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One possible approach for improving the nitrogen (N)‐use efficiency of perennial ryegrass (Lolium perenne L.) pastures and reducing environmental N losses is to select cultivars or incorporate alternative pasture species with lower shoot N concentrations. Viability of this strategy depends on herbage production not being unduly compromised. A pot experiment compared the shoot N concentration requirements of a diverse range of perennial ryegrass cultivars to achieve 90% and 99% of the herbage yield maxima achievable within a 20 day regrowth cycle. This research was undertaken to quantify if and what effect Australasian breeding programs have had on the N nutrition of perennial ryegrass. Our experiment found minimal genetic variation in the shoot N concentration requirements for vegetative perennial ryegrass swards to achieve near‐maximum herbage yields of living biomass. Across evaluated cultivars, swards achieving 90% and 99% of herbage yield maxima required minimum shoot N concentrations (on a dry matter basis) of 2.56% and 2.87%, respectively. Our experiment also evaluated the shoot N concentration requirements of modern summer‐active cocksfoot (syn. orchardgrass; Dactylis glomerata L.) and tall fescue (Festuca arundinacea Schreb.) ecotypes. We found their shoot N concentration requirements to achieve optimal herbage growth to be similar to those of perennial ryegrass. Taken together, our results suggest that within the perennial ryegrass genome, and among similar high yielding temperate perennial grasses, there may be limited scope for selecting plants with lower shoot N concentration requirements. [ABSTRACT FROM AUTHOR]

Outcomes of weed biological control projects are highly variable, but a mechanistic understanding of how top-down and bottom-up factors influence the success of weed biological control is often lacking. We grew Rumex obtusifolius, the most prominent native weed in European grasslands, in the presence and absence of competition from the grass Lolium perenne and subjected it to herbivory through targeted inoculation with root-boring Pyropteron spp. To explore whether the interactive effects of competition and inundative biological control were size-dependent, R. obtusifolius was planted covering a large range of plant sizes found in managed grasslands. Overall, competition from the grass sward reduced aboveground biomass and final root mass of R. obtusifolius about 62- and 7.5-fold, respectively, and increased root decay of R. obtusifolius from 14 to 58%. Herbivory alone increased only root decay. However, grass competition significantly enhanced infestation by Pyropteron spp. and, as a consequence, enhanced the impact of herbivory on aboveground biomass and final root mass. The synergistic effect was so strong that R. obtusifolius plants grown from initially smaller roots did no longer develop. Inoculating R. obtusifolius with Pyropteron species in grasslands should be further pursued as a promising inundative biological control strategy in the weed's native range. [ABSTRACT FROM AUTHOR]

Perennial grasses have got greater attention in the past decade due to their potential to be productive over several years and their positive impacts on the environment. A great resource in this regard are the native species, which are well adapted to the specific conditions of the environment, but are often underestimated and irrationally used. The objects of study in the present research were 8 grasses (Festuca rubra, Lolium perenne, Dactilis glomerata, Arrhenatherum elatius, Festuca arundinacea, Briza maxima, Trisetum flavescens, Agrostis alba), typical for the Middle Balkan Mountains region, in order to assess their productivity and stability. The two-factor analysis of variance in terms of dry mass yield revealed significant influence of the factors of species, environment, and their interaction. During the 9-year experimental period, the highest yield was demonstrated by F. rubra (5.75 t ha-1), followed by F. arundinacea (5.54 t ha-1) and A. elatius (5.43 t ha-1). The stability parameters, calculated by the methods of regression analysis defined as stable the species of A. elatius and A. alba, and those, calculated by variance and non-parametric analyzes - F. rubra, D. glomerata and F. arundinacea. Differences in the stability assessment of the individual parameters are due to the fact that the different methods are based on different concepts of stability. The GGE biplot analysis, which integratedly assesses the species for their productivity and stability, identified F. arundinacea and A. elatius as the most favorable combining of these indicators. Trisetum flavescens was also characterized by good stability and average productivity. These species are suitable for cultivation in a wide range of environmental conditions. [ABSTRACT FROM AUTHOR]

Autumn closing date (CD) in intensive pasture‐based systems influences spring herbage availability. Little is known about the impact of earlier closing of swards in autumn on sward structure. A two‐year experiment was undertaken to investigate the impact of five CD on herbage production, leaf extension rate (LER), leaf senescence rates (LSR), sward free leaf lamina (FLL) content and the production and survival of tillers over winter and into spring. The five CD ranges were October 1–15 (CD1), October 16–30 (CD2), October 31––November 14 (CD3), November 15–29 (CD4), November 30–December 14 (CD5) and sward measurements were made on four measurement dates (MD): December 11 (MD1), January 6 (MD2), January 27 (MD3) and prior to spring defoliation (MD4). Thirty perennial ryegrass tillers were measured until the first defoliation in spring (average 1 March). Herbage mass was greatest in early CD and tillers had greater LER and LSR (4.6 and 4.5 mm tiller−1 day−1 respectively) compared to swards with a later CD (3.2 and 2.3 mm tiller−1 day−1 respectively). Early CD had greater parent and daughter tiller mortality than later CD (parent tiller mortality 1.1 and 0.3 ± 0.19 tillers; daughter tiller mortality 1.1 and 0.3 ± 0.27 tillers respectively). Early CD also had greater LER and LSR in daughter tillers (2.6 and 1.5 mm tiller−1 day−1, respectively) compared to late (1.5 and 0.5 mm tiller−1 day−1, respectively). Earlier closing of sward increased herbage mass in spring, however, there were negative implications, such as increased LSR and tiller mortality. [ABSTRACT FROM AUTHOR]

Low dietary energy and decreased intake of herbage have been attributed to the reduced performance of grazing dairy cattle. We hypothesized that grasses with inherently greater energy would interact in a complementary way with condensed tannins (CT) in birdsfoot trefoil to increase herbage intake by grazing dairy heifers. Eight pasture treatments comprising high-sugar perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata L.), meadow bromegrass (Bromus riparius Rehmann), and tall fescue [ Schendonorus arundinaceus (Schreb.) Dumort] were established in Lewiston, Utah as monocultures and binary mixtures with birdsfoot trefoil (Lotus corniculatus L.; BFT). Pasture treatments were rotationally stocked by Jersey heifers for 105 d in 2017 and 2018, and herbage samples were collected pre- and postgrazing for each 7-d grazing period and analyzed for herbage mass, nutritive value, and apparent herbage intake. We observed differences among pasture treatments in herbage quantity and nutritive value, as well as differences in herbage intake by grazing Jersey heifers. On average, grass-BFT mixtures had greater herbage intake than grass monocultures, and every grass-BFT treatment individually had greater herbage intake than their respective grass monocultures. Using multivariate analyses, we determined that approximately 50% of the variation in herbage intake was due to nutritive and physical herbage characteristics, with the most explanatory being characteristics related to fiber and energy, followed by those related to the percent of BFT in the herbage. Grass monocultures exhibited a range of inherent dietary energy, but there was indication that an imbalance of energy to crude protein (e.g., protein deficient) reduced intake of grass monocultures. Moreover, there was some evidence of a complementary effect between increased dietary energy and CT; however, low CT levels made it impossible to determine the effect of CT on herbage intake per se. This study confirmed that chemical and physical characteristics inherent to different pasture species have a large effect on herbage intake by grazing cattle. Pastures planted to binary mixtures of nutritious grasses and birdsfoot trefoil increase herbage intake of temperate pastures by grazing Jersey heifers. [ABSTRACT FROM AUTHOR]

