to 35% from 7 to 21 DAIT. We also observed a period of increased clipping production 18 to 47% from 21 to 28 DAIT for all grasses tested. It is important to maintain consistent growth among phenotypically different grasses in order to minimize any competitive growth advantage an OT grass may possess over a desirable cultivar in a golf course putting green

Water-Use Characteristics of Warm-Season Putting Green Cultivars and Management Practices Associated with New Putting Green Genetics

Bermudagrass (Cynodon spp.) is the most common turfgrass used on golf course putting greens in the southeastern United States (Lyman et al., 2007). In 2013, the National Turfgrass Evaluation Program (NTEP) started a 5-year trial of warm-season putting green cultivars. One of the bermudagrass cultivars in the study is MSB-285 (experimental cultivar). MSB-285 is a sister plant of MSB-264 (Philley and Munshaw, 2011) and is a distinct cultivar of C. dactylon × C. transvaalensis. MSB-285 has a more extensive root system and upright growth habit than traditional bermudagrass putting green cultivars (Philley and Munshaw, 2011). Due to MSB-285’s unique genetic makeup and growth habit, the objectives of this research were to determine if best management practices used to maintain ultradwarf bermudagrasses would be suitable for MSB-285 and to determine the water-use characteristics of MSB-285 compared to industry standard cultivars

Water-Use Characteristics of Warm-Season Putting Green Cultivars and Management Practices Associated with New Putting Green Genetics

Bermudagrass (Cynodon spp.) is the most common turfgrass used on golf course putting greens in the southeastern United States (Lyman et al., 2007). In 2013, the National Turfgrass Evaluation Program (NTEP) started a 5-year trial of warm-season putting green cultivars. One of the bermudagrass cultivars in the study is MSB-285 (experimental cultivar). MSB-285 is a sister plant of MSB-264 (Philley and Munshaw, 2011) and is a distinct cultivar of C. dactylon × C. transvaalensis. MSB-285 has a more extensive root system and upright growth habit than traditional bermudagrass putting green cultivars (Philley and Munshaw, 2011). Due to MSB-285’s unique genetic makeup and growth habit, the objectives of this research were to determine if best management practices used to maintain ultradwarf bermudagrasses would be suitable for MSB-285 and to determine the water-use characteristics of MSB-285 compared to industry standard cultivars

EC70-178 Lawn Weeds and their Control

Extension Circular 70-178: Lawn weeds and their control; description of different types of weeds and their control. Also published as North Central Regional Extension Publication No. 2

EC76-178 Lawn Weeds and their Control

Extension Circular 76-178 discusses lawn weeds and their control. Also published as : North Central Regional Extension Publication No. 2

Using Covers and Wetting Agents to Prevent Winter Injury of Ultradwarf Bermudagrass

As ultradwarf bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) putting green use in the United States moves further north, there is risk of sustaining winter injury from low-temperature exposure and tissue desiccation. Protective covers reduce low-temperature exposure on ultradwarf bermudagrass greens. Desiccation of turf can be caused by hydrophobic soils. Wetting agents are applied to actively growing ultradwarf bermudagrass greens to relieve symptoms of hydrophobic soils. Less is known about the effects late-fall wetting agent applications on dormant bermudagrass putting greens. This research aims to define a predicted low-temperature threshold for covering ultradwarf bermudagrass greens and to quantify the effects of a late-fall wetting agent application on winter survival of ultradwarf bermudagrass. A protective cover and wetting agent trial was conducted on a sand-based putting green with plots of ‘Champion’, ‘MiniVerde’, and ‘TifEagle’ ultradwarf bermudagrass during the winters if 2015-2016 and 2016-2017. Cover treatments were placed at forecasted low-temperature thresholds of -9.4, -7.8, -5.6, and -4.0 °C and were compared to an uncovered control. A single late-fall wetting agent application was applied to each cultivar x cover treatment. An additional wetting agent trial was conducted by comparing a single application of various wetting agent treatments to an untreated control on a sand-based ultradwarf bermudagrass putting green. Spring green-up was monitored by quantifying green turfgrass coverage through digital image analysis. Soil volumetric water content was monitored at a depth of 3.8 cm using time-domain reflectometry. The wetting agent trial included two water drop penetration tests during each season. In both seasons, reducing the cover temperature threshold resulted in significant differences in green turfgrass coverage between treatments, but lower cover temperatures did not delay green-up of turf. ‘MiniVerde’ and ‘TifEagle’ greened up significantly faster compared to ‘Champion’. In 2016, wetting agent treatments greened up significantly faster than the untreated control. Multiple wetting agent treatments significantly reduced water drop penetration times in the top three cm of the soil profile. Our research demonstrates the potential to reduce the forecasted low-temperature for covering ultradwarf bermudagrass without negatively impacting turf health, potentially reducing golf course winter labor costs

EC68-178 Lawn Weeds and their Control

Extension Circular 68-178: Lawn Weeds and their control; identification and descriptions, control methods such as chemical control or mechanical control

Genome-wide association study for agronomic traits in bermudagrass (Cynodon spp.)

