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Kentucky bluegrass (Poa pratensis L.; drought resistant) and perennial ryegrass (Lolium perenne L.; drought sensitive) are economically important grass species contrasting in drought stress resistance. This study determined the optimal chlorophyll fluorescence parameters to indicate drought incidence and whether the parameters differentiate intra‐ and interspecies variations in drought stress. For each species, nine cultivars were exposed to well‐watered or drought (water withheld) conditions in growth chambers containing high‐throughput photosynthetic imagers to track real‐time responses of maximum quantum efficiency of photosystem II (Fv/Fm), quantum yield of photosystem II (ΦII), non‐photochemical quenching (NPQ), energy‐dependent quenching (qE), and photoinhibition‐associated quenching (qI). Soil moisture content and relative water content of leaf tissues were evaluated. Due to drought, Fv/Fm and ΦII decreased for cultivars of both species but earlier for perennial ryegrass compared to Kentucky bluegrass. The NPQ, qI, and qE values exhibited more dynamic and earlier changes due to drought compared to Fv/Fm and ΦII and allowed for early, mid, and late drought responses to be illustrated. Drought induced an increase in NPQ, qI, and qE values, which corresponded to activation of photoprotection mechanisms, and was exhibited earlier for perennial ryegrass compared to Kentucky bluegrass. As the drought treatment progressed, a decrease or stabilization of low values of NPQ, qI, and qE was observed, and the lowest values were associated with the most drought‐sensitive cultivars. These results indicate important stress tolerance protection mechanisms for grass species and will broadly impact basic and applied grass research as a nondestructive phenotyping tool. Core Ideas: Kentucky bluegrass and perennial ryegrass contrast in drought resistance.Chlorophyll fluorescence parameters during drought responses reveal novel insight into resistance mechanisms.Plant non‐photochemical protection strategies were activated by drought stress in both grass species.Measurements of non‐photochemical quenching parameters indicated drought responses earlier than quantum efficiency.Non‐photochemical parameters are good, early indicators of drought stress incidence in grass species. [ABSTRACT FROM AUTHOR]

Seed shattering is a key constraint to improvement of seed yield in perennial ryegrass and, as a result, seed retention is an essential trait for breeding of this valuable crop. It is unclear whether sources of seed retention are available to plant breeders. Field studies were conducted near Corvallis, OR in 2 yr (2017–2018 and 2018–2019) to identify genetic variation for seed retention and to ascertain whether there was variation for phenotypic traits that may contribute to seed loss due to shattering. The field studies examined the values and variation in these traits in 40 diverse global accessions and genotypic lines within accessions. Plant mortality was high as only 21 of the original 40 accessions survived in sufficient numbers for analysis. The accessions and genotypic lines exhibited great variation in growth habit, spikelets per spike, seeds per spike, seed weight, spike length, and seed retention. Seed retention among accessions ranged from 27.1 to 78.7% with a commercial cultivar at 42.4% retention. For the most part, the values and variation observed in other characteristics were similar to that found in perennial ryegrass in other investigations, and some materials were representative of commercial cultivars. This study presents evidence that sources of higher seed retention than is found in commercial cultivars of perennial ryegrass is available from these accessions and could be used in the breeding of shatter‐resistant cultivars. Core Ideas: Perennial ryegrass accessions with greater seed retention than commercial cultivars were identified. Physical traits were examined to determine the impacts on seed retention in perennial ryegrass. A phenotypic characterization method was established to evaluate seed retention more consistently. [ABSTRACT FROM AUTHOR]

During late spring and early summer, perennial ryegrass (Lolium perenne L.) produces reproductive structures (i.e., culm and inflorescence), that decrease turf quality due to stemminess (i.e., culm remaining) after mowing. Research is required to understand the impact of management practices on visible culm and inflorescence presence. Field experiments were conducted to evaluate perennial ryegrass culm, inflorescence, and turf canopy responses due to various nitrogen (N) fertilization levels, scalping timings and heights. In Experiment 1, N fertilization rates ≥24 kg N ha−1 applied in early May with a slow‐release fertilizer prior to peak flowering (i.e., late May to early June) visibly decreased culms and inflorescences compared with 0 and 12 kg N ha−1. Higher N fertilizer levels, especially 98 kg N ha−1, also resulted in fewer necrotic culms remaining later in the summer along with greater overall turf quality and reduced weed cover. In Experiment 2, scalping perennial ryegrass at 3.8 or 5.1 cm on 25 May, the closest proximity prior to peak flowering, provided the lowest area under the curve (AUC) of green flowering culms. Scalping during or after peak flowering resulted in similar AUC values compared with nonscalped (7.6 cm) turf but did decrease the presence of necrotic culms later in summer to help improve turf quality. Overall, N fertility with a slow‐release fertilizer or a well‐timed scalping influences spring culm and inflorescence density and necrotic culm stemminess in perennial ryegrass turf systems. Additional research on physiological responses, such as carbohydrate partitioning, to these management practices is required. Core Ideas: Spring N fertilization (≥24 kg N ha−1) decreases perennial ryegrass flowering culms.Scalping timing and height influence subsequent culm and inflorescence density.Necrotic culms in July and August were decreased by scalping in late May, June, or early July.A spring preemergence herbicide application should be included to reduce weed encroachment when scalping. [ABSTRACT FROM AUTHOR]

To extend golf play in early summer or hasten athletic field preparation in late summer, turf managers often desire to allow perennial ryegrass (Lolium perenne L.) to persist and compete with overseeded bermudagrass (Cynodon dactylon L. Pers.) or hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burtt Davy) during optimal growing conditions. Understanding how competition‐free growing degree‐days (CFGDD) influence bermudagrass total nonstructural carbohydrates (TNC), biomass, and visual green cover may aid in turf‐use scheduling. Twenty‐four weekly treatments of foramsulfuron eliminated perennial ryegrass competition in replicate plots and allowed assessment of competition‐free bermudagrass coverage, biomass, and TNC as related to cumulative heat and light units. Results from this study indicate that bermudagrass coverage is a function of cumulative CFGDD and competition‐free daily light integral (CFDLI) but is dependent on locations or years where cultivars or seasonal legacy are variable. At three locations, 'Patriot' and 'Midiron' hybrid bermudagrass and 'Riviera' bermudagrass required 603, 709, and 959 CFGDD and 2,447, 3,271, and 4,556 mol m–2 CFDLI to reach 97% coverage, respectively. Trends of TNC per unit area, however, continued to increase after full coverage was achieved and up to the point at which no more heat or light units were accumulated in fall. Absence of a clear asymptote in the trends suggests that heat or light units that were seasonally accumulated in Blacksburg, VA, were insufficient to achieve maximum bermudagrass carbohydrate reserves before winter dormancy. Core Ideas: Postdormancy bermudagrass coverage is a function of heat and light accumulation.Postdormancy bermudagrass aboveground biomass is a function of heat and light accumulation.Total nonstructural carbohydrates content per bermudagrass stolon was unaffected by perennial ryegrass competition. [ABSTRACT FROM AUTHOR]

The effect of soil environment on cultivars compatibility was evaluated in a cutting field experiment during two growing seasons. A factorial combination of four perennial ryegrass (Lolium perenne L.; PR) and three white clover (Trifolium repens L.; WC) cultivars were grown on deep (DSS) and shallow (SSS) soils under irrigated conditions. Measurements included herbage accumulation (HA), root attributes, leaf chlorophyll content, and interception of photosynthetic radiation. The PR–WC compatibility was affected by soil environment. In both soil sites and growing seasons, the WC + PR herbage accumulations were similar but with different PR and WC partial accumulation. In DSS, the partial PR HA was 22% less than that observed in SSS; the partial WC HA was almost twice in DSS relative to SSS. In SSS, the WC stolon growing point numbers, stolon length, and stolon biomass increased 60, 88, and 94% relative to DSS, respectively. In the same way, the mixed sward increased root biomass and root length density, which was considered as a mechanism for improving plant resources capture from the soil. At cultivar level, the PR–WC compatibility was affected mainly by WC cultivar, and the effect of PR cultivar was fairly weak. The medium‐leaved WC cultivar 'Will' showed the greatest compatibility with PR, particularly with cultivar 'Bealey'. These results are valuable when designing new management strategies for mixed sward production in marginal environments. Modern cultivars of PR have capacity for adapting to marginal environments; however, it is necessary to improve the competitive ability of WC to capture soil resources under marginal soil conditions. Core Ideas: Understanding compatibility of perennial ryegrass and white clover cultivars allows for optimized mixed sward herbage accumulation.Modern cultivars of perennial ryegrass have capacity for adapting to marginal environments.Mixed sward changes its phenotypic expression in marginal environments. [ABSTRACT FROM AUTHOR]