BACKGROUND This study aimed to evaluate the effect of l‐tryptophan (l‐TRP) used in the cultivation of Lolium perenne on the yield, and chemical and microbiological quality of its herbage and silage. l‐Tryptophan was applied in doses of 5, 0.5, 0.05 kg ha−1. The experiment was conducted with a control group (C) and a comparative control group (C+) with higher nitrogen fertilization. RESULTS: The dose of 5 kg ha−1 had a significant effect on herbage yield, which increased by 15% compared to group C and approximated the value achieved in group C+. The treatment with l‐TRP caused a significant increase in water‐soluble carbohydrate (WSC) content only in Tr5 (165 g kg−1 DM), which was reflected in a more beneficial course of fermentation, lower pH (4.59), and a higher sum of fermentation acids, including lactic acid (94.7 g kg−1 DM). Ryegrass treatment with a high l‐TRP dose effectively reduced the loads of Clostridium spp. and fungi, and increased the count of Bacillus spp. The l‐TRP significantly reduced N‐NH3 content in Tr05 (98.6 g kg−1 TN) compared with C+ (123 g kg−1 TN) and butyric acid content in Tr05 (from 1.35 g kg−1 DM in the C to 0.38 g kg−1 DM). CONCLUSION: The most effective dose turned out to be a dose of 5 kg ha−1, which allowed a higher yield and a better fermentation course to be achieved. This work presents the feasibility of using l‐TRP to optimize nutrient consumption by Lolium perenne and ultimately to affect the quality of its silage as a feedstuff. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Ergot, caused by Claviceps purpurea sensu lato, is an economically important seed replacement disease of Kentucky bluegrass (Poa pratensis) and perennial ryegrass (Lolium perenne) seed crops. C. purpurea sensu stricto is considered the primary Claviceps species responsible, but genetic diversity and cryptic species within C. purpurea sensu lato have previously been reported. Fifty-six C. purpurea sensu lato isolates collected from P. pratensis (n = 21) and L. perenne (n = 35) in Oregon and Washington between 2010 and 2014 were characterized via random amplified polymorphic DNA (RAPD), partial internal transcribed spacer (ITS), β-tubulin and elongation factor-1α (EF-1α) sequences, conidial size, and ergot alkaloid chemotype. Based on RAPD analysis, seven isolates from P. pratensis and 33 isolates from L. perenne collected in Oregon corresponded to C. purpurea sensu stricto, and 13 isolates collected from P. pratensis in Washington and Oregon were identified as C. humidiphila. Partial ITS, β-tubulin, and EF-1α sequences identified 10 isolates from P. pratensis as C. humidiphila, and seven isolates from P. pratensis and 33 isolates from L. perenne were identified as C. purpurea sensu stricto. Several isolates generated ambiguous RAPD bands or sequences that prevented identification. Ergot alkaloid chemotype profiling found that ergocornine and its epimer were predominant in sclerotia from P. pratensis, whereas ergotamine and its epimer were most abundant in sclerotia from L. perenne. This study confirms the presence of the C. purpurea sensu lato species complex in the U.S. Pacific Northwest and suggests that more research is needed to characterize and mitigate Claviceps spp. infection of grass seed crops in North America. [ABSTRACT FROM AUTHOR]

Field indicators of forage nutritive value could help farmers with rapid management decisions to optimize timing and intensity of grazing and meet objectives regarding animal nutrition. The objective of this research was to evaluate the likely relationships among leaf blade nutritive value, herbage mass and leaf stage of pasture regrowth under different growing seasons and residual sward heights. Experiments were performed on perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) pastures during spring and summer of 2016. In both pastures, three residual sward height treatments (3, 6 and 12 cm) were imposed on plots arranged in a split plot design, replicated in three blocks. Sward plots were harvested 5–6 times at intervals spaced 7–10 days apart to measure herbage mass, plant morphology, neutral detergent fibre (NDF), and the 24‐hr in vitro digestibility of NDF (NDFD) and dry matter (DMD) of leaf blades. Pastures showed strong (R2:.62 to.70), but variable, negative relationships between NDFD and herbage mass that varied with the rate at which pasture grew in each season of experimentation. Although there was a consistent NDFD decline as leaf stage of regrowth progressed (R2:.75 to.97), the NDFD also decreased as residual sward height increased, most notably in tall fescue. Additionally, findings indicate that the greater leaf length plasticity of tall fescue compared to residual sward heights may offer opportunities to manage both post‐ and pre‐grazing targets to achieve tall fescue forages with a similar high nutritive value as perennial ryegrass. However, the evaluation of this hypothesis at the farm level and its impacts on animal intake and performance warrants further careful investigations. [ABSTRACT FROM AUTHOR]

The aim of this paper is to evaluate the effect of different doses of spent mushroom substrate and cow slurry on sugar content and digestibility of hybrid alfalfa and grass mixtures. The main factors were different doses of organic material: mushroom substrate and slurry, and the following legume grass mixtures: M1-orchard grass (Dactylis glomerata), perennial ryegrass (Lolium perenne), and hybrid alfalfa (Medicago x varia T. Martyn); M2-orchard grass, hybrid alfalfa; M3-perennial ryegrass, hybrid alfalfa. In each growing season, the mixtures were harvested three times during three years of their full use. Sugar content and dry matter digestibility were determined with near-infrared spectroscopy (NIRS) using the NIRFlex N-500 spectrometer. Of all fertilizer treatments, the application of mushroom substrate at a dose of 20 t·ha−1 in combination with 40 m3 of slurry resulted in the best forage quality with its highest digestibility. In the mixture of perennial ryegrass and hybrid alfalfa increasing doses of mushroom substrate with decreasing doses of slurry lowered soluble sugar content and digestibility. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) provides a cost-effective forage species for New Zealand farms. Vegetative persistence (maintained herbage growth and survival without reseeding) is an important trait for decreasing costs of pasture establishment. Breeding for vegetative persistence is difficult because of a deficiency of long-term trials to observe the complex interactions between plant genotype and environment. Over time in a long-term trial, a shift in the genetic mean of a cultivar could occur as plants with genetically enhanced persistence traits survive. This study aimed to identify a shift in the genetic mean of two cultivars sown in a long-term trial in Hawkes Bay, New Zealand. Plots of 1 m rows were assessed in a trial for 13 months to compare changes in additive genetic variation ( σ a 2 ), narrow-sense heritability ( h n 2 ), and trait associations of half-sib (HS) populations generated from "Persistent" plants and commercially bought seed of "Original" cultivars Grasslands Samson and Commando. Significant (P < 0.05) σ a 2 and high levels of h n 2 for some populations were identified for scores of herbage growth, leaf width, plant habit and aftermath heading. This study found genetic shifts over time were cultivar specific. Traits that were different between Persistent and Original populations were previously associated with decreased pasture intake. Trait associations and cluster analysis identified HS families that could be used for developing enhanced persistence. [ABSTRACT FROM AUTHOR]