Bermudagrass (Cynodon spp.) breeding and cultivar development is hampered by limited information regarding its genetic and phenotypic diversity. A germplasm collection of 206 bermudagrass accessions from 29 countries was genotyped with high-throughput genotyping-by-sequencing technique. Genomic diversity in this diverse germplasm panel was assessed with multifaceted approaches including population structure, phylogenetic analysis, principal component analysis, and genetic diversity parameters. This study revealed substantial genetic variation in the Cynodon accessions, demonstrating the potential of this germplasm panel for further genetic studies and cultivar development in breeding programs. Another critical issue in turfgrass breeding is the lack of information regarding the genetic architecture of traits. Four agronomic traits leaf length, leaf width, internode distance and stem diameter were evaluated in a germplasm panel of common bermudagrass accessions. Then genome-wide association study was performed to dissect the genetic basis of the traits

Etiology and Epidemiology of Mini-ring in Ultradwarf Bermudagrass Putting Greens

Mini-ring is a disease in ultradwarf bermudagrass (UDBG) [Cynodon dactylon (L.) Pers. × C. transvaalensis (Burtt-Davy)] putting greens caused by Waitea zeae (Voorhees) J.A. Crouch & Cubeta, (formerly Rhizoctonia zeae). Symptoms typically resemble frog-eye patches that are 10 to 40 cm in diameter with a bronze to orange outer ring and green center. In the southeastern United States, mini-ring symptoms appear in late-summer and generally persist until UDBG dormancy in late-fall. Mini-ring is often problematic in UDBG when nitrogen (N) fertility is reduced to manage organic matter production and improve putting green performance and perceived green speed. While W. zeae is most frequently reported as the causal agent, other species of Waitea have been isolated from UDBG exhibiting mini-ring symptoms. Waitea zeae causes visible leaf lesions and basal sheath rot in other turfgrasses; however, in UDBG, dieback of leaf tissue occurs in the absence of leaf lesions and sheath rot. Although W. zeae has been isolated from UDBG leaf tissue throughout the growing season, it is unclear if other plant tissues—e.g., root, rhizomes, and stolons—may be possible infection courts and when W. zeae infection most likely occurs. The objectives of these studies were to: I) investigate the impact of N source and N rate on mini-ring disease development and severity in UDBG; II) determine what plant tissues W. zeae can infect and when infection is most likely to occur; and III) collect and characterize isolates of Waitea spp. recovered from symptomatic UDBG putting greens. To study the impact of N on mini-ring disease severity, ammonium sulfate (AMS) [(NH4)2SO4] and urea (CH4N2O) were applied weekly to ‘P18’ (MiniVerde) and ‘TifEagle’ UDBG at rates of 4.9, 9.8, and 14.7 kg N ha-1. Mini-ring severity increased with increasing rates of AMS whereas disease symptoms in plots treated with urea remained relatively low. Cores from a UDBG putting green located in Florence, SC were collected monthly from June to October in 2016 and 2017. Isolation of W. zeae occurred in all months, isolation frequencies were greatest in August and September. In a growth chamber bioassay, UDBG roots, stolons, and leaves were infected by W. oryzae or W. zeae when inoculum when growing medium was infested with representative isolates. Nineteen Waitea species isolates were recovered from UDBG putting greens expressing mini-ring symptoms in North Carolina and South Carolina. Isolates of W. prodiga, W. oryzae, and W. zeae represented 5, 16, 79% of isolates collected. Isolates were characterized by sequencing the rDNA-internal transcribed spacer region, and these sequences clustered with Waitea species isolate sequences deposited in GenBank and previously described. These studies demonstrate the primary causal agent of mini-ring in UDBG is W. zeae, while other species of Waitea are likely involved to a lesser extent. An effective mini-ring management strategy should include regular N applications using N sources other than AMS, such as urea, to promote UDBG growth and recuperative potential and applications of fungicides mid-summer before symptom development. Fungicides should be applied in a manner that encourages movement of active ingredients into the putting green rootzone to reduce W. zeae infection of UDBG roots and stolons

Genetic diversity and population structure of bermudagrass (Cynodon spp.) revealed by genotyping-by-sequencing

Bermudagrass (Cynodon spp.) breeding and cultivar development is hampered by limited information regarding its genetic and phenotypic diversity. To explore diversity in bermudagrass, a total of 206 Cynodon accessions consisting of 193 common bermudagrass (C. dactylon var. dactylon) and 13 African bermudagrass (C. transvaalensis) accessions of worldwide origin were assembled for genetic characterization. Genotyping-by-sequencing (GBS) was employed for genetic marker development. With a minor allele frequency of 0.05 and a minimum call rate of 0.5, a total of 37,496 raw single nucleotide polymorphisms (SNPs) were called de novo and were used in the genetic diversity characterization. Population structure analysis using ADMIXTURE revealed four subpopulations in this germplasm panel, which was consistent with principal component analysis (PCA) and phylogenetic analysis results. The first three principal components explained 15.6%, 10.1%, and 3.8% of the variance in the germplasm panel, respectively. The first subpopulation consisted of C. dactylon accessions from various continents; the second subpopulation was comprised mainly of C. transvaalensis accessions; the third subpopulation contained C. dactylon accessions primarily of African origin; and the fourth subpopulation represented C. dactylon accessions obtained from the Oklahoma State University bermudagrass breeding program. Genetic diversity parameters including Nei’s genetic distance, inbreeding coefficient, and Fst statistic revealed substantial genetic variation in the Cynodon accessions, demonstrating the potential of this germplasm panel for further genetic studies and cultivar development in breeding programs