Ecological restoration and biodiversity-friendly management of urban grasslands - A global review on the current state of knowledge.

In the face of the global biodiversity decline, ecological restoration measures to actively enhance urban biodiversity and options for biodiversity-friendly greenspace management are high on the agenda of many governments and city administrations. This review aims to summarize and advance the current knowledge on urban grassland restoration by synthesizing research findings on restoration approaches and biodiversity-friendly management measures globally. Indeed, we found restoration approaches to be generally effective in increasing biodiversity; yet, there were variations in the outcomes due to the difference in soil disturbance methods, management regimes, the set of species introduced to a site, and the specific local setting. Based on the reviewed studies, we formulated recommendations for maximizing restoration success of urban grasslands through: i) creating a network of heterogeneous urban greenspaces and enhancing connectivity between them; ii) maintaining the spontaneous vegetation in vacant lots and wasteland sites that can provide habitats for various invertebrate species; iii) evaluating actual soil conditions, soil seed bank, and seed rain before restoration efforts take place since these seed sources could considerably affect the restoration outcomes, iv) preserving nutrient-poor conditions in urban greenspaces instead of introducing nutrient-rich topsoil; v) shifting to less intensive, biodiversity-friendly management in urban greenspaces by reducing mowing frequency and avoiding the use of chemicals; and vi) utilizing native dry grassland species for climate adaptation without irrigation. We further identified knowledge gaps regarding i) city-scale and regional-scale effects of restoration, ii) effects of interventions on multiple taxa and multiple ecosystem services, iii) restoration in small versus mega-cities, and iv) in the global south. These gaps should be addressed in future studies for making general guidelines for urban grassland restoration broadly applicable.

Comparative Physiological and Gene Expression Analyses Reveal Mechanisms Involved in Maintaining Photosynthesis Capacity, Alleviating Ion Toxicity and Oxidative Stress of Kentucky Bluegrass under NaCl Treatment.

Kentucky bluegrass (Poa pratensis L.), a widely used cool-season turfgrass, shows a high sensitivity to soil salinity. Clarifying the adaptative mechanisms of Kentucky bluegrass that serve to improve its salt tolerance in saline environments is urgent for the application of this turfgrass in salt-affected regions. In this study, physiological responses of the Kentucky bluegrass cultivars "Explorer" and "Blue Best" to NaCl treatment, as well as gene expressions related to photosynthesis, ion transport, and ROS degradation, were analyzed. The results showed that the growth of "Explorer" was obviously better compared to "Blue Best" under 400 mM NaCl treatment. "Explorer" exhibited a much stronger photosynthetic capacity than "Blue Best" under NaCl treatment, and the expression of key genes involved in chlorophyll biosynthesis, photosystem II, and the Calvin cycle in "Explorer" was greatly induced by salt treatment. Compared with "Blue Best", "Explorer" could effectively maintain Na+/K+ homeostasis in its leaves under NaCl treatment, which can be attributed to upregulated expression of genes, such as HKT1;5, HAK5, and SKOR. The relative membrane permeability and contents of O2- and H2O2 in "Explorer" were significantly lower than those in "Blue Best" under NaCl treatment, and, correspondingly, the activities of SOD and POD in the former were significantly higher than in the latter. Moreover, the expression of genes involved in the biosynthesis of enzymes in the ROS-scavenging system of "Explorer" was immediately upregulated after NaCl treatment. Additionally, free proline and betaine are important organic osmolytes for maintaining hydration status in Kentucky bluegrass under NaCl treatment, as the contents of these metabolites in "Explorer" were significantly higher than in "Blue Best". This work lays a theoretical basis for the improvement of salt tolerance in Kentucky bluegrass.

The Impact of Wildflower Habitat on Insect Functional Group Abundance in Turfgrass Systems.

Urbanization is rapidly influencing the abundance and diversity of arthropods. Within urban systems, managed turfgrass is a prominent land cover which can support only a limited number of arthropod groups. To allow for more arthropod biodiversity and to support beneficial insects within turfgrass, increasing numbers of land managers are choosing to partially convert turf habitat to wildflower habitat using commercially available seed mixes. However, the population dynamics of arthropod groups in these systems are poorly known, with consequentially little information on best long-term practices for managing wildflower habitats in turfgrass systems. To address this gap, we sampled insects using pan traps in turfgrass systems pre- and post-implementation of wildflower habitats and examined the change in abundance of several insect families and functional guilds. Insect groups had variable responses to wildflower habitat implementation, with some groups such as sweat bees and skipper butterflies showing a decline two years post-implementation. Other groups, such as predatory flies, were relatively more abundant one and two years post-implementation. These variable responses point to the need for more research on the long-term effects of wildflower habitats on beneficial insects in turfgrass habitats.