Bleaching of young leaf tissue is a common response to the herbicide mesotrione and varies from one application to another. To better elucidate factors that may contribute to perennial ryegrass (Lolium perenne L.) phytotoxicity from mesotrione, studies were conducted at Blacksburg, VA. Continuous field monitoring of temperature, humidity, solar radiation, soil moisture, and leaf wetness was used to elucidate environmental conditions that led to perennial ryegrass injury by mesotrione applied at 0.14 kg a.i. ha−1. The study found that 2 of 17 weekly treatments caused unacceptable perennial ryegrass injury at two field sites. Ten‐day temporal trends prior to mesotrione treatment showed that temperature, for one injury event, and volumetric soil water content, for the other injury event, were exclusively correlated to visually and digitally assessed perennial ryegrass injury. Both instances suggest that alleviation of suboptimal temperature or moisture with more optimal growing conditions influenced the turf injury response. Additional studies in growth chambers showed that carotenoid levels and turf phytotoxicity were strongly temperature dependent and followed a quadratic response with peak injury occurring at perennial ryegrass growth optima. Carotenoid levels decreased and perennial ryegrass injury increased in response to increased mesotrione rate. These data suggest that mesotrione is more likely to injure perennial ryegrass turf when used at higher rates and under conditions of rapid turfgrass growth. [ABSTRACT FROM AUTHOR]

Turf‐type perennial ryegrass (Lolium perenne L.) success depends on adequate turfgrass quality and economical seed yield. In most breeding programs, spaced plants are the initial unit of selection in which observations of related individuals dictate the selection of superior germplasm for further testing. Therefore, spaced plants must be predictive of seed production and turfgrass growing environments. This study investigated the effectiveness of standard (three plants m−2) and competitive (23 plants m−2) spaced‐plant nurseries as selection environments with respect to two sward environments as well as applying a novel image analysis technique for several key traits. Seed production, turfgrass, and the two spaced‐plant growing environments were tested at two locations in Minnesota. Turfgrass quality traits were measured in 2017 and 2018 and seed production traits were measured in 2018. Automated image analysis was able to predict the traditional visual scoring values at both locations for crown rust (Puccinia coronata f.sp. lolii) severity [Pearson's correlation (rp) > 0.79, P <.001], winter injury (rp > 0.89, P <.001), and turfgrass texture (rp > 0.88, P <.001). Increasing the competition among spaced plants altered the plant phenotype and improved accuracy for vegetative biomass, crown rust severity, seed yield, and, at one location, turfgrass quality. There was no benefit of increasing competition for several traits such as genetic color, fertile tillers, and spikelet number. Although the competitive design was not useful for all traits, pragmatically, the competitive design used less space and often made measurements and observations easier for bunch‐type grasses. [ABSTRACT FROM AUTHOR]

Cool‐season turfgrasses can be subjected to salt stress through a variety of sources, and selection for salt tolerance is an increasingly high priority. Two of the main turfgrass species in temperate regions are perennial ryegrass (Lolium perenne L.) (PRG) and Kentucky bluegrass (Poa pratensis L.) (KBG), and greenhouse evaluations have occurred to rank and characterize salt tolerance in each species. However, salt tolerance in a field setting in a semiarid climate has not been tested, and the genetic mechanisms by which each species specifically responds to salt stress is still unclear. In this study, we evaluated salt tolerance of 10 PRG and 12 KBG entries in a field setting and compare their salt tolerances to two alkaligrass cultivars. Using electrolyte leakage (EL) and turf green cover, tolerant and susceptible cultivars and accessions were identified from both species. Transcriptome‐level gene expression analysis was applied on a subset of the entries, and 62 differentially expressed transcripts were shared among the three species with a preponderance of transcripts involving carbohydrate metabolism, oxidation‐reduction processes, and ion transport within the cell. Upon further gene enrichment analysis of KBG, more transcripts in those three categories were found. The differentially expressed transcripts (DETs) represent mechanisms by which PRG and KBG respond to salt stress, as well as targets for selection for salt tolerance. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) is an important turf and forage species that often becomes infected with Puccinia coronata f. sp. lolii, the causal pathogen of crown rust. Disease control through clavicipitaceous endophytes has been proposed as a potential biocontrol. Two field experiments were designed to determine the influence of native Epichloë endophyte infection on natural rust development across a diverse panel of perennial ryegrass germplasm. Experiment 1 used an isogenic population design in which infected (E+) or endophyte‐free (E−) clonal plants were nested within 14 perennial ryegrass entries. Experiment 2 consisted of isofrequent E+ and E− progeny from isogenic parents. Results showed the endophyte had no consistent main effect on crown rust severity among or within entries; however, several isogenic host pairs did show either favorable or antagonistic effects. Despite these sporadic effects, no differences were found between isofrequent family pairs, indicating the presence of a host × endophyte interaction. Genotypic and phenotypic data revealed that endophyte isolates were similar within entry, indicating that host genotype could be responsible for the highly specific endophyte effect on crown rust. The preponderance of host resistance in mediating rust severity was supported by large broad (>.75) and narrow‐sense (.76) heritability estimates. These findings support the conclusion that endophyte infection does not play a substantial role in mediating crown rust severity on a population scale in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Forage production in the southeastern United States relies heavily on cool‐season grasses in winter and spring. The most prolific species is annual ryegrass (Lolium multiflorum Lam.), a winter annual. Historically, secondary seed dormancy of ryegrass inhibits germination at soil temperatures in excess of 21°C. Normal planting occurs in early‐mid fall (mid‐October). However, earlier planting (Aug. or Sept.) could expand the grazing period. This work sought use of recurrent phenotypic selection (RPS) to breed an annual ryegrass cultivar that could germinate at high temperatures and survive high temperatures post‐germination. All selections were conducted in a growth chamber at 40:30°C (12:12 h, light/darkness). Germinated seedlings were subjected to 2–3 wk of 40:30°C conditions post‐germination. Selected individuals (Cycle 1) and the base germplasm (Cycle 0) were transplanted to the field in fall 2015, and harvested for seed in spring 2016. Germination tests were conducted to compare mean cumulative germination, velocity of germination within 8 d (VOG8), and realized heritability (h2) at 40:30°C. Selection was repeated twice to reach Cycle 3. Data from the 2018 germination tests indicated that germination of Cycle 3 seed (45.8%) was significantly greater (P <.001) within 14 d than that of all previous cycles. Cycle 3 VOG8 was 8 times that of Cycle 0. Total additive gene action was estimated by a calculated realized heritability of h2 =.41. These data indicate improved germination under high temperatures was achieved in nearly half the population. This will potentially allow for late‐summer planting and greater grazing time. [ABSTRACT FROM AUTHOR]

Bahiagrass (Paspalum notatum Flüggé) is the base of cow‐calf operations in Florida. Nitrogen is usually the most limiting mineral in pasture‐based systems. Various bahiagrass cultivars have been released over the years; however, an evaluation of their performance under no N fertilization has not been reported. There is some evidence that bahiagrass can associate with free‐living bacteria and fix atmospheric N2. This study investigated the performance and potential biological N2 fixation (BNF) of six bahiagrass cultivars ('Argentine', 'AU Sand Mountain', 'Pensacola', 'TifQuik', 'Tifton‐9', and 'UF‐Riata') under no N fertilization during the growing seasons of 2014, 2015, and 2016. Results showed no differences among cultivars for total herbage accumulation (2835 kg dry matter ha−1), total N aboveground (28 kg N ha−1 yr−1), and BNF (9 kg N ha−1 yr−1). Pensacola had greater crude protein than Tifton‐9 (84 vs. 78 g kg−1, respectively), whereas AU Sand Mountain had greater in vitro digestible organic matter (494 g kg−1) than other cultivars, except for Argentine. Argentine had greater root‐rhizome mass (24,914 kg organic matter ha−1) than UF‐Riata and TifQuik (15,367 and 14,682 kg organic matter ha−1, respectively). Carbon and N stocks in belowground biomass were greater in Argentine (8575 and 155 kg ha−1, respectively) than UF‐Riata (4514 and 85 kg ha−1, respectively). Root‐rhizome/shoot ratio averaged 37 across cultivars. Managing bahiagrass cultivars under no N fertilization inhibits the cultivar herbage potential; however, cultivar differences in nutritive value and root‐rhizome responses can still be detected. [ABSTRACT FROM AUTHOR]

Characterizing phenotypes in germplasm collections and making data publicly available is crucial to ensure the utilization of the accessions in breeding programs. Variance component estimates are used to calculate genetic parameters needed to make strategic decisions for germplasm conservation and its utilization in plant breeding. This information is lacking for annual ryegrass (Lolium multiflorum Lamarck) germplasm from the USDA National Plant Germplasm System (NPGS). In this study, we estimated variance components, repeatability, genotypic values, genetic correlations, and genotype × year correlations for 18 traits in 167 annual ryegrass populations. Repeatability (H2) ranged from 0.11 to 0.93 for single‐year analyses, and from 0.03 to 0.86 for traits evaluated during two growing seasons, evidencing the presence of genetic variability. Genotype × year correlations ranged from 0.17 up to 0.99, demonstrating variable consistency in phenotypic performance across years. Combining multiple traits in one cultivar is a challenge for breeders, particularly for traits negatively correlated. Establishment, plant vigor, leaf width and length, and chlorophyll content were negatively correlated with disease traits. Heading date was positively correlated with number of tillers, crown size, and biomass production. High positive correlations were also found between biomass and plant height, crown size, tiller number and size, and leaf/stem ratio. The data presented in this study will become publicly available via the Germplasm Resource Information Network (GRIN)‐Global database of the NPGS. [ABSTRACT FROM AUTHOR]

Festulolium is the result of hybridization between Lolium and Festuca species. Amphidiploid festulolium produced by crosses between tetraploid Lolium species (L. multiflorum Lam. and L. perenne L.) and Festuca pratensis (F. pratensis Huds.) exhibits genome balance drift, thereby favoring Lolium over numerous generations. In a previous report, we found no decrease in the f ratio (the ratio of total area of Festuca‐specific genome regions to the total area of all genome regions) in maternally derived progeny over generations, suggesting that seed yield can cause Lolium‐favored genome balance drift. In this study, we investigated seed yield, ripening rate, germination rate, and seed weight in the field for 2 yr in festulolium plants with f ratio over and under 50%. The over 50 f ratio group had significantly lower seed yields, ripening rates, and germination rates than the under 50 f ratio group. Further correlations between seed yield‐related traits and f ratio values revealed that germination rate was negatively correlated with f ratio in the over 50 f ratio group. Simulated next‐generation f ratios were 2% lower than the actual f ratio values of maternal plants. Our study shows that Lolium‐favored genome balance drift can solely be caused by phenotypic differences, regardless of any biases toward Lolium occurring during meiosis. [ABSTRACT FROM AUTHOR]

Nitrogen fertilization is a major input cost of forage production, and alternatives that maintain yield and nutritive value would be advantageous. A 3‐yr study was conducted to evaluate forage nutritive value and clover proportion when N fertilizer was replaced partially with interseeded clovers (Trifolium spp.) or protein supplements for stocker cattle grazing annual ryegrass (Lolium multiflorum Lam.). Nitrogen delivery methods with or without monensin included annual ryegrass fertilized with 112 kg N ha−1 in split application (NFERT), and other methods that received 56 kg N ha−1, including annual ryegrass interseeded with crimson clover (CC, Trifolium incarnatum L.) or arrowleaf clover (AC, Trifolium vesiculosum Savi), or grazing cattle supplemented with distillers dried grains plus solubles at a rate of 0.65% body weight daily (DDGS) or whole cottonseed (Gossypium hirsutum L.) at the rate of 0.65% body weight daily (WCS). Clover proportion was greater (P = 0.003) for CC than AC across all 3 yr of the study, and CC was more (P = 0.003) abundant when monensin was fed. Year affected forage in vitro true digestibility (IVTD, P < 0.001) and crude protein (CP, P < 0.001) concentration such that IVTD and CP were greatest in Year 3, intermediate in Year 2, and least in Year 1. Forage degradable intake protein (DIP) concentration was affected by N delivery method (P < 0.001) and year (P < 0.001) such that CC was less than NFERT, DDGS, WCS, and AC, and Year 1 was greatest, Year 2 was intermediate, and Year 3 was the least. Results are interpreted to mean that year affected forage nutritive value more than did N delivery method. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a unique new plant breeding decision support software tool DeltaGen, implemented in R and its package Shiny. DeltaGen provides plant breeders with a single integrated solution for experimental design generation, data quality control, statistical and quantitative genetic analyses, breeding strategy evaluation, simulation, and cost analysis, pattern analysis, index selection, and underlying basic theory on quantitative genetics. Key analysis procedures in DeltaGen were demonstrated using three datasets generated from forage breeding trials in Australia, New Zealand, and the United States. Analyses of the perennial ryegrass seasonal growth data in Case Study 1 was based on residual maximum likelihood analysis and pattern analysis. A graphical summary of the performance of entries across locations was generated, and entries with specific and broad adaptation were identified. The quantitative genetic analysis and breeding method simulation procedures applied to the perennial ryegrass half-sib (HS) family data in Case Study 2 enabled estimation of quantitative genetic parameters, prediction of genetic gain, and calculation of costs per selection cycle. These results enabled comparison of three breeding methods, which also included genomic selection, and their simulation. Data from Case Study 3 were analyzed to investigate a multivariate approach to identify HS families of switchgrass with breeding values that would enable an increase in biomass dry matter yield (DMY) and cell wall ethanol (CWE) and a decrease in Klason lignin (KL). The Smith- Hazel index developed enabled identification of HS families with genetic worth for increasing DMY and CWE and reducing KL, in contrast with individual trait selection. Analysis of the datasets in all three case studies provides a snapshot of the key analyses available within DeltaGen. This software tool could also be used as a teaching resource in plant breeding courses. [ABSTRACT FROM AUTHOR]

The quest to reduce importation of plant protein for livestock feed and to reduce expense and environmental consequences of nitrogen fertilizer use have resulted in renewed interest in forage legumes in EU countries. The objectives of this study were: (i) to assess forage accumulation and nutritive value of mixtures of Italian ryegrass (IRG, Lolium multiflorum Lam.) and kura clover (KC, Trifolium ambiguum M. Bieb.), and (ii) to model milk production potential of this mixture, relative to IRG and KC monocultures in northern Poland. Italian ryegrass and KC were grown in monocultures or intercropped (IRGKC mixture) and harvested three times per year in two consecutive years. Italian ryegrass had greatest accumulated forage in harvest 1 and 2, followed by IRG-KC and the KC monoculture. In harvest 3, IRG-KC accumulated more forage than KC or IRG. Crude protein, neutral detergent fiber digestibility, and in vitro true digestibility across harvests followed the trend KC > IRGKC > IRG. The KC monoculture had the greatest calculated milk per megagram dry matter but the least milk per hectare, whereas IRG monoculture had least milk per megagram dry matter and greatest milk per hectare, with intermediate values for the IRG-KC mix. Although forage accumulation of the mixture was less than that of nitrogen fertilized IRG, greater crude protein concentration and no nitrogen fertilizer application make it an intriguing opportunity for EU countries striving to reduce feed protein imports and use of fertilizer nitrogen. [ABSTRACT FROM AUTHOR]

The article presents a study on alternative management options for multiyear perennial ryegrass seed production in Northern Minnesota. Topics include the use of plant growth regulators (PGRs) and fall residue management, such as open burning, baling, and mowing, to achieve multiyear seed production in northern climates.

Poor winter hardiness is one of the factors limiting the use of the palatable and productive coolseason forage grass perennial ryegrass (Lolium perenne L) in the northeastern United States. We compared freeze tolerance among seedlings of 13 commercial cultivars of perennial ryegrass in a controlled environment chamber. After a 14-d acclimation period, plants were chilled to -10, -15, or -20°C for 1 h, then gradually warmed. After 36 d, surviving plants were counted then harvested and weighed. Mortality rate varied significantly among cultivars (0-13% at -10°C, 47-100% at -20°C). The temperature at which 50% of plants would die (LT50) ranged from -12.9 to -20.8°C. Hardiness ratings provided by the breeder did not match well with LT50 except for the most hardy cultivars. Extreme minimum temperature predictions were extracted from regional climate forecasts for three 30-yr periods: baseline (1960-1989), short-term future (2015-2044), and long-term future (2070-2099). During the baseline period, only 2 to 33% of the northeastern United States was warm enough for these cultivars to survive during at least 50% of winters. Potential tolerable area may increase to 57 to 88% by 2099. Although other factors such as snow cover and variability of winter temperatures affect winter survival in the field, breeding for freeze tolerance has increased the potential extent of perennial ryegrass. Further improvements and the changing climate may greatly increase the utility of perennial ryegrass as a forage in the northeastern United States. [ABSTRACT FROM AUTHOR]

Freezing tolerance in perennial ryegrass (Lolium perenne L.) can be dramatically increased by a period of cold acclimation. To understand the mechanisms of cold acclimation and freezing tolerance in L. perenne, a crossspecies microarray study was conducted by using total RNA from cold-acclimated and nonacclimated L. perenne to hybridize with Affymetrix Barley1 GeneChips from barley (Hordeum vulgare L.). Our results indicate that selection of proper background correction and normalization method is critical for the success of a barley-perennial ryegrass crossspecies microarray study. By using a specific three-step normalization method, a total of 2870 (12.6%) genes out of approximately 22,000 genes on the barley gene chip were identified as differentially regulated by either 1 or 7 d of cold acclimation. Quantitative reverse transcriptase polymerase chain reaction (qRTPCR) analysis confirmed that the expression patterns of 14 selected genes are consistent with the signal intensity patterns observed in the microarray study, supporting the validity of using a cross-species microarray in studying gene expression in species for which genomic resources remain scarce. Gene ontology analysis of differentially regulated genes indicates that different biological processes, cellular components, and molecular functions responded differently to cold acclimation in observable temporal patterns, suggesting that perennial ryegrass gradually acquires freezing tolerance by systematically regulating gene expression in an orderly manner. [ABSTRACT FROM AUTHOR]

Breeding of perennial ryegrass (Lolium perenne L.) for forage is mainly aimed at increase in herbage yield. However, abiotic stresses such as drought and winterkill threaten persistence and ability to produce stable aerial biomass of the plant. Field experiments, performed under natural conditions, rather than dissection of abiotic stress factors under artificial or semiartificial conditions, offers opportunity to evaluate the effect of complex of abiotic stresses on the plant performance. The aim of this study was to evaluate the relationship between dry matter yield and tolerance to winter kill and drought of perennial ryegrass ecotypes and cultivars differing in their ploidy level during a 2-yr period. The field experiment was located in Akademija, Lithuania (55°40' N, 23°87' E) in 2015 and 2016. The germplasm consisted of 128 diploid and 25 tetraploid perennial ryegrass populations. Winterkill, spring growth and regrowth after cuts, drought damage, and dry matter yield were assessed. Short periods of lower than -10°C temperatures with slim snow cover determined low damages of the perennial ryegrass after winters. Medium correlation was estimated between drought damages and dry matter yield. Tetraploid genotypes of perennial ryegrass demonstrated higher tolerance to cold and drought stress conditions, better spring growth and regrowth after cuts, and higher dry matter yield. [ABSTRACT FROM AUTHOR]

Genomic selection (GS) has been recognized as offering numerous potential benefits for ryegrass (Lolium perenne L.) breeding. While the theoretical benefits of GS in ryegrass breeding are clear, the best way to apply GS in practical breeding programs remains to be determined. The present study aimed to investigate genomic breeding options that best balance genetic gain, breeding costs, and the level of inbreeding using stochastic simulation. Nine GS scenarios were tested, including different numbers of selection candidates (10,000, 5000, and 2000 F1 seedlings) and three reference population sizes for GS composed of plots representing a sward-based trial (500, 200, and 100 plots). Low to moderate prediction accuracy was achieved for productivity traits across cycles (i.e., 0.1–0.45 for yield [h2 = 0.3]). Scenarios with larger reference populations (i.e., 500 plots) achieved higher prediction accuracy but, when considering field trial costs, were more expensive per unit of genetic gain. All nine GS scenarios delivered significantly higher genetic gain (up to fourfold) than the conventional breeding scenario over a 20-yr period. Scenarios with moderate selection intensity on F1 seedlings with fewer plots tested in field gave the most genetic gain per dollar invested (i.e., 2000 or 5000 F1 seedlings and 100 plots). However, all GS scenarios reduced genetic diversity in the breeding population more than phenotypic selection, highlighting the need to mitigate inbreeding when applying GS in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Cool-season forage mixtures are an option for extending the length of the grazing season. Small grains have a different growth distribution than annual ryegrass and may increase livestock gain per area. This 2-yr grazing study tested three small grain-annual ryegrass mixtures: (i) cereal rye (Secale cereale L. 'FL401')--annual ryegrass (Lolium multiflorum Lam. 'Prine'); (ii) oat (Avena sativa L. 'Horizon 201')--annual ryegrass Prine; (iii) triticale (xThticosecale spp. Tri-cal 342')-annual ryegrass Prine. Stocking rate was adjusted, based on herbage allowance, using continuous stocking. Response variables included herbage mass, herbage allowance, herbage accumulation rate, herbage N, herbage in vitro organic matter digestibility (IVOMD), botanical composition, average daily gain (ADG), grazing days, stocking rate (SR), gain per area, and blood urea N (BUN). Seasonal and annual variation occurred for most of the responses, but total season animal production was similar among mixtures. The ADG in 2014 was 0.90 and 0.85 kg head-1 d-1 in 2015. Stocking rate varied among mixtures within sampling dates and years, but season-long average SR was similar among mixtures. Total season animal gain was 367 kg body weight (BW) ha-1 in 2014 and 313 kg BW ha-1 in 2015. Small-grain species and varieties resulted in different growing curves, with FL401 cereal rye being the earliest variety in the present study. Oat and triticale demonstrated a more evenly distributed growth rate along the season, facilitating the adjustment of the stocking rate and grazing management. [ABSTRACT FROM AUTHOR]

Currently, the standard germination test (SGT) is the official test for evaluating seed viability in seed testing laboratories around the world. The SGT takes 3 to 4 wk to complete for most grasses, including the dormancy breaking treatment period. The tetrazolium test (TZT), however, offers quick viability determination within 24 to 48 h, even for dormant seeds. This study was conducted to compare SGT and TZT results for tall fescue (TF), annual and perennial ryegrass (ARG and PRG), orchardgrass (OG), bentgrass (BG), Kentucky bluegrass (KBG), and fine fescues (FF). A total of 3432 samples representing the seven species were evaluated for viability by SGT and TZT during 2009 to 2013 at the Oregon State University Seed Laboratory (OSUSL). According to the germination tolerance table of the Association of Official Seed Analysts (AOSA), both SGT and TZT results were within tolerance in 94.2% of TF samples, 95.2% of ARG samples, 90.4% of PRG samples, 93.7% of OG samples, 90.8% of FF samples, 83.9% of BG samples, and 42.4% of KBG samples. Dormancy was the main reason for higher viability by TZT results than by SGT in the same sample, causing the two test results to be out-of-tolerance. Based on these results, it can be concluded that the TZT can be used as an alternative viability test to the SGT for TF, ARG, PRG, OG, FF, and possibly for BG. However, the KBG has higher levels of dormancy, which brings the SGT below the TZT results, especially for freshly harvested seeds. [ABSTRACT FROM AUTHOR]

Seeding rates (SRs) and row-spacing widths (RSWs) in perennial ryegrass (Lolium perenne L.) seed production are variable and the impacts of these factors on perennial ryegrass seed yield and plant growth characteristics are not well characterized. Experiments were conducted during 2010 and 2011 in first-year seed production fields near Roseau and Roosevelt, MN, where five SRs (1.3, 2.6, 5.2, 7.8, and 10.4 kg pure live seed [PLS] ha−1), three RSWs (10, 20, and 30 cm), and three N rates (67, 112, and 157 kg N ha−1) were evaluated in a split-split plot design under nonirrigated conditions. The 30-cm RSW resulted in 45% greater stem rust incidence, 8% fewer fertile tillers, and up to 2% greater 1000-seed weight (TSW) vs. the 10-cm RSW. For every unit of N applied, N increased biomass by 4 to 25 kg ha−1, fertile tillers by 3.7 tillers m−2, and seed yield by up to 4.7 kg seed ha−1, depending on environment. The 7.8 and 10.4 kg PLS ha−1 SRs combined with the 10-cm RSW, 157 ha−1 N rate, and other management factors, nearly eliminated weeds (<2% weed cover) compared with with wider RSWs and lower SRs. Weed cover was always inversely correlated with early-season vegetative cover (EVC). Seeding rates of 2.6 kg PLS ha−1 and greater resulted in similar seed yields suggesting that early-season plant density is not as important for seed yield as other management factors such as N rate, which significantly improved seed yield in three environments.

Glyphosate effectively controls susceptible biotypes of numerous weed species, but applications are often injurious to turfgrass. 'Aurora Gold' hard fescue (Festuca longifolia Thuill.) and 'JS-501' perennial ryegrass (Lolium perenne L.) have enhanced tolerance to glyphosate compared with traditional varieties, but the mechanisms that convey tolerance are not well understood. The objectives of this research were to investigate the physiological basis for glyphosate tolerance in Aurora Gold hard fescue and JS-501 perennial ryegrass. In greenhouse experiments, the estimated glyphosate rate required to reduce dry shoot mass 50% from the nontreated shoots at 4 wk after treatment measured >3360, >3360, 1850, and 1310 g acid equivalent (a.e.) ha-1 for Aurora Gold, JS-501, 'Manhattan V' perennial ryegrass, and 'Stonehenge' hard fescue, respectively. Absorption of 14C-glyphosate was similar between hard fescue cultivars and averaged 5% of the applied radioactivity. However, Aurora Gold accumulated 20% less shikimate than Stonehenge when incubated at ≥250 μM of glyphosate in leaf disk assays. JS-501 perennial ryegrass absorbed less 14C-glyphosate than Manhattan V (13 vs. 22% of the applied) and accumulated ~50% less shikimate. All cultivars translocated the majority of absorbed radioactivity out of the treated leaf. Based on these findings, glyphosate has less target-site inhibition in Aurora Gold compared with a more susceptible hard fescue cultivar. The glyphosate tolerance of JS-501 perennial ryegrass involves two mechanisms including less absorption and target-site inhibition from a more susceptible cultivar. [ABSTRACT FROM AUTHOR]

An increasing amount of reclaimed water is being used in turfgrass management; however, reclaimed water is often high in total dissolved salts and can result in salt stress injury and poor turf quality. The objectives of this study were to (i) determine the broad-sense heritability estimate of salinity tolerance of 142 perennial ryegrass (Lolium perenne L.) genotypes and (ii) determine narrow-sense heritability estimates and evaluate inheritance characteristics of salinity tolerance (heterosis, maternal effects, and combining ability) of progeny from crosses between fixed resistant and susceptible clones. Six replicates of each clone were irrigated overhead with a salt solution and were rated visually for percentage green color. The broad-sense heritability estimate for salinity tolerance was 0.78, indicating that the majority of the phenotypic variation was due to genetic effects. A diallel cross between three salt-tolerant and three salt-sensitive parents was performed in 2006. Parents and progeny were established, irrigated overhead with a salt solution, and visually rated for percentage green in 2007 and 2008. Narrow- sense heritability ranged from 0.72 (2007) to 0.66 (2008), indicating that the majority of the phenotypic variation was due to additive gene effects. No heterosis or maternal effects were found and general combining ability (GCA) accounted for more variance than specific combining ability (SCA). These results support the finding that salinity tolerance in perennial ryegrass is strongly controlled by additive gene effects. These data support a recurrent selection program that concentrates additive alleles as an effective breeding strategy to improve salinity tolerance in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Implementation of genomic selection (GS) for the genetic improvement of forage crops, such as perennial ryegrass, requires the establishment of sufficiently large training populations with high-quality phenotype and genotype data. This paper presents estimates of genetic and environmental variance and covariance components, obtained in a training population of 1453 F2 families. These families were produced in 2001, 2003, 2005, and 2007, and they were tested at seven locations throughout Europe. Families were cultivated together with commercial varieties that were used as control. Analyses focused on forage yield (green and dry matter) and six traits scored by visual inspection (i.e., rust resistance, aftermath heading, spring growth, density, winter hardiness, and heading date). Data were analyzed with linear mixed models, including fixed effects (trial and control varieties, within year and location), and random effects (breeding values, pedigree or parents, repeated effects of family or parents within location, and within trial environmental effects, to recover interblock information). Results showed very significant genetic variances for all traits, which provide good opportunities for future GS-based breeding programs. Forage yield showed family heritabilities of up to 0.30 across locations and up to 0.60 within a location. Similar or moderately lower values were found for the other traits. In particular, the heritabilities of rust resistance and aftermath heading were very promising. Genetic correlations between traits were generally low but positive, which increases the potential for multitrait selection. [ABSTRACT FROM AUTHOR]

Spatially separated pastures may reduce foraging costs and provide a better balance of nutrients. The objective was to evaluate the grazing behavior of stocker heifers grazing different spatially arranged pastures. Treatments (three replicates) were: (i) annual ryegrass (Lolium multiflorum Lam.; RG); (ii) mixed (MIX) sward of annual ryegrass and clover mix (berseem [Trifolium alexandrinum L.], white [T. repens L.], and red clover [T. pratense L.]); (iii) clover mix (CL) alone; and (iv) adjacent areas (ADJ) of annual ryegrass and clover mix. Crossbred beef heifers (n = 48; 224 ± 14 kg) were continuously stocked at 2.5 heifers ha-1. Visual and video recording observations and pedometers were used to study grazing behavior. Forage mass and nutritive value and body weight of heifers were determined every 15 d. Crude protein content of CL and ADJ was greater (P = 0.02) than RG. Concentration of water-soluble carbohydrate (WSC) was greater in RG than on CL. Heifers spent more time (P < 0.05) walking on RG and MIX when compared to those on ADJ. Grazing time was greater for heifers on RG compared to CL. Annual ryegrass had a greater concentration of WSC in the afternoon (221 g kg-1 DM) than in the morning hours (129 g kg-1 DM) and was greater than the concentration in the CL (99 and 61 g kg-1 DM, respectively). The concentration of WSC may explain the increase in grazing preference of RG during the afternoon; however, the reduction in the proportion of berseem clover during the last 30 d may have affected heifers' grazing behavior. [ABSTRACT FROM AUTHOR]

Determination of animal preference in the early stages of the evaluation process of new forages may provide insights into potential animal performance as well as plant responses to grazing. A 2-yr study was conducted at Raymond, MS, to determine grazing preference of cattle between tetraploid and diploid annual ryegrass (Lolium multiflorum Lam.) cultivars and its relationship with morphological and chemical characteristics. Treatments were two tetraploid cultivars, Maximus and Nelson, and two diploid cultivars, Marshall and Gulf, arranged in a 4 × 4 Latin square design experiment. Eight Angus crossbred yearling steers (Bos taurus) (initial body weight of 320 ± 19 kg) were used to determine grazing preference based on herbage disappearance, the Chesson-Manly (CM) index, and amount of time spent grazing. In both years, herbage disappearance was greater for the tetraploid (1380 kg ha-1) than diploid cultivars (895 kg ha-1), with greater CM index for the tetraploid than for the diploid cultivars (8.1 vs. 5.8% in Year 1 and 6.9 vs. 5.5% in Year 2). Also, animals spent about 10% greater time grazing the tetraploid than diploid cultivars during both years. During the first year, the tetraploid cultivars had less neutral detergent fiber (NDF) (556 vs. 589 g kg-1) and less acid detergent fiber (ADF) (341 vs. 359 vs. g kg-1) than the diploid cultivars and Nelson had greater watersoluble carbohydrate (WSC) concentration (184 g kg-1) than the other three cultivars (152 g kg-1). In the second year, NDF, ADF, and WSC were not different among cultivars. Tetraploid cultivars had a greater proportion of leaf than diploid cultivars. The results indicate that cattle showed greater preference for tetraploid cultivars, which appeared to be linked mainly with pregraze herbage mass and the proportion of leaf. [ABSTRACT FROM AUTHOR]

Broadening the genetic pool of crop species by wide hybridization is an established practice in plant breeding. Festuca × Lolium hybrids (Festulolium [FL]) are already established as commercial forage grasses around the world. By recurrent selection for drought and heat tolerance we developed turf-type populations of FL with increased stress tolerance. This improvement appeared associated with the presence of an introgression of meadow fescue [Festuca pratensis (Huds.) P. Beauv.] chromatin on chromosome 3 of perennial ryegrass (Lolium perenne L.). To determine if deeper and more extensive root characteristics were responsible for increased stress tolerance, a greenhouse study was conducted on FL both with and without the introgression, parental controls, and tall fescue (F. arundinacea Schreb.). In two experiments in sand-filled tubes, meadow fescue (MF) produced the deepest roots, most root biomass, and highest root:shoot ratio; FL and perennial ryegrass (PR) were intermediate while tall fescue (TF) ranked at or near the bottom for these traits. The results suggested that drought tolerance in FL was not a consequence of altered root depth or biomass. In a 2-yr field study of drought tolerance at deficit irrigation (50-70% ET0), turf quality of FL and PR was significantly greater compared to the fescues; FL populations appeared to offer greater turf quality during drought conditions than the fescues, but they did not differ from PR itself. In only 1 yr were mature TF stands equal to PR and FL in recovery rates. While the actual mechanism is still obscure, it appears that, with additional breeding and selection, FL hybrids have the potential to withstand water deficit at least as well as TF, while providing better turf quality. [ABSTRACT FROM AUTHOR]

One of the most accepted and adopted measures to assure coexistence of genetically modified (GM) maize (Zea mays L.) and conventional or organic maize is an isolation distance between GM and non-GM fields. If crop types used as "gap crops" differ in their effect on pollen- mediated gene flow this might have implications for the development of coexistence measures. Therefore, in a 3-yr study, the effect of a 25 m wide strip of barley (Hordeum vulgare L.) stubble and clover-grass (Trifolium pratense L. and Lolium spp.) as a gap crop on pollen-mediated gene flow in maize was investigated at two sites in northern Germany. It was hypothesized that different thermal conditions above the dry (barley stubble) and the wet (clover-grass) gap crop may cause differences in pollen-mediated gene flow into the adjacent recipient fields. Due to a ban on GM-maize cultivation in Germany, kernel color was used as a phenotypic marker to assess gene flow. Outcrossing was mainly concentrated to the downwind areas of the recipient fields with a pronounced edge effect. The application of a general linear mixed effect model showed that there was no significant effect of the gap crop type on the amount of pollen-mediated gene flow. It is concluded that the crop type planted between GM and non-GM maize has no major importance for the development of coexistence measures. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) is an important turfgrass species used for lawns, sports fields, and recreational areas. Insufficient tolerance to subfreezing temperatures compromises its persistence in northern climates. A recurrent selection method, entirely performed indoors, was applied to two initial genetic backgrounds to generate populations putatively more tolerant to freezing (TF populations). The objective of the present study was to assess physiological and molecular responses after four cycles of selection (TF1-TF4). Freezing tolerance and cold-induced metabolites were monitored in plants hardened to natural variations in temperatures in fall and winter in an unheated greenhouse. Recurrent selection improved freezing tolerance expressed as the lethal temperature for 50% of the plants (LT50) and the vigor of regrowth after freezing. Significant changes in the levels of total and individual cold-induced carbohydrates (fructans) and amino acids (glutamine and proline) in crowns of hardened plants occurred in response to selection. Both groups of metabolites showed an opposite response to selection. The observation of DNA polymorphisms and progressive genetic differentiation between the initial populations and advanced cycles of selection suggests an impact of selection on allelic composition. Recurrent selection had a positive impact on freezing tolerance of perennial ryegrass through modifications in the molecular and genetic makeup of the populations. [ABSTRACT FROM AUTHOR]

Research on the effects of potassium (K) fertilization on turfgrass growth and its relationship to tissue K and soil K have been inconsistent due to the many factors affecting tissue K such as nitrogen (N) fertilization. This 5-yr study was initiated in 2004 to better understand N (as urea) and K (as K2SO4) effects on soil and plant response of perennial ryegrass (Lolium perenne L. 'Brightstar'). A field study was conducted to evaluate five rate levels of N (49, 147, 245, 343, or 441 kg ha-1 yr-1) with three rate levels of K (49, 245, or 441 kg ha-1 yr-1). Clipping yield (CY), leaf tissue K, soil pH, rooting (in 2004 and 2005 only), and soil K were assessed in spring of each year. Leaf K and soil K increased linearly with K applied, whereas leaf K and CY regression slopes with soil K increased with greater N applied. Leaf K and CY increased linearly with N, whereas rooting, soil pH, and soil K decreased linearly with increased N. Rooting was inversely related to CY. Luxury consumption of K was observed in the latter years of the test (2006) at N rates of 245 kg N ha-1 yr-1 and lower. The strength of the regression (r²) and covariation between CY and leaf K increased with N rate and decreased with year of the test. There were no observed changes in shoot and root growth in response to K fertilization even at low soil test K levels (50 mg kg-1). [ABSTRACT FROM AUTHOR]

The expression of elevated water-soluble carbohydrate (WSC) concentrations in perennial ryegrass (Lolium perenne L.) cultivars selected for high forage WSC concentration can be highly variable across environments. Our aim was to determine whether N application rate influences the expression of the high WSC phenotype. Cultivars AberDart (selected for high WSC concentration) and Fennema (control) were evaluated across four fertilizer N application rates (0,40, 80, and 120 kg ha 1 per harvest) over four replicates and 2 yr at Grange, Ireland, and Saerheim, Norway. Plots were managed for silage production with four cuts per year in Ireland and three cuts per year in Norway. Nine forage traits were measured: WSC, dry matter digestibility, crude protein, buffering capacity, dry matter, ash, dry matter yield, N use efficiency, and apparent N recovery. The response of AberDart and Fennema to N application rate was predominantly similar within and over years and locations for all traits. Differences between cultivars in WSC concentration were largely consistent across N application rates, years, and locations. AberDart had mean WSC concentrations 8 to 12% higher than Fennema depending on harvest. Present results suggest that the evaluation and selection of perennial ryegrass for high concentrations of WSC in cool-temperate maritime climates may be conducted across a wide range of N application rates and, by extension, soil N supply rates. [ABSTRACT FROM AUTHOR]

Orchardgrass (Dactylis glomerata L.) acreage has declined compared to perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca amndinacea Schreb.). With the intent of developing new sources of orchardgrass germplasm, 162 half-sib families from six orchardgrass germplasm populations and three orchardgrass cultivars were evaluated during 2008 for maturity and plant morphology at locations in Idaho and Utah. Genetic similarity of the populations was also characterized using simple sequence repeat markers. Genetic variation between families differed from zero for seven of the nine traits evaluated, with broad-sense heritability estimates ranging from 0.26 (flag leaf width) to 0.74 (maturity). For each trait that exhibited genetic variation, half-sib families were identified that possessed trait values similar to or more extreme than the values corresponding to the included commercial orchardgrass cultivars. Through principle component analysis, potential groupings of half-sib families with similar phenotypic characteristics were identified; for example, taller plants with earlier maturity. Therefore, germplasm could be targeted for development of improved orchardgrass with maturity and morphology suitable to specific management practices, such as short stature, narrow leaves, and late maturity for mixture with legumes. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) is considered a premier turfgrass and forage grass worldwide yet susceptibility to freezing damage limits its use. C-repeat binding factor (CBF) dehydration-responsive element-binding protein (DREB) related genes are considered important for the regulation of abiotic stress in plants. In this study, CBF DREB-related genes in perennial ryegrass, also known as LpCBF genes, were resequenced from cultivated and landrace plants from a worldwide collection. A total of 109 plants survived clonal propagation and were tested for freezing tolerance. The resulting data was subjected to mixed model analysis to determine whether the freezing tolerance is related to single nucleotide polymorphism (SNP) and indel markers within two genes, LpCBFIIIb and LpCBFIIIc. One major quantitative trait locus (QTL) was discovered in LpCBFIIIc for freezing tolerance, with the majority of the plants possessing the superior allele. Several minor loci were also discovered in this gene, but no significant loci were discovered in LpCBFIIIb. [ABSTRACT FROM AUTHOR]

Cool-season legumes have potential to replace Ν fertilizer in annual cool-season grass pastures, thus improving returns to producers. The objective of this 3-yr study was to compare the performance and economics of stocker cattle (Bos spp.) grazing rye (Secale cereale L.)- annual ryegrass (Lolium multiflorum Lam.) under two Ν systems. Paddocks were planted in early September 2008 through 2010 and contained rye-annual ryegrass with 112 kg Ν ha-1 (fertilized so that a total of soil residual Ν plus fertilizer Ν would equal 112 kg Ν ha-1) (RR-N) or contained a rye-annual ryegrass with annual legume mixture (arrowleaf clover [Trifolium vesiculosum Savi], field pea [Pisum sativum L], and hairy vetch [Vicia villosa Roth]) (RR-Leg). Steers (307 ± 55 kg initial body weight) were weighed every 28 d and stocking rates were adjusted based on forage mass with put-andtake steers. Forage mass, forage allowance, and stocker average daily gain (ADG) and total gain (TG) were measured every 28 d. Results show similar performance between RR-N and RR-Leg systems in grazing days (average 367 d ha-1), ADG (average 1.065 kg per head d-1), and TG (average 390 kg ha-1). While the 3-yr average total cost associated with the RR-N system (US$569.88 ha-1) was greater than the RR-Leg system ($550.57 ha-1), there were no differences in gross revenue (average $815.91 ha-1) or expected net returns (average $255.68 ha-1) between systems. Annual legumes could be a viable replacement for commercial Ν fertilizer in rye-annual ryegrass pastures although adoption may be limited due to ease of Ν fertilizer application. [ABSTRACT FROM AUTHOR]

Overseeding warm-season perennial grasses with annual ryegrass (Lolium multiflorum Lam.) is a common practice throughout the southeastern United States to extend the grazing season with high quality forage. 'Coastal' bermudagrass [Cynodon dactylon (L.) Pers.] competition to overseeded annual ryegrass was determined by light reaching the soil surface, ryegrass seedling density, and ryegrass herbage production. Treatments were 0, 56, and 112 kg ha-1 N 6 to 8 wk before planting ryegrass and sod management practices (SMPs) of a shallow disking (2.5 to 5.0 cm), applying a desiccant, and a control before planting in combination with mowing to a 2.5 or 10.0-cm sod height (SH) for 3 yr. Applying N 6 to 8 wk before planting did not influence any of the plant parameters measured. The shallow disking SMP and 2.5-cm SH allowed the most light to reach the soil surface and had the greatest ryegrass seedling density. At the 10-cm SH the shallow disking SMP had a greater seedling density than the desiccant and control SMP. None of the SMP-SH combinations consistently improved first harvest or annual herbage mass yields over the control at the 2.5-cm SH. Significant differences may have occurred if the first harvest was taken earlier. Spring bermudagrass recovery was reduced by the shallow disking SMP and 2.5-cm SH. At a bermudagrass SH of 10 cm or less there was little advantage to disking or using a desiccant to enhance ryegrass production. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) is a coolseason turfgrass susceptible to low temperature injury. Wilt-based irrigation (WI) is a common practice for scheduling irrigation to turf by allowing a mild, negative water imbalance to occur as an alternative to maintaining turf under nonlimiting soil moisture. Moisture stress has been shown to promote freezing tolerance but this has not been investigated in response to WI. Objectives of this study were to examine perennial ryegrass in response to WI (applied at 50% visual leaf roll) on freezing tolerance (median lethal temperature at 50% survival [LT50]), 13C discrimination (Δ), internal leaf-to-ambient CO2 concentration (ci:ca) ratio, leaf water, rooting, water use efficiency (WUE), and wilting tendency (days to wilt and number of wilt events) among three top-performing (TP) and three bottomperforming (BP) perennial ryegrass cultivars. Cultivars were selected based on turf quality trials from a northern location (Orono, ME). Plant measurements were made in the greenhouse in 2007 and 2008 comparing the first (single) and last (multiple) wilt cycle after 68 d of irrigation between well watered and WI. Multiple wilt exposures significantly enhanced freezing tolerance compared to a single wilt event for IP cultivars only, but gains in freezing tolerance were small (<1.0°C). Freezing tolerance (lower LT50 values) was generally associated with lower yield, WUE, and leaf water content. In some TP cultivars, wilt-induced freezing tolerance was associated with greater wilting tendency and drought sensitivity indicated by lower Δ values and ci:ca ratio. Repeated wilt exposures increased rooting over a single wilt event. [ABSTRACT FROM AUTHOR]

Many organic products have been used effectively in turfgrass management programs, but their exclusive use in athletic field maintenance and effect on playing surface quality has not been extensively researched. The objectives were to determine the effects of management regimes and overseeding during simulated traffic on (i) turfgrass color and quality, (ii) percent cover, and (iii) weed populations. The experimental design was a 2 × 6 factorial, with two overseeding levels (overseeded and not overseeded) of a perennial ryegrass (Lolium perenne L.) blend during traffic and six management regimes: (i) conventional, (ii) organic manure (OMan), (iii) organic protein (OPro), (iv) organic manure plus compost tea (OMan+CT), (v) organic protein plus compost tea (OPro+CT), and (vi) none or the control. This research was conducted over 2 yr on a mature stand of 'Langara' Kentucky bluegrass (Poa pratensis L.) on a Paxton sandy loam soil. Fall traffic was simulated with a Cady Traffic Simulator. The conventional treatment consistently produced higher quality turfgrass, lower weed counts, and better mid- to late-fall color. Weed populations were significantly less with the conventional regime. Overseeding increased cover at the end of the traffic periods by 32% in the first year and by 103% in the second year. Overseeding was also beneficial to turfgrass color and quality and in reducing weeds. The conventional treatment also retained significantly higher turfgrass cover than the organic regimes under trafficked conditions late into the fall in 2008. However, no difference in late fall cover between the conventional and organic management regimes was observed in late fall 2009. Compost tea applications showed no enhancement of turfgrass color, quality, or cover over the entire duration of the study. [ABSTRACT FROM AUTHOR]

Stocking rate can affect production and persistence of bermudagrass ICynodon dactylon (L.) Pers.] pastures. 'Coastal' and common bermudagrass pastures were grazed at different stocking rates to maintain specific low, medium, and high herbage mass (HM) during a 38-yr period. From 1969 to 1984, pastures received identical fertilization, and from 1985 to 2005, regimens of N plus annual ryegrass (Lolium multiflorum Lam.) vs. no N plus clover (Trifolium spp.) were superimposed on each bermudagrass x HM. Stand of both Coastal and common bermudagrass was negatively affected by decreasing HM and no N fertilizer. Bahiagrass (Paspalum notatum Fluggé) was the primary non-bermudagrass invasive species on no-N pastures. Invasive bermudagrass ecotypes were more abundant at 73 to 86% on low HM Coastal with clover or ryegrass, respectively. On common bermudagrass, ecotypes were present at about 25 and 40%, respectively, on clover and ryegrass but not affected by HM. During October 2005, 125 whole plant-root core eGotypes were collected and fingerprinted using amplified fragment length polymorphism (AFLP) markers, analyzed via coefficient of genetic similarity matrix, and clustered in genetically related groups. Four groups were identified in Coastal and five in common bermudagrass. The Coastal and Coastal-similar ecotypes were different from common bermudagrass and common bermudagrass-similar ecotypes in plant height, leaf length, leaf width, and leaf coarseness. Plant inflorescence characteristics of ecotype ranked similar to those of growth traits. The bermudagrass were most sustainable under moderate to high HM and with N fertilization. [ABSTRACT FROM AUTHOR]

Nitrogen enhances annual ryegrass (Lolium multiflorum Lam.) growth on the infertile Coastal Plain soils in the southeastern United States but N can be antagonistic to clovers. Nitrogen rate and time of application were evaluated on an arrowleaf clover (Trifolium vesiculosum Savi.)- annual ryegrass mixture growing on a Coastal Plain soil for 3 yr in northeast Texas. Fertilizer treatments were 0, 34, 67, or 101 kg N ha-1 at planting or first true clover leaf (FCL) stage followed by 0 or 67 kg N ha-1 in December and March. Planting, FCL, and December N applications enhanced ryegrass production but had little effect on arrowleaf clover production by mid March. The general trend was for clover percentage and yield to decrease and ryegrass yield to increase as the total amount of N fertilizer applied increased. The no-N treatment always had the greatest percentage clover usually followed by single N application treatments with clover percentages greater than 50%. Average annual yield of ryegrass alone without N was 1139 kg ha-1 compared to 4038 kg ha-1 with 201 kg N ha-1. Applying 67 kg N ha-1 at FCL and in December and March was always one of the most productive N treatments. Applying 67 kg N ha-1 only twice at FCL and in December was the best compromise for maintaining a high clover percentage and clover-ryegrass yield and was always equal to ryegrass alone with three appli- cations of 67 kg N ha-1. [ABSTRACT FROM AUTHOR]

For perennial forage grasses, tillering and shoot elongation are important developmental events to determine grassland production. To thoroughly identify and characterize quantitative trait locus (QTL) regions controlling the events, a perennial ryegrass (Lolium perenne L.) mapping population comprising 188 F2 individuals was evaluated for tiller number (TN), plant length (PL), and leaf length (LL) over 12 cuts in replicated field and pot experiments in Sapporo, Japan, during 2 yr. Quantitative trait loci were repeatedly detected in 16 genomic regions. Based on the QTL, 10 regions affected both shoot elongation (PL and LL) and tillering (TN), whereas only six regions had a single effect on either event. Five QTL regions mapped on linkage groups 1, 2, 5, and 6, explaining at maximum 34 to 56% phenotypic variance, likely contain key genes for plant development. Profiles (e.g., direction and magnitude) of QTL effects differed greatly among most regions, indicating a large diversity among the genes involved. Statistical tests revealed significant interaction effects of genotype with growth condition and cut for all QTL regions. The QTL positions were compared with those reported for ryegrass and rice, suggesting the presence of genes identical to the current population and semiwild perennial forage grasses. The current QTL analysis indicated that the control of ryegrass plant development involves diverse, unique genes whose effects are enhanced or suppressed by growth environment and foliage cutting. [ABSTRACT FROM AUTHOR]

The most serious foliar disease of perennial ryegrass (Lolium perenne L.) is crown rust (caused by Puccinia coronata Corda f.sp. b/u Brown). Progress in resistance breeding using recurrent selection has been slow, due to lack of genetic knowledge. Puccinia coronata is a basidiomycete fungus with a complex life-cycle involving bbth asexual and sexual reproductive modes. Pathotype variation may exist, but confirmation is complicated by the outbreeding nature of the host grass and consequent intrapopulation diversity. Qualitative and quantitative resistance mechanisms may hence be due to either major resistance genes responding to mixed pathogen populations, or minor (quantitative) resistance genes. Advances in molecular biology have permitted analysis of both host and pathogen genetics. Development of pathogen-derived simple sequence repeat (SSR) genetic markers allowed detailed analysis of genetic variation, as well as generation of homogenized inoculum for detailed trait-dissection studies. Multiple genomic regions were identified as containing quantitative trait loci (QTLs) for pathogen resistance, and specific single nucleotide polymorphism (SN P) markers for defense response (DR) and disease resistance (R) genes have been evaluated for QTL co-location. The current knowledge status of the crown rust pathogen and genetics of host resistance is reviewed, as well as future prospects for facilitated rust resistance breeding. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) is a coolseason turfgrass species that can exhibit significant freezing injury in northern climatic regions. The objective of this study was to quantify major physiological and biochemical changes occurring during the cold acclimation period in four perennial ryegrass accessions varying in freezing tolerance (two freezing-tolerant accessions, TOL-1 and TOL-2, and two freezing-susceptible accessions, SUS-1 and SUS-2). Plants were subjected to a cold acclimation period of 2°C for 21 d in a controlled environment chamber. Crown tissues were harvested at 0, 7, 14, and 21 d of acclimation for determination of proline, water soluble carbohydrates (WSC), and lipid composition. Leaf photochemical efficiency (Fv/Fm) was also measured weekly before plant sampling for biochemical components. In general, proline levels increased and Fv/Fm decreased during cold acclimation; however, there were no differences in proline accumulation or FyI Fm among the accessions in response to cold acclimation. Water soluble carbohydrates significantly increased in response to 2°C, with TOL accessions (TOL-1 and TOL-2) accumulating higher WSC than SUS (SUS-1 and SUS-2) by 21 d of acclimation. There were also significant changes in major phospholipids classes at 2°C. Specifically, TOL-2 exhibited a higher ratio of membrane stabilizing lipids and unsaturated fatty acid content compared to SUS-1, SUS-2, and TOL-1 by 21 d of cold acclimation. [ABSTRACT FROM AUTHOR]

Wear tolerance is important in sports turf, but the effects of nitrogen (N) and potassium (K) on wear mechanisms in perennial ryegrass (Lolium perenne L.) are unknown. The objective of this study was to evaluate wear mechanisms in response to N and K in this species. Field studies were conducted in 2006 and 2007 using five N levels (49, 147, 245, 343, and 441 kg ha-1 yr-1) in combination with three rate levels of K (49, 245, and 441 kg ha-1 yr-1). Wear was applied in both years using wear simulators. Ten plant characteristics were measured in field plots. Nitrogen had significant effect on wear tolerance and plant characteristics. Shoot growth accounted for as much as 94% of the variation in wear tolerance (r = -0.97, p ⩽ 0.001). Tissue moisture measured as relative water content and shoot water content covaried with shoot growth. Wear injury, shoot growth rate and tissue moisture increased with increasing N, especially when fertilized in excess of 245 kg N ha-1 yr-1. Tissue moisture explained as much as 66% (r = -0.81, P ⩽ 0.001) of the variation in wear tolerance. Cell wall components, leaf strength, and shoot density were secondary in explaining wear tolerance. Verdure was not important. Tissue K and soil-available K were not correlated with wear tolerance. These results suggest fertilizing at no more than 245 kg N ha-1 y-1 to maintain optimum wear tolerance, shoot growth rate and tissue moisture. [ABSTRACT FROM AUTHOR]

Fertility may influence wear tolerance and recovery, but its effects on perennial ryegrass (Lolium perenne L.) are unknown. Our objective was to evaluate the effects of nitrogen (N) and potassium (K) on wear tolerance and recovery in perennial ryegrass. Field studies were conducted in 2006 and 2007 to evaluate five rate levels of N (49, 147, 245, 343, and 441 kg ha-1 yr-1) with three rate levels of K (49, 245, and 441 kg ha-1 yr-1). Wear was applied using differential slip wear (DSW) and grooming brush wear (GBW). Injury was assessed using visual ratings and a relative chlorophyll index from spectral readings measured on wear-treated and nontreated plots. Grooming brush wear was ineffective for assessing recovery. Wear tolerance ratings between GBW and DSW were correlated with r-values as high as 0.93 (P ⩽ 0.001). Reflectance readings were correlated with GBW and DSW ratings. Nitrogen influenced wear tolerance and recovery. Wear tolerance decreased linearly as N increased, and N accounted for as much as 95% of the treatment variation. Reductions in wear tolerance with increasing K were observed with GBW, while significant gains in recovery from DSW were observed with K at 2 wk after treatment (2WAT). Nitrogen in excess of 245 kg ha-1 yr-1 promoted reductions in wear tolerance but faster recovery. The 245 kg N ha-1 yr-1 rate afforded full recovery in the shortest interval as early as 8WAT. Optimum N for maximum wear tolerance and recovery for perennial ryegrass is 245 kg N ha-1 yr-1. [ABSTRACT FROM AUTHOR]

Timely assessments of nutritive values of legume-based swards during the growing season can facilitate a targeted and site-specific forage management. This study was undertaken to explore the potential of field spectral measurements for a nondestructive prediction of metabolizable energy, ash content, crude protein (CP), and acid detergent fiber of legume-grass mixtures. A population of 200 legume-grass swards (Lolium perenne L., Trifolium repens L., Trifolium pratense L.) representing a wide range of legume proportion (0-100% of dry matter), and growth stages (beginning of tillering to end of flowering) were used in this investigation. The paper examines three techniques for analysis of the hyperspectral data set (350-2500 nm): two-waveband reflectance ratios, modified partial least squares (MPLS) regression, and stepwise multiple linear regression (SMLR). Forage quality variables had weak relationships with the developed reflectance ratios, whereas hyperspectral analysis by MPLS and SMLR resulted in high precision (0.70 ⩽ R² ⩽ 0.94). Even with a reduced spectral data set (630-1000 nm), estimates of MPLS and SMLR models were still acceptable for forage ash (0.62 ⩽ R² ⩽ 0.78) and CP (0.83 ⩽ R² ⩽ 0.86), a finding that could facilitate an application of field spectroscopy with more simple sensors. Estimates of ash and CP were further improved by legume-specific calibrations. [ABSTRACT FROM AUTHOR]

Digital image analysis could be a rapid and precise technique for estimating legume proportions in grass swards. In 2004, we conducted a pot study to evaluate a digital image analysis (DIA) system for estimation of legume dry matter (DM) contribution in legume-grass mixtures. Examination of pure swards and binary legumegrass mixtures of red clover (Trifolium pratense L.), white clover (T repens L.), alfalfa (Medicago sativa L.), and perennial ryegrass (Loliumperenne L.) took place after 35, 49, and 63 d of growth. To estimate the cover percentage of legumes in the swards, a total of 64 digital pictures were taken. The DM contribution of legumes (% of total biomass) showed a significant relationship with the proportion of image area covered by legumes (% of total area), which was classified visually. A DIA system for grayscale images was developed with the software Optimas. We found that DIA could be used to accurately predict legume contribution in mature swards. Legume contribution, as estimated by DIA, was significantly correlated with DM contribution of red clover (R² = 0.87), white clover (R² = 0.85), and alfalfa (R² = 0.79). Bare ground reduced the predictive ability of DIA in young or open swards. Use of DIA may be limited until we refine the method to deal with bare ground and different leaf shapes associated with various weed species. [ABSTRACT FROM AUTHOR]