Meadow fescue (Festuca pratensis Huds.) is one of the most important forage grasses in temperate regions. It is a diploid (2n = 14) outbreeding species that belongs to the genus Festuca. Together with Lolium perenne , they are the most important genera of forage grasses. Meadow fescue has very high quality of yield with good winter survival and persistency. However, extensive genomic resources for meadow fescue have not become available so far. To address this lack of comprehensive publicly available datasets, we have developed functionally annotated draft genome sequences of two meadow fescue genotypes, 'HF7/2' and 'B14/16', and constructed the platform ForageGrassBase, available at http://foragegrass.org/ , for data visualization, download and querying. This is the first open-access platform that provides extensive genomic resources related to this forage grass species. The current database provides the most up-to-date draft genome sequence along with structural and functional annotations for genes that can be accessed using Genome Browser (GBrowse), along with comparative genomic alignments to Arabidopsis , L. perenne , barley, rice, Brachypodium and maize genomes. We have integrated homologous search tool BLAST also for the users to analyze their data. Combined, GBrowse, BLAST and downloadable data gives a user-friendly access to meadow fescue genomic resources. To our knowledge, ForageGrassBase is the first genome database dedicated to forage grasses. The current forage grass database provides valuable resources for a range of research fields related to meadow fescue and other forage crop species, as well as for plant research communities in general. The genome database can be accessed at http://foragegrass.org. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne) is a forage and amenity grass species widely cultivated in temperate regions worldwide. As such, perennial ryegrass populations are exposed to a range of environmental conditions and stresses on a seasonal basis and from year to year. One source of potential stress is limitation on water availability. The ability of these perennial grasses to be able to withstand and recover after periods of water limitation or drought can be a key component of grassland performance. Thus, we were interested in looking at changes in patterns of gene expression associated with increasing water stress. Clones of a single genotype of perennial ryegrass were grown under non-flowering growth room conditions in vermiculite supplemented with nutrient solution. Leaf and root tissue was sampled at 4 times in quadruplicate relating to estimated water contents of 35%, 15%, 5% and 1%. RNA was extracted and RNAseq used to generate transcriptome profiles at each sampling point. Transcriptomes were assembled using the published reference genome sequence and differential gene expression analysed using 3 different programmes, DESeq2, edgeR and limma (with the voom transformation), individually and in combination, deriving Early, Middle and Late stage comparisons. Identified differentially expressed genes were then associated with enriched GO terms using BLAST2GO. For the leaf, up-regulated differentially expressed genes were strongly associated with GO terms only during the Early stage and the majority of GO terms were associated with only down-regulated genes at the Middle or Late stages. For the roots, few differentially expressed genes were identified at either Early or Middle stages. Only one replicate at 1% estimated water content produced high quality data for the root, however, this indicated a high level of differential expression. Again the majority of enriched GO terms were associated with down-regulated genes. The performance of the different analysis programmes and the annotations associated with identified differentially expressed genes is discussed. [ABSTRACT FROM AUTHOR]

A complete randomized design was used to investigate the effect of increasing pasture species on herbage production, chemical composition and utilization under intensive sheep grazing. Four experimental farmlets were established, namely perennial ryegrass (Lolium perenne) only, receiving 163 kg N ha−1 year−1 (PRG); a perennial ryegrass and white clover (Trifolium repens) sward (PRGWC); a six species sward containing two grasses, two legumes and two herbs (6S); and a nine species sward containing three grasses, three legumes and three herbs (9S), each receiving 90 kg N ha−1 year−1. Ewes (12.5 ewes ha−1) and lambs rotationally grazed each farmlet from turnout post‐lambing until housing. Target pre‐grazing herbage mass (above 4 cm) was 1,200 kg dry‐matter (DM) ha−1, Target post‐grazing sward height was 4 cm for all rotations. Herbage samples were collected for DM yield, botanical and chemical composition determination at each grazing. Annual DM production of the 6S, 9S and PRG swards was similar (10.3, 9.9 and 9.9 ± 0.5 t DM ha−1, respectively) despite differences in N application. The 6S sward, however, had greater annual DM production compared to the PRGWC sward (9.1 t DM ha−1, p < 0.05). Herb proportions decreased in the 6S and 9S swards from 2015 to 2016 (p < 0.05) resulting in increased proportions of grass in these swards (p < 0.05). In conclusion, the PRGWC, 6S and 9S swards produced similar annual herbage DM from lower N inputs to PRG swards; however, maintaining the proportions of herbs is a challenge under intensive sheep grazing. [ABSTRACT FROM AUTHOR]

The perennial ryegrass is the species widely used in Europe as forage as well as for creating lawns in urban areas. Unfavourable light conditions in cities are the principal reason of improper growth and functioning of grass communities. The aim of our work was to answer the following questions: what is the adaptive ability of photosynthetic apparatus of perennial ryegrass varieties to long-term reduction of solar radiation and which of the tested varieties has the best properties to be used for grassland establishment under reduced light conditions. A two-factor experiment was conducted with three varieties and three shading variants. Measurements of chlorophyll a fluorescence were provided, and the basic assessed parameters were: minimal fluorescence (F0), maximal fluorescence (Fm), variable fluorescence (Fv) and maximal photosynthetic efficiency of photosystem II (Fv/Fm). Gas exchange was also measured. We explored the differences between the selected varieties in terms of their photosynthetic apparatus adaptation to light conditions. During May, all varieties were characterized by increase in minimal and maximal fluorescence levels under reduced light. The most significant changes were noticed for variety 'Taya'. During following months, a trend of decline in photosynthetic efficiency was observed for this variety. For this variety the most significant changes of CO2 were also noted. The stomatal conductance was not affected by shading. On the basis of our results, we have assumed that each variety is unique in terms of threshold values and demand for light. [ABSTRACT FROM AUTHOR]