Inducible defense phytohormones in annual bluegrass (Poa annua) and creeping bentgrass (Agrostis stolonifera) in response to annual bluegrass weevil (Listronotus maculicollis) infestation.

The annual bluegrass weevil (Listronotus maculicollis) is the most damaging insect pest of short-mown turfgrass on golf courses in eastern North America. Listronotus maculicollis larvae cause limited visible damage as stem-borers (L1-3), compared to the crown-feeding (L4-5) developmental instars. Prolonged larval feeding results in discoloration and formation of irregular patches of dead turf, exposing soil on high-value playing surfaces (fairways, collars, tee boxes, and putting greens). Annual bluegrass (Poa annua) is highly susceptible to L. maculicollis compared to a tolerant alternate host plant, creeping bentgrass (Agrostis stolonifera). This study explored whether defense signaling phytohormones contribute to A. stolonifera tolerance in response to L. maculicollis. Concentrations (ng/g) of salicylic acid (SA), jasmonic acid (JA), jasmonic-isoleucine (JA-Ile), 12-oxophytodienoic acid (OPDA), and abscisic acid (ABA) were extracted from turfgrass (leaf, stem, and root) tissue samples as mean larval age reached 2nd (L2), 3rd (L3), and 4th (L4) instar. Poa annua infested with L. maculicollis larvae (L2-4) possessed significantly greater SA in above-ground tissues than A. stolonifera. Levels of constitutive JA, JA-Ile, OPDA, and ABA were significantly higher within non-infested A. stolonifera aboveground tissues compared to P. annua. Inducible defense phytohormones may play a role in P. annua susceptibility to L. maculicollis but are unlikely to provide tolerance in A. stolonifera. Additional studies in turfgrass breeding, particularly focusing on cultivar selection for increased constitutive JA content, could provide a non-chemical alternative management strategy for L. maculicollis for turfgrass managers.

Persulfate photolysis and limited irrigation of recycled wastewater for turfgrass growth: Accumulation of pharmaceutical and personal care products and physiological responses.

Recycled wastewater effluent irrigation and implementing limited irrigation rates are two promising strategies for water conservation in agriculture. However, one major challenge is the accumulation and translocation of Pharmaceutical and Personal Care Products (PPCPs) from recycled water to crops. This study investigated the effects of UV persulfate (UV/PS) treatment of recycled water and limited irrigation rate on PPCPs accumulation and physiological responses of St. Augustine turfgrass via a 14-week field trial. Carbamazepine (CBZ), sulfamethoxazole (SMX), triclosan (TCS), fluoxetine (FLX) and diclofenac (DCF) were spiked at 0.1-1.5 µg/L into recycled water and two limited irrigation rates corresponding to 60 % and 80 % of reference Evapotranspiration (ETo) were applied. Results showed that UV/PS removed 60 % of CBZ and > 99 % of other PPCPs from recycled water. Irrigation with UV/PS treated recycled water resulted in approximately a 60 % reduction in CBZ accumulation and complete removal of SMX, DCF, FLX and TCS in both turfgrass leaves and roots. A more limited irrigation rate at 60 % ETo resulted in a higher accumulation of CBZ accumulation compared to 80 % ETo. Similarly, the canopy temperature increased under 60 % ETo irrigation rate compared to 80 % ETo, suggesting that turfgrass under 60 % ETo was more prone to water stress. Applying a 60 % ETo irrigation rate was not sufficient to maintain the turfgrass quality in the acceptable range. A negative correlation between the visual quality and cumulative mass of PPCPs in turfgrass leaves at different irrigation rates was observed, yet irrigation rate was the major driver of turfgrass overall quality and health. Insights from this study will help to integrate recycled water with treatment and limited irrigation, thereby enhancing agricultural water reuse practices.

Using organic amendments in disturbed soil to enhance soil organic matter, nutrient content and turfgrass establishment.

Disturbed soils, including manufactured topsoils, often lack physical and chemical properties conducive to vegetation establishment. As a result, efforts to stabilize disturbed soils with vegetation are susceptible to failure. Urban organic waste products such as wood mulch, composted leaf and yard waste, and biosolids are widely distributed as organic amendments that enhance sustainability and plant establishment. Correct use can be determined by examining soil properties such as pH; the concentration of soluble salts (SS); and plant available nutrients - particularly N, C and P; as well as root and shoot growth. This research examined the effects of three typical organic amendments on fertility, establishment, and nutrient loss. A manufactured topsoil was used as the base soil for all treatments, including a control unamended soil (CUT), and soil amended with either mulch (MAT), composted leaf and yard waste (LAT), or biosolids (BAT). A 2 % organic matter concentration increase was sought but not achieved due to difficulty in reproducing lab results at a larger scale. Results showed that LAT improved soil fertility, particularly N-P-K concentrations while maintaining a good C:N ratio, pH, and SS concentration. BAT was the most effective at enhancing shoot growth but results suggest that improved growth rates could result in increased maintenance. Additionally, biosolids were an excellent source of nutrients, especially N-P-K and S, but diminished root growth and N leachate losses indicate that N was applied in excess of turfgrass requirements. Therefore, biosolids could be used as fertilizer, subject to recommended rates for turfgrass establishment to prevent poor root growth and waterborne N pollution. To ensure establishment efforts are successful, MAT is not recommended without a supplemental source of soluble N. Altogether, study results and conclusions could inform others seeking to improve specifications for disturbed soil where turfgrass establishment is needed to stabilize soil.

Plant-Parasitic Nematode Genera Associated with Turfgrass in Maryland Golf Courses and Athletic Fields.

Field surveys were conducted to assess the occurrence and diversity of plant-parasitic nematodes (PPNs) in golf courses and athletic fields across Maryland, USA, during 2022 and 2023. A total of 28 golf courses and ten athletic fields were surveyed, revealing the prevalence and abundance of 13 PPNs taxa in the region. Criconemoides was identified as the most prevalent (94.9%) and Tylenchorhynchus as the most abundant (2.3) across all samples. Central golf courses (west side of the Chesapeake Bay) exhibited a high prevalence of Criconemoides and Tylenchorhynchus, while Eastern Shore golf courses and athletic fields displayed a higher prevalence of Helicotylenchus and Criconemoides. Further, Belonolaimus longicaudatus was reported for the first time from turfgrass in Maryland, raising concerns due to its potential to cause severe damage on both cool- and warm-season turfgrass. Biodiversity analysis indicated that richness (R2) was higher in athletic fields, while diversity (H') and evenness (J') were significantly greater in golf courses. This study provides baseline information for monitoring PPNs distribution in Maryland and also for the development of effective nematode management approaches in turfgrass ecosystems.

Probe-based loop-mediated isothermal amplification assay for rapid detection of two Clarireedia spp., the causal agent of dollar spot of turfgrass.

Dollar spot is a major fungal disease affecting turfgrass worldwide and can quickly destroy turfgrass swards. An assimilating probe-based loop-mediated amplification (LAMP) assay was developed to detect Clarireedia monteithiana and C. jacksonii, the causal agents of dollar spot within the continental US. Five LAMP primers were designed to target the calmodulin gene with the addition of a 6-carboxyl-fluorescein florescent assimilating probe and the temperature amplification was optimized for C. jacksonii and C. monteithiana identification. The minimum amount purified DNA needed for detection was 0.05 ng µL-1. Specificity assays against host DNA and other turfgrass pathogens were negative. Successful LAMP amplification was also observed for dollar spot infected turfgrass field samples. Further, a DNA extraction technique via rapid heat-chill cycles and visualization of LAMP results via a florescent flashlight was developed and adapted for fast, simple and reliable detection in 1.25 hours. This assimilating probe-based LAMP assay has proved successful as a rapid, sensitive, and specific detection of C. monteithiana and C. jacksonii in pure cultures and from symptomatic turfgrass leaves blades. The assay represents a promising technology to be used in the field for on-site, point-of-care pathogen detection.

Removing grass clippings reduces bermudagrass mite (Acari: Eriophyidae) infestation during turfgrass regrowth.

Bermudagrass mite (Aceria cynodoniensis Sayed) infestation stunts bermudagrass (Cynodon spp. [Poales: Poaceae]) growth, leading to thinned turf and lower aesthetic and recreational value. Bermudagrass mites cause characteristic symptoms called witch's brooms, including shortened internodes and leaves and the proliferation of tillers. Grass clippings produced by mowing or scalping bermudagrass harbor mites, which abandon the desiccating grass clippings and spread to surrounding turfgrass. Dropped grass clippings can lead to infestation of new turfgrass. Nursery experiments were conducted with potted bermudagrass to determine the effect of removing witch's brooms or grass clippings after scalping on witch's broom densities on the recovering bermudagrass. Additionally, laboratory experiments were conducted to assess the potential for mites to abandon detached witch's brooms and to evaluate mite survival after leaving their hosts. The number of initial witch's brooms and individually removing witch's brooms did not affect subsequent witch's broom densities, suggesting that infested but asymptomatic terminals later developed into witch's brooms. Removing grass clippings after scalping reduced witch's broom densities by over 65% in two trials. Most mites (96%) abandoned witch's brooms within 48 h after detaching witch's brooms, and adult mites survived an average of 5.6 h after removal from the host plant. Removing clippings after scalping may improve bermudagrass mite management and limit damage on the recovering turfgrass. Additionally, clippings resulting from regular mowing or scalping should be disposed of properly because this study demonstrates that mites abandon desiccating host plants and survive sufficiently long to infest surrounding turfgrass.

Chromosome-scale genome assembly of Poa trivialis and population genomics reveal widespread gene flow in a cool-season grass seed production system.

Poa trivialis (L.) is a cool-season grass species found in various environments worldwide. In addition to being a desired turfgrass species, it is a common weed of agricultural systems and natural areas. As a weed, it is an important contaminant of commercial cool-season grass seed lots, resulting in widespread gene flow facilitated by human activities and causing significant economic losses to farmers. To better understand and manage infestations, we assembled and annotated a haploid genome of P. trivialis and studied troublesome field populations from Oregon, the largest cool-season grass seed producing region in the United States. The genome assembly resulted in 1.35 Gb of DNA sequence distributed among seven chromosome-scale scaffolds, revealing a high content of transposable elements, conserved synteny with Poa annua, and a close relationship with other C3 grasses. A reduced-representation sequencing analysis of field populations revealed limited genetic diversity and suggested potential gene flow and human-assisted dispersal in the region. The genetic resources and insights into P. trivialis provided by this study will improve weed management strategies and enable the development of molecular detection tests for contaminated seed lots to limit seed-mediated gene flow. These resources should also be beneficial for turfgrass breeders seeking to improve desirable traits of commercial P. trivialis varieties and help to guide breeding efforts in other crops to enhance the resiliency of agricultural ecosystems under climate change. Significance Statement: The chromosome-scale assembly of Poa trivialis and population genomic analyses provide crucial insights into the gene flow of weedy populations in agricultural systems and contribute a valuable genomic resource for the plant science community.

Depth distribution of plant-parasitic nematodes on bentgrass golf greens in Missouri and Indiana.

Control of plant-parasitic nematodes (PPNs) on golf putting greens with nematicides is dependent on the seasonal occurrence and depth distribution of target PPN populations. This study aimed to determine if plant-parasitic nematode populations on golf course putting greens in Missouri and Indiana peaked at a targetable depth at a specific time in the year, focusing primarily on lance (Hoplolaimus spp.) and root-knot (Meloidogyne spp.) nematodes. To elucidate species diversity in the region, rDNA from a subset of lance and root-knot nematodes was sequenced and analyzed, with additional micromorphology of a lance nematode assessed in scanning electron micrographs (SEM). Soil samples were taken to a depth of 25 cm and stratified into 5 cm increments during April, June, August and October at seven sites across Missouri, three in the Kansas City metro of Kansas in 2021 and in ten sites across Indiana in 2022. Samples were stratified in five-centimeter increments and aggregated for a total of 100 cm3 of soil at each depth for each sampling. Samples were processed using a semi-automatic elutriator followed by the sucrose-flotation method, and populations were counted using a hemocytometer and recorded. For molecular characterization, rDNA was extracted and analyzed from 31 individual lance nematodes from one site in Missouri and eight sites in Indiana, and 13 root-knot nematodes from nine sites across Indiana. A significant interaction occurred between sampling month and depth for lance and ring nematodes Missouri/KS, with both PPN populations peaking at the 0-5 cm depth during October, which is well after most targeted nematicide applications are applied. Ring nematodes in Indiana did not follow this trend and were most abundant in August at a depth of 0-5 cm. No significant interaction between depth and month occurred for lance or root-knot nematodes in Indiana, or root-knot nematodes in Missouri/KS. Hoplolaimus stephanus and H. magnistylus were the lance species identified on golf greens, and Meloidogyne naasi, M. graminicola and M. marylandi were the root-knot species identified. Scanning-electron micrographs confirmed morphological characteristics unique to H. stephanus.

Dose-dependent physiological effects of UV-C radiation on seashore paspalum.

Positive effects of ultraviolet-C (UV-C) radiation on plants have been documented in previous literature with a focus on extending shelf life and reducing disease development. However, its effect on plant growth habits has been scarcely explored, especially in turfgrass where a compact shoot growth is a desirable trait. Seashore paspalum (Paspalum vaginatum) is a warm-season perennial turfgrass requiring low fertilizer and pesticide inputs. This project aimed to test the effects of different doses of UV-C radiation on growth and performance of seashore paspalum cv. Seastar. Here, we provide evidence of dose-dependent effects. Lower UV-C doses (6 s and 1 min daily) improved the performance of seashore paspalum, as manifested by higher tiller density, reduced clipping yields, increased chlorophyll level on selected dates as well as enhanced photosynthetic efficiency compared to control. Contrastingly, higher doses (6 min and 30 min daily) resulted in severe damage with 30-min treatment being lethal to seashore paspalum, causing marked declines in all measured parameters. This is the first time that UV-C-induced growth response was reported in turf. Conclusions drawn from this study would shed light into the effects of UV-C radiation on the growth and performance of seashore paspalum and offer exciting potential for the utilization of UV-C at non-lethal dosage in turfgrass management.

Long-term fertilization and cultivation impacts on nematode abundance and community structure in tall fescue turfgrass.

Impacts of long-term fertilization and cultivation were evaluated on nematode communities associated with tall fescue turfgrass following 11 years of treatment applications. Fertilizer treatments of biosolid, synthetic, and plant-based fertilizers and cultivation treatments of 0×, 1×, and 2× aerification passes were applied to randomized and replicated tall fescue plots at the University of Maryland Paint Branch Turfgrass facility in College Park, Maryland. Free-living and plant-parasitic nematodes were identified, enumerated, and categorized into functional groups. Nematode count data were compared using generalized linear mixed modeling with negative binomial distribution and two-way ANOVA was used to compare nematode ecological indices. Biosolid treatments resulted in lower omnivore-predator densities than plant-based fertilizer treatments (p ≤ .001) and significantly greater Hoplolaimus densities than plant-based fertilizer plots (p ≤ .05). Synthetic fertilizer applications resulted in the greatest Eucephalobus (p ≤ .05) and total bacterivore densities (p ≤ .001) of all fertilizer treatments. Plant-based fertilizer-treated plots had the largest Maturity Index cp 2-5 and Structure Index (p ≤ .05). Cultivation of 1× resulted in fewer total bacterivore densities than 2× (p ≤ .01) while omnivore-predator densities were greater in 1× than 0× (p ≤ .001). Plant health, as measured by NDVI, was lowest in biosolid-treated turfgrass (p ≤ .05). These findings suggest that long-term turfgrass management practices can have variable impacts on nematode abundance and community structure in tall fescue and provide insights into ecological impacts of turfgrass management practices.

Persistence of Fungicides Applied to Control Snow Mold of Turfgrass as Influenced by Snow Cover and Antitranspirants.

Turfgrass managers rely on fungicides to suppress snow mold diseases in areas with persistent snow cover, which are commonly applied once or twice in late fall prior to snow cover. Fungicide applications targeting snow mold are expected to control snow mold diseases for the duration of winter; however, climate change is increasing the frequency of winter rainfall and snowmelts and may alter the duration of snow mold control. A 3-year study was conducted in Madison, WI, to assess the impact of snow cover and antitranspirants on the persistence of the commonly used fungicides chlorothalonil and propiconazole. Snow cover, fungicide treatment, and the use of antitranspirants had minimal impacts on fungicide persistence and disease control. The most important factors influencing persistence of the fungicides were snowmelt and winter rainfall events, yet antitranspirants demonstrated modest evidence of extending chlorothalonil persistence in certain years. These results demonstrate that increasing snowmelt and winter rainfall events associated with climate change will increase dissipation of fungicides used for snow mold suppression, which will likely impact disease control.[Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Environmental and Edaphic Factors that Influence Spring Dead Spot Epidemics.

Spring dead spot (SDS) (Ophiosphaerella spp.) is a soilborne disease of warm-season turfgrasses grown where winter dormancy occurs. The edaphic factors that influence where SDS epidemics occur are not well defined. A study was conducted during the spring of 2020 and repeated in the spring of 2021 on four 'TifSport' hybrid bermudagrass (Cynodon dactylon × transvaalensis) golf course fairways expressing SDS symptoms in Cape Charles, VA, U.S.A. SDS within each fairway was mapped from aerial imagery collected in the spring of 2019 with a 20 MP CMOS 4k true color sensor mounted on a DJI Phantom 4 Pro drone. Three disease intensity zones were designated from the maps (low, moderate, high) based on the density of SDS patches in an area. Disease incidence and severity, soil samples, surface firmness, thatch depth, and organic matter measurements were taken from 10 plots within each disease intensity zone from each of the four fairways (n = 120). Multivariate pairwise correlation analyses (P < 0.1) and best subset stepwise regression analyses were conducted to determine which edaphic factors most influenced the SDS epidemic within each fairway and each year. Edaphic factors that correlated with an increase in SDS or were selected for the best fitting model varied across holes and years. However, in certain cases, soil pH and thatch depth were predictors for an increase in SDS. No factors were consistently associated with SDS occurrence, but results from this foundational study of SDS epidemics can guide future research to relate edaphic factors to SDS disease development.

Biological Control of Weeds in turfgrass: opportunities and misconceptions.

Turfgrass systems may offer opportunities for overcoming some constraints on the successful implementation of weed biocontrol. Of the roughly 16.4 million ha of turfgrass in the USA, ≈60-75% are in residential lawns and 3% are golf turf. Annual expenditures for a standard herbicide treatment regimen for residential turf are estimated to be ≈US$326 ha-1 , about 2-3-fold greater than that for USA corn and soybean growers. Expenditures can be >US$3000 ha-1 for control of certain weeds such as Poa annua in high-value areas including golf fairways or greens, but those applications are made to far smaller areas. Regulatory actions and consumer preferences are creating market opportunities for alternatives to synthetic herbicides in both commercial and consumer markets, but the size of these markets and willingness-to-pay are poorly documented. Turfgrass sites are intensively managed, yet despite the ability to modify site conditions through irrigation, mowing and fertility management, microbial biocontrol agents tested thus far have not provided the consistently high levels of weed control expected in the market. Recent advances in microbial bioherbicide products may offer a path to overcome many of the obstacles to success. No single herbicide will control the diversity of turfgrass weeds, nor will any single biocontrol agent or biopesticide. Successful development of weed biocontrol for turfgrass systems will require numerous, effective biocontrol agents for the many weed species found in turfgrass environments, as well as a deeper understanding of different turfgrass market segments, and weed management expectations for each segment. © 2023 The Author. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Reduced Sensitivity to Fluopyram in Meloidogyne graminis following Long-Term Exposure in Golf Turf.

In recent years, some golf course superintendents in Florida have reported that the turf health is no longer as great, and nematode responses to fluopyram have decreased. The objective of this research was to determine if the mechanism of the reported reduced efficacy was attributable to either: i) enhanced degradation accelerating its breakdown in the soil, or ii) reduced sensitivity to the nematicide in the nematode populations. In a field experiment, soil and nematodes were collected from small plots that had been treated multiple times over four years, for only one year, or never treated. Soil and nematodes were additionally collected from commercial turf sites where either multiple applications of fluopyram had been made for numerous years, or it had never been used. Bioassay experiments found no evidence of enhanced degradation. However, M. graminis collected from small field plots and commercial sites with long-term use of fluopyram were less sensitive to fluopyram in-vitro than those from small plots and commercial sites where fluopyram had not been used. These results indicate that nematicide resistance is a likely cause of reduced fluopyram efficacy on golf-course turf in Florida.

Physiological and lipidomic response of exogenous choline chloride alleviating salt stress injury in Kentucky bluegrass (Poa pratensis).

Introduction: Choline participates in plant stress tolerance through glycine betaine (GB) and phospholipid metabolism. As a salt-sensitive turfgrass species, Kentucky bluegrass (Poa pratensis) is the main turfgrass species in cool-season areas. Methods: To improve salinity tolerance and investigate the effects of choline on the physiological and lipidomic responses of turfgrass plants under salinity stress conditions, exogenous choline chloride was applied to Kentucky bluegrass exposed to salt stress. Results: From physiological indicators, exogenous choline chloride could alleviate salt stress injury in Kentucky bluegrass. Lipid analysis showed that exogenous choline chloride under salt-stress conditions remodeled the content of phospholipids, glycolipids, and lysophospholipids. Monogalactosyl diacylglycerol, digalactosyl diacylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and lysophosphatidylcholine content were increased and phosphatidic acid content were decreased in plants after exogenous choline chloride under salt treatment. Plant leaf choline content increased, but GB was not detected in exogenous choline chloride treatment plants under nonstress or salt-stress conditions. Discussion: GB synthesis pathway related genes showed no clear change to choline chloride treatment, whereas cytidyldiphosphate-choline (CDP-choline) pathway genes were upregulated by choline chloride treatment. These results reveal that lipid remodeling through choline metabolism plays an important role in the salt tolerance mechanism of Kentucky bluegrass. Furthermore, the lipids selected in this study could serve as biomarkers for further improvement of salt-sensitive grass species.

The genetic variation in drought resistance in eighteen perennial ryegrass varieties and the underlying adaptation mechanisms.

BACKGROUND: Drought resistance is a complex characteristic closely related to the severity and duration of stress. Perennial ryegrass (Lolium perenne L.) has no distinct drought tolerance but often encounters drought stress seasonally. Although the response of perennial ryegrass to either extreme or moderate drought stress has been investigated, a comprehensive understanding of perennial ryegrass response to both conditions of drought stress is currently lacking. RESULTS: In this study, we investigated the genetic variation in drought resistance in 18 perennial ryegrass varieties under both extreme and moderate drought conditions. The performance of these varieties exhibited obvious diversity, and the survival of perennial ryegrass under severe stress was not equal to good growth under moderate drought stress. 'Sopin', with superior performance under both stress conditions, was the best-performing variety. Transcriptome, physiological, and molecular analyses revealed that 'Sopin' adapted to drought stress through multiple sophisticated mechanisms. Under stress conditions, starch and sugar metabolic enzymes were highly expressed, while CslA was expressed at low levels in 'Sopin', promoting starch degradation and soluble sugar accumulation. The expression and activity of superoxide dismutase were significantly higher in 'Sopin', while the activity of peroxidase was lower, allowing for 'Sopin' to maintain a better balance between maintaining ROS signal transduction and alleviating oxidative damage. Furthermore, drought stress-related transcriptional and posttranscriptional regulatory mechanisms, including the upregulation of transcription factors, kinases, and E3 ubiquitin ligases, facilitate abscisic acid and stress signal transduction. CONCLUSION: Our study provides insights into the resistance of perennial ryegrass to both extreme and moderate droughts and the underlying mechanisms by which perennial ryegrass adapts to drought conditions.

Use of a Dielectric Sensor for Salinity Determination on an Extensive Green Roof Substrate.

The irrigation of extensive green roofs with recycled or saline water could contribute to the conservation of valuable drinking water supplies. In such cases, the continuous monitoring of substrate electrical conductivity (ECsw) is of immense importance for the sustainable growth of the plants growing on the green roof. The present study aimed to estimate the ECsw (pore water EC) of an extensive green roof substrate in lysimeters with the use of the WET-2 dielectric sensor. Half of the 48 lysimeters that simulated extensive green roofs had a substrate depth of 7.5 cm, while the other half had a 15 cm substrate depth. The warm season turfgrass Paspalum vaginatum 'Platinum TE' was established at the lysimeters, and during the summer period, it was irrigated every two days at a rate of 14 mm with NaCl solutions of various electrical conductivities (ECi): (a) 3 dS m-1, (b) 6 dS m-1, and (c) 12 dS m-1, while potable water of 0.3 dS m-1 ECi served as the control. The relation between bulk electrical conductivity, σb, and bulk dielectric permittivity, εb, of the substrate was observed to be linear for all ECi levels up to σb values of 2-2.5 dS m-1. The ECsw was predicted by employing the salinity index method which was modified to be applied to the particular case of a green roof substrate. Knowing the salinity index and organic portion (%, v/v) for a given green roof substrate, we could calculate the ECsw. It was found that the use of the salinity index method predicts reliably the ECsw up to 10-11 dS m-1, while the method overestimates ECsw at very low levels of electrical conductivity.