Co-expression of diacylglycerol O -acyltransferase (DGAT1) and a lipid droplet-stabilizing protein called Cys-oleosin (collectively 'HME' technology) increases foliar lipid concentrations and plant biomass, which could elevate energy yields from perennial ryegrass (PR, Lolium perenne L.)-based pastures. Quantifying the feasible benefits of HME PR necessitates that herbage growth and energy density are quantified on a ground area basis under regular defoliation. We examined the translation, from spaced pots indoors to field canopies (swards), of the fatty acid (FA), gross energy (GE), and biomass enhancing traits associated with HME technology expression in PR. Under controlled indoor conditions in spaced pots, hemizygous HME seedlings with 32% higher leaf FA content (1.2%DW) than null controls exhibited a faster rate of leaf extension. These effects translated into a stable 0.2–0.5 kJ/gDW increase in herbage GE concentration, and a 6–10% herbage growth rate advantage when HME 'miniswards' were grown under moderate light competition (LAI 7–9) for five defoliation and regrowth cycles (harvests). However, subsequent growth in a dense canopy (LAI>10) eliminated this HME herbage growth advantage. In two field trials in the Midwest United States, hemizygous HME swards exhibited 25–34% (0.8–1%DW) higher end-of-season herbage FA content than null control swards, and 0.2–0.5 kJ/gDW higher end-of-season herbage GE. Herbage growth rates were generally similar for HME and null control swards across both field seasons. This thorough analysis of trait translation shows that the benefits of enhanced FA and GE translate to HME PR canopies grown in the field. The intrinsic growth advantage of HME PR may be diminished in field canopies such that yield benefits are realized only under limited conditions. [ABSTRACT FROM AUTHOR]

Background and Scope Self-incompatibility (SI) in flowering plants ensures the maintenance of genetic diversity by ensuring outbreeding. Different genetic and mechanistic systems of SI among flowering plants suggest either multiple origins of SI or considerable evolutionary diversification. In the grasses, SI is based on two loci, S and Z, which are both polyallelic: an incompatible reaction occurs only if both S and Z alleles are matched in individual pollen with alleles of the pistil on which they alight. Such incompatibility is referred to as gametophytic SI (GSI). The mechanics of grass GSI is poorly understood relative to the well-characterized S-RNase-based single-locus GSI systems (Solanaceae, Rosaceae, Plantaginaceae), or the Papaver recognition system that triggers a calcium-dependent signalling network culminating in programmed cell death. There is every reason to suggest that the grass SI system represents yet another mechanism of SI. S and Z loci have been mapped using isozymes to linkage groups C1 and C2 of the Triticeae consensus maps in Secale, Phalaris and Lolium. Recently, in Lolium perenne, in order to finely map and identify S and Z, more closely spaced markers have been developed based on cDNA and repeat DNA sequences, in part from genomic regions syntenic between the grasses. Several genes tightly linked to the S and Z loci were identified, but so far no convincing candidate has emerged. Research and Progress From subtracted Lolium immature stigma cDNA libraries derived from S and Z genotyped individuals enriched for SI potential component genes, kinase enzyme domains, a calmodulin-dependent kinase and a peptide with several calcium (Ca2+) binding domains were identified. Preliminary findings suggest that Ca2+ signalling and phosphorylation may be involved in Lolium GSI. This is supported by the inhibition of Lolium SI by Ca2+ channel blockers lanthanum (La3+) and verapamil, and by findings of increased phosphorylation activity during an SI response. [ABSTRACT FROM PUBLISHER]

The objective of the present study was to assess perennial ryegrass seasonal herbage accumulation, growth rate (GR), tiller population density (TPD) and weight (TW) at different grazing frequencies and intensities. Treatments consisted of two grazing frequencies (14 and 21 d in the rainy season and 35 and 42 d in the dry and cold seasons) and three grazing intensities: (hard 4-6 cm); medium (6-8 cm) and lax (8-10 cm) in a completely randomized block design with a factorial 2×3 arrangement and three replicates. In the rainy season herbage accumulation was 28 % greater (P<0.05) at 21 d grazing frequency than at 14 d grazing frequency (4,457 vs 3,457 kg DM ha-1). In the cold and dry seasons herbage accumulation at 35 d interval produced 27 % more herbage than at 42 d interval (2.270 vs 1,787 kg DM ha-1). Medium intensity grazing yielded more herbage than both hard and lax in the three seasons. The highest GR was recorded in the rainy season, especially in August at 21 d frequency and medium intensity. The highest TPD (8,042 tillers m-2) was recorded also in August and tended to drop in September. Tiller weight had the greatest influence on herbage yield at 21 d frequency in the rainy season, and TPD increased herbage yield at the beginning of the following rainy season. [ABSTRACT FROM AUTHOR]

• Average bite mass was greater when pasture allowance was greater. • Bite mass was greatest in the first hour of grazing and then declined. • No difference in bite mass was found when cows grazed low and medium pasture mass. Dry matter intake (DMI) of herbage is a product of bite rate and bite mass and is a determinant of the performance of grazing ruminants. This research tested the effect of herbage allowance and herbage mass on average bite mass of individual dairy cows grazing perennial ryegrass herbage (Lolium perenne L.). Two experiments were conducted, one in each of winter (Experiment 1) and spring (Experiment 2). In each experiment, 24 Holstein-Friesian dairy cows grazed individual perennial ryegrass plots over 10 d. In each experiment cows grazed one of six treatments: low or medium herbage mass (1900 or 2200 kg DM.ha−1 in Experiment 1 and 2200 or 3000 kg DM.ha−1 in Experiment 2) combined with either low, medium or high herbage allowance (15, 25 or 40 kg DM.cow−1.d−1 in Experiment 1 and 20, 30 or 40 kg DM.cow−1.d-1 in Experiment 2). Grazing behaviour was measured with jaw movement sensors and DMI was determined by herbage disappearance measured with a rising plate meter daily, and at hourly intervals during the first 4 h of grazing after the morning milking. Average bite mass (g DM.bite−1) per day and per hour was determined as the mass of herbage that had disappeared in each period (g.d−1 or g. h−1) divided by number of prehension bites in that period. The combined data from two experiments was analysed by Linear Mixed Model and it was found there was no effect of herbage mass (P = 0.686) on bite mass per day. However, cows offered high herbage allowance had greater (P < 0.001) bite mass per day (0.62 g DM.bite-1) than cows offered the lowest herbage allowance (0.38 g DM.bite-1) across both experiments. The effect of herbage allowance was similar across both herbage masses. Bite mass per hour was the highest (P < 0.001) in the first hour of grazing in both experiments with average bite mass per hour across two experiments in the first hour of grazing (0.69 g DM.bite−1) greater than in the second (0.40 g DM.bite−1), third (0.35 g DM.bite−1) and fourth (0.32 g DM.bite−1) hours of grazing. We conclude that herbage allowance is a significant factor in determining bite mass and should be included in models aimed at predicting bite mass and hence daily herbage intake of grazing dairy cows. [ABSTRACT FROM AUTHOR]

Perennial ryegrass ( Lolium perenne L.) is one of the most valuable temperate pasture grasses in the world. Understanding seed germination in response to temperature can help determine its optimal seeding times. Germination tests for two cultivars of perennial ryegrass (cv. ‘Turfstar’ and cv. ‘Transtar’) were conducted by applying thirty-six constant and alternating temperature regimes, ranging from 5 to 40°C (16 h night/8 h day). Responses in germination rate to these temperature regimes were then used to construct a quadratic response surface, giving estimated germination rates with confidence intervals at P ≤ 0·05 for both cultivars. Optimum germination rate occurred over a range of regimes: 15/25, 20/25, 20/30 and 25/30°C. Furthermore, a wide range in diurnal alternating temperatures resulted in maximum seed germination rate for cv. ‘Transtar’, while no constant temperature regime supported maximum germination rate for cv. ‘Turfstar’. A temperature-dependent germination rate function for perennial ryegrass was developed which could be used in the future to predict location-specific optimum seeding times when national or regional monthly temperature data are available. [ABSTRACT FROM AUTHOR]

Amplification of 105 Lolium perenne SSR markers was studied in 23 grass species representing seven tribes from three subfamilies of Poaceae. Twelve of the SSR markers are published for the first time. Between 2% and 96% of the SSR markers could be amplified within a given species. A subset of eight SSR markers was evaluated for polymorphism across nine of the 23 grass species. Four to seven of the markers were polymorphic within each species, with an average detection of 2.4 alleles per species. [ABSTRACT FROM AUTHOR]

Plant breeding has developed perennial ryegrass varieties with increased concentrations of water-soluble carbohydrates (WSCs) compared with conventional varieties. Water-soluble carbohydrates are major metabolic and storage components in ryegrass. Therefore, if perennial ryegrass herbage is allowed to grow to greater heights it should contain higher water-soluble carbohydrates concentrations, for example as under rotational grazing rather than continuous grazing by livestock. This study investigated this hypothesis and measured the performance of lambs grazed rotationally and continuously. Replicated plots of the variety AberDart (bred to express high WSC concentrations) or the variety Fennema were grazed by a core group of ten male Cheviot lambs for 10 weeks. Lambs were weighed and replicate forage samples were taken every 7 d. Concentrations of WSC in AberDart herbage were significantly ( P < 0·05), but not substantially, higher than those in Fennema herbage. Rotational grazing did not increase the differential in WSC concentration between the AberDart and Fennema varieties. However, there was a tendency ( P = 0·07) for lambs rotationally grazing the AberDart swards to have a higher final live weight than lambs grazing the Fennema swards. Overall, lamb performance was increased when either perennial ryegrass variety was rotationally rather than continuously grazed ( P < 0·001). [ABSTRACT FROM AUTHOR]

Establishment of seeded 'Zenith' zoysiagrass (Zoysia japonica Stead.) in an existing sward of perennial ryegrass (Lolium perenne L.) is difficult, and chemicals arising from perennial ryegrass leaf and root tissue may contribute to establishment failure. Experiments were done to evaluate zoysiagrass emergence and growth in soil amended with perennial ryegrass leaves or roots, or after irrigation with water in which perennial ryegrass leaves or roots had previously been soaked. Compared to unamended soil, soil amended with perennial ryegrass leaves at 12% and 23% by weight reduced zoysiagrass seedling number 20% and 260%, respectively; root area and mass were reduced 50% when amendments comprised 12% of soil weight. Similar reductions in zoysiagrass seedling emergence and growth were observed in a second soil amendment study, regardless of whether perennial ryegrass was treated with glyphosate or not. Soil mixed with perennial ryegrass leaves, but not roots, at 12% by weight had a high soil conductivity (5.1 dS⋅m-1), which could have contributed to reduced zoysiagrass emergence and growth. More than 50% fewer zoysiagrass seedlings emerged and root mass was up to 65% lower when irrigated with water in which perennial ryegrass leaves or roots at 5, 10, or 20 g⋅L-1 were previously soaked for 48 hours. Zoysiagrass leaf area, and root length and area, were also lower when irrigated with water previously containing perennial ryegrass roots. Perennial ryegrass leaves and roots have the capacity to inhibit emergence and growth of 'Zenith' zoysiagrass seedlings, which could negatively affect stand establishment. [ABSTRACT FROM AUTHOR]

Crown rust resistance is an important selection criterion in ryegrass breeding. The disease, caused by the biotrophic fungus Puccinia coronata, causes yield losses and reduced quality. In this study, we used linkage mapping and QTL analysis to unravel the genomic organization of crown rust resistance in a Lolium perenne population. The progeny of a pair cross between a susceptible and a resistant plant were analysed for crown rust resistance. A linkage map, consisting of 227 loci (AFLP, SSR, RFLP and STS) and spanning 744 cM, was generated using the two-way pseudo-testcross approach from 252 individuals. QTL analysis revealed four genomic regions involved in crown rust resistance. Two QTLs were located on LG1 (LpPc4 and LpPc2) and two on LG2 (LpPc3 and LpPc1). They explain 12.5, 24.9, 5.5 and 2.6% of phenotypic variance, respectively. An STS marker, showing homology to R genes, maps in the proximity of LpPc2. Further research is, however, necessary to check the presence of functional R genes in this region. Synteny at the QTL level between homologous groups of chromosomes within the Gramineae was observed. LG1 and LG2 show homology with group A and B chromosomes of oat on which crown rust-resistance genes have been identified, and with the group 1 chromosomes of the Triticeae, on which leaf rust-resistance genes have been mapped. These results are of major importance for understanding the molecular background of crown rust resistance in ryegrasses. The identified markers linked to crown rust resistance have the potential for use in marker-assisted breeding.Heredity (2005) 95, 348–357. doi:10.1038/sj.hdy.6800729; published online 24 August 2005 [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the reliability of the n-alkane technique for estimating the species composition of Lolium perenne (ryegrass, L) and Festuca arundinacea (tall fescue, F) mixtures. Samples of L and F were collected in May (period 1) and June 2003 (period 2) on mono-specific swards that were maintained at a height of 9 cm. Seven sets of mixtures containing controlled proportions of L and F were then prepared: 1·00:0, 0·80:0·20, 0·60:0·40, 0·50:0·50, 0·40:0·60, 0·20:0·80 and 0:1·00 of L:F, respectively, in the mixture. The proportion of each species in the mixtures was estimated from measured n-alkane concentrations, and then compared with the actual known proportion. Various n-alkane combinations were tested and compared to establish which combination gave the best estimate. Total n-alkane concentrations, and especially C29- and C31-alkane concentrations, were higher in period 1 than in period 2 for both species. The best n-alkane combination varied between periods, as did the effectiveness of C29-alkane in discriminating between L and F. The species composition of the mixtures was satisfactorily estimated for the majority of n-alkane combinations, providing the combination included n-alkanes with contrasting profiles between both species. A systematic overestimation of the proportion of ryegrass was observed for the 0·50:0·50 mixture. [ABSTRACT FROM AUTHOR]

Four perennial ryegrass ( Lolium perenne L.) cultivars were compared for differences in herbage production, nutritive value and herbage intake of dry matter (DM) during the summers of 2002 and 2003. Two paddocks were sown with pure stands of four cultivars in a randomized block design with three replicates. Each plot was subdivided into fourteen subplots (22 m × 6 m) which were grazed by one cow during 24 h. Twelve lactating dairy cows were assigned to one cultivar for a period of 2 weeks in a 4 × 4 Latin square experimental design; the experiment lasted 8 weeks in each year. Sward structure (sward surface height, DM yield, green leaf mass, bulk density and tiller density) and morphological characteristics were measured. The ash, neutral-detergent fibre, acid-detergent lignin, crude protein and water-soluble carbohydrate concentrations, and in vitro digestibility of the herbage were measured. The sward was also examined for infestation by crown rust ( Puccinia coronata f. sp. lolii). Herbage intake of dairy cows was estimated using the n-alkane technique. Cultivar differences for all sward structural characteristics were found except for bulk density and tiller density in 2003. Cultivars differed for proportions of pseudostem, stem (in 2003 only) and dead material. The chemical composition of the herbage was different among cultivars, with the water-soluble carbohydrate concentration showing large variation (>0·35). Cultivars differed in susceptibility to crown rust. Herbage intake differed among cultivars in 2002 (>2 kg DM) but not in 2003. Herbage intake was positively associated with sward height, DM yield and green leaf mass. Canopy morphology did not affect herbage intake. Crown rust affected herbage intake negatively. It was concluded that options for breeders to select for higher intake were limited. High-yielding cultivars and cultivars highly resistant to crown rust were positively related with a high herbage intake. [ABSTRACT FROM AUTHOR]

The symbiotic relationships betweenNeotyphodiumendophytes (Clavicipitacea) and certain cool-season (C3) grasses result in the synthesis of several alkaloids that defend the plant against herbivory. Over a 3 month period we evaluated the effects of temperature on the expression of these alkaloids in tall fescue,Festuca arundinaceaSchreb, and perennial ryegrass,Lolium perenneL. (Poaceae). Response surface regression analysis indicated that month, temperature, and their interaction had an impact on the alkaloid levels in both grasses. We aimed to identify the alkaloids most closely associated with enhanced resistance to the fall armyworm,Spodoptera frugiperdaJE Smith (Lepidoptera: Noctuidae), and clarify the role of temperature in governing the expression of these alkaloids. The dry weights and survival of fall armyworms feeding on endophyte-infected tall fescue or perennial ryegrass were significantly lower than for those feeding on uninfected grass, whereas endophyte infection had no significant influence on survival. For tall fescue, a four-alkaloid model consisting of a plant alkaloid, perloline, and the fungal alkaloids ergonovine chanoclavine, and ergocryptine, explained 47% of the variation in fall armyworm dry weight, whereas a three-alkaloid model consisting of the plant alkaloid perloline methyl ether and the fungal alkaloids ergonovine and ergocryptine explained 70% of the variation in fall armyworm dry weight on perennial ryegrass. Although temperature had a significant influence on overall alkaloid expression in both grasses, the influence of temperature on individual alkaloids varied over time. The levels of those alkaloids most closely linked to armyworm performance increased linearly or curvilinearly with increasing temperature during the last 2 months of the study. We conclude that the growth temperature of grasses can influence the performance of fall armyworm, and that this effect may be mediated through a set of plant- and endophyte-related alkaloids. [ABSTRACT FROM AUTHOR]

An object-oriented simulation model was developed to integrate detailed analyses of perennial ryegrass (Lolium perenne) plant part dimensions, and their mass, cell wall content (CWC) and cell wall digestibility (CWD). The model was validated against data from two field experiments, carried out in The Netherlands (52°N) and Norway (67°N). In the experiments, the effects of temperature × daylength interactions on development, growth and digestibility were determined. Three cultivars differing in heading date were used, and undisturbed growth and regrowth after early (only in The Netherlands) and late cutting were studied. The sensitivity of the model was tested for changes in parameters determining morphological development.A grass plant was modelled as an aggregation of shoot objects. A shoot is an aggregation of phytomers, plus an inflorescence in the reproductive development stage. A phytomer consists of a leaf blade, a leaf sheath, a stem internode and a root. Each phytomer has an axillary bud, which can develop into a new shoot.Morphological development, organic matter (OM) growth and composition were simulated well by the model. Only for regrowing crops in The Netherlands CWC was lower and CWD was higher in the simulations than observed in the field, whereas the differences increased when stem development was more advanced at the moment of cutting. This was attributed to residual stems in the stubble after cutting due to difficulties with machine cutting of lodged crops on the experimental plots. The model can be considered as sufficiently accurate to simulate OM yield and composition of grass cultivars differing in heading date and growing under strongly contrasting temperature and daylength conditions. When the leaf appearance rate, width or length of the leaf blade were increased in the sensitivity analysis, OM yield enhanced, but composition and digestibility of the reproductive grass crops were not systematically affected. [Copyright &y& Elsevier]

Quantitative trait loci (QTLs) for a number of agronomically important traits of perennial ryegrass (Lolium perenne L.) were identified by means of a reference molecular marker-based genetic map. Replicated phenotypic data was obtained for a number of field-assessed morphological and developmental traits as well as the winter hardiness-associated characters of winter survival and electrical conductivity. Marker-trait association analysis was performed by a number of methods, and a high degree of congruence was observed between the respective results. QTLs were detected for morphological traits such as plant height, tiller size, leaf length, leaf width, fresh weight at harvest, plant type, spikelet number per spike and spike length, as well as the developmental traits of heading date and degree of aftermath heading. A number of traits were significantly correlated, and coincident QTL locations were identified. No significant QTLs for winter survival in the field were identified. However, a QTL for electrical conductivity corresponding to frost tolerance was located close to a heading date QTL in a region that may show conserved synteny with chromosomal regions associated with both winter hardiness and flowering time variation in cereals. The QTL analysis of multiple phenotypic traits provides the basis for marker assisted selection (MAS) of important agronomic characters, allowing genetic improvement of yield, quality and adaptation in perennial ryegrass breeding. [ABSTRACT FROM AUTHOR]

Extension of the vegetative growth phase through delay of flowering is an important goal in today’s breeding programs of both forage and turf grasses. In forage grasses, the stem and inflorescence production comprise a significant reduction in the digestibility, nutritional value and productivity of the crop, and in turf grasses the stems that start to emerge during the growth season suppress the formation of new shoots and affect the quality, density and persistence of the sward. We have tested the potential of the strong floral repressor LpTFL1 from perennial ryegrass (Lolium perenne L.) to manipulate the transition to flowering in red fescue (Festuca rubra L.), a cool-season turf grass. Expression of LpTFL1 from the constitutive maize ubiquitin promoter represses flowering in red fescue, and the flowering repression phenotype correlates well with the level of LpTFL expression. Transgenic lines showing low to intermediate expression of LpTFL1 flowered approximately two weeks later than the controls, and transgenic lines showing very high LpTFL1 expression levels still remained non-flowering after exposure to natural vernalization conditions (Danish winter) in two successive years. There were no other phenotypic effects associated with the LpTFL transgene expression during vegetative growth. However, there was a tendency towards an LpTFL1-mediated reduction in stem length among the flowering lines. Expression of a truncated LpTFL, caused by transgene rearrangements during the transformation, lead to increased flowering and stem production and a decrease in panicle size. This is to our knowledge the first report on full inhibition of floral development in a commercially important grass species. [ABSTRACT FROM AUTHOR]

Grass-dominated vegetation covers large areas of the Dutch river floodplains. Remotely sensed data on the conditions under which this vegetation grows may yield information about the degree of soil contamination. This paper explores the relationship between grassland canopy reflectance and zinc (Zn) contamination in the soil under semi-field conditions. A field radiometer was used to record reflectance spectra of perennial ryegrass ( Lolium perenne ) in an experimental field with Zn concentrations in the soil ranging from 32 to 1800 mg kg -1 . Several spectral vegetation indices (VIs) and a multivariate approach using partial least squares (PLS) regression were investigated to evaluate their potential use in estimating Zn contamination levels. Compared to the best PLS model (RMSEP=181.4 mg kg -1 ), the narrow band vegetation index MSAVI2mm performed better (RMSEP=162.9 mg kg -1 ). Both MSAVI2mm and PLS gave a high user accuracy for the strongly contaminated soil class (100% and 91%, respectively), while the total accuracy was satisfactory (60% and 55%, respectively). Results from this feasibility study indicate the potential of using remote sensing techniques for the classification of contaminated areas in river floodplains. But as the results from this study may be both resolution- and location-dependent, research on field and image scale is now required to test the established relations and to assess their susceptibility to seasonal influences, species heterogeneity, and increased levels of spectral noise. [ABSTRACT FROM AUTHOR]

Wintering ability in the field and resistance to different winter-stress factors under controlled environmental conditions were studied in a full-sib family of perennial ryegrass (Lolium perenne L.). Significant variation in tolerance to freezing and ice encasement, resistance to pink snow mould (Microdochium nivale) and also in winter survival and spring growth were found between the different genotypes. No strong correlations were found between the resistances to the different stress factors. These results indicate that resistance to different winter-stress factors is controlled by separate genes in perennial ryegrass. A low but significant positive correlation was found between spring growth of plants in the field after the first winter and both freezing tolerance and M. nivale resistance measured in controlled environments. Cold hardening seemed to influence freezing tolerance and M. nivale resistance differently in the different genotypes, since no distinct correlation in tolerance to freezing or resistance to M. nivale was found between unhardened and hardened plants. Tolerance or resistance to most of the winter stress factors measured was positively correlated with plant size. [ABSTRACT FROM AUTHOR]

The characters causing low seed-setting rates in induced tetraploid Lolium perenne L. were investigated. The objective of this study was to determine whether these characters could be used as criteria in the selection of regular meiosis and high seed-setting plants. The seeds of C 1 and C 2 generations of artificially obtained tetraploid perennial ryegrass were used. Cytological studies were done on the root tips and spike samples. A significant positive correlation was found between the frequency of cells showing regular anaphase I and high seed-setting rates. As a result, it was decided that this normal separation in anaphase I could be used as a selection criterion for seed set. The highly significant negative correlation that was found between the number of micronuclei and seed setting showed that this character could also be used as a selection criterion when a large population is under consideration. It was necessary to isolate aneuploids from euploid plants to increase fertility. [ABSTRACT FROM AUTHOR]

In a field experiment nitrogen (N) fertilizer was applied to small plots of perennial ryegrass (Lolium perenne) at rates equivalent to 0, 200, 400 and 600 kg N/ha/yr at each of two levels of potassium (K) 0 and 200 kg K/ha/yr. Plots were cut at 6-week intervals during 1977-79 and dry matter yield was determined. Water-soluble carbohydrate and N content of the foliage were measured at three harvests in 1977. The incidence and severity of Drechslera spp. were assessed at and between harvests; attack by Puccinia coronata was assessed each autumn. Most foliar damage was caused by Drechslera spp. This was increased by N application which also altered the relative proportions of the Drechslera spp. present. K application had no apparent effect on disease incidence. Puccinia coronata was more prevalent on older leaves and on one occasion its incidence was increased by N application. [ABSTRACT FROM AUTHOR]

Changes in carbohydrate content and composition of ryegrass (Lolium perenne L.) cv. Réveille field-grown in Normandy were investigated from May 1987 to May 1988. During the winter period, the concentrations of high DP (degree of polymerization) fructan were the lowest whilst those of ethanol-soluble carbohydrates were the highest. Ethanol-soluble carbohydrates also accounted for most of the non-structural carbohydrates of four cultivars of Lolium perenne field-grown in central France in January 1989. The accumulation of osmotically active carbohydrates during winter leads only to a small depression of freezing point and consequently, these sugars cannot be considered as efficient cryoprotectants in ryegrass. [ABSTRACT FROM AUTHOR]

To gain a deeper understanding of the mechanisms underlying associations between allozyme genotypes and rates of respiration in Lolium perenne, Vmax, Km, and rates of glucose flux through glycolysis and the pentose phosphate pathway were estimated for the three genotypes of the 6pgd locus. Km, Vmax, and Vmax/Km differed significantly among genotypes. Values of Km for the 11, 12, and 22 genotypes were 0.29, 0.25, 0.13, while the values of Vmax/Km for the 11, 12, and 22 genotypes were 3.79, 3.85, 6.70. Flux through the pentose shunt did not differ among genotypes at 20°C, but at 35°C the rates of flux for the 11, 12, and 22 genotypes were 0.15, 0.25 and 0.42, respectively. Thus, the 6PGD allozyme genotypes differ markedly in both enzyme kinetic characteristics and in flux through a metabolic pathway. These associations reveal potentially causal relationships between allozyme genotypes and rates of respiration. [ABSTRACT FROM AUTHOR]

Improving rust resistance is one of the main goals in our breeding programme with perennial ryegrasses. We have studied the behaviour of our breeding material over several years in several locations under natural and artificial infection conditions. The narrow sense heritability of crown rust resistance is fairly high (0.46), providing scope for improving resistance, but this optimism is reduced by the negative correlation with yield. The most resistant material yielded 4% less than the most susceptible material. No decline in digestibility is expected when improving the disease resistance. The incidence of crown rust is very variable between years, locations and between spontaneous and artificial infections, creating constraints in selection. Observations for several years and at several locations appear to be the best way to improve rust resistance in perennial ryegrass. [ABSTRACT FROM AUTHOR]

The in parameters, variances, covariances and heritabilities, caused by the Bulmer effect have been predicted for an artificial breeding population of perennial ryegrass using recursion formulae. This enabled anticipation of the decrease in the expected response to multitrait index selection, using two different sets of economic weights. This theoretical decrease in selection efficiency was found to be quite substantial; it is approximately halved after 4 cycles of individual recurrent selection with a fairly high selection intensity of 5 %. However the synthetic population is improved for 4 out of 5 agronomic traits and could theoretically reach quite a high level of performance after 5 cycles. The choice of economic weights has relatively little influence on the expected genetic progress of each trait. [ABSTRACT FROM AUTHOR]

The objective of the study was to determine the effect of selection for large root dimension on root and shoot characteristics of an Italian variety of Lolium perenne L. (cv. ‘Vejo’). Two cycles of recurrent restricted phenotypic selection (RRPS) were carried out in 1983 and 1984 at Perugia (Italy). In each cycle, 20 out of 1,500 plants were selected and intercrossed under isolation. In 1985, 120 plants from ‘Vejo selected’ and an equal number of plants from ‘Vejo’ initial seed-lot were grown hydroponically for 92 days; at the end of the experiment, the plants were measured for their number of leaves and stems, leaf length, length of the longest root, root volume and shoot and root dry weight. Sufficient genetic variability existed among plants of cv. ‘Vejo’ to allow highly significant responses to selection for root dimension (+ 2i % in root length, +39 % in root volume, 4-67 % in root dry weight and + 3 1 % in root: shoot dry weight ratio). Furthermore, two cycles of RRPS for root dimension did not show negative responses of the aboveground parts of the plant. [ABSTRACT FROM AUTHOR]

The investigation was carried out to obtain double haploid homozygous lines of Lolium. Lolium multiflorum ssp. gaudini cv. 'Liwelo', 44 clones and five different cultivars (cv.) of L. perenne were tested with regard to their anther culture response on a solid medium. Callus production and plant regeneration of the different genotypes were investigated. Within L. m. ssp. gaudini green plants have been obtained. In L. perenne significant genotypical differences in the in vitro reaction could be demonstrated. A high-responding genotype was selected which produced a maximum of 20 % green plants. A variety × temperature interaction was found for the L. perenne varieties 'Premier' and 'Barlenna'. The production of 34 green plants out of eight clones enables a first analysis to be made of the inheritance of Barley Yellow Dwarf Virus resistance in L. perenne. [ABSTRACT FROM AUTHOR]

From 22 genotypes, selfed (S1) and testcross progenies were investigated. The latter were generated by i) polycross (PX) and ii) 2 topcrosses (TC) using cms-inbred lines as a tester. Progenies were tested for annual dry matter yield in 3 successive years, the 3-year average was 76.7 dt/ha for S2 and 76.9, 80.1 and 74.5 for PX, TC 1 and TC 2, respectively. Genetic variance was highest for S11 (20.42), while the average of the 3 testcrosses was 12.22. However, the genotype-year interaction variance of S: Was 52.21, being 2--3 times greater than for the 2 topcrosses. PX progenies were the most stable across years. Predicted response to selection was highest for S1 (10.4 %). Genetic correlation (rg) between S1 and the testcrosses was highest with TC 2 (rg = 0.593+ +). [ABSTRACT FROM AUTHOR]

From 28 genotypes, half-sib families were generated by polycross (PX) and 2 topcrosses (TC). TC-testers were partially inbred cms-lines. Progenies were tested for annual dry matter yield in 3 successive years. The three year average was 80.7, 76.6 and 74.0 dt/ha for TC 1, PX and TC 2, respectively. TC 1 had the highest yielding families and the largest mean in all years. TC 2 revealed the largest range among its families. Genetic variance was highest for TC 2 with 14.02, followed by TC 1 and PX with 12.05 and 10.92. However, genotype × year interaction variance was about 2 and 4 times greater for TC 1 and TC 2 as compared to PX. Genetic correlation between testcross progenies was tightest for PX vs. TC 1 (rg = 0.644++ ), while between the two TC's only rg = 0.307+ was observed. Predicted response to selection yielded very similar results for all test-crosses. [ABSTRACT FROM AUTHOR]

A Triple Test Cross and basic generations (i.e. inbred parents, F1's, F2's and backcrosses) have been used to investigate the generics of dry matter yield in a population of Lolium perenne. Two trial designs, short, individual plant drills and larger sown plots were used at each of two sites iii the U.K., at Aberystwyth and Birmingham. The families studied correspond to those raised as spaced plants and reported in the first paper in this series. In contrast to the spaced plants trial, the drill trial resulted in considerable epistasis as well as additivity and dominance variation whilst the plot trial failed to identify any significant genetic variation. There "as considerable G × E interaction over sites and harvests, particularly in the amount of dominance. The latter showed a clear linear relationship with mean per- formance at both sites, the dominance ratio being higher in the poorest environments. This is largely due to the additive variance decreasing in the poor environments rather than the dominance being higher. The implications of these results to grass breeding are discussed. [ABSTRACT FROM AUTHOR]

A diallel crossing programme amongst four contrasting white clover varieties was used to generate material for studying the interrelationships amongst those characters which affect the productivity of white clover-perennial ryegrass mixtures under a cutting-only management regime. Such a regime favoured clover growth. All the clover characters exhibited strong positive correlations with mixture yield. However, this combination of clover characters did nor promote growth of the grass companion. For this a low growing variety with a dense stolon network appeared preferable. Path analysis indicated that differences existed between the two companion grass varieties used for this experiment in their effects upon clover characters. [ABSTRACT FROM AUTHOR]

Components of seed yield were estimated for each set of 100 plants derived from six varieties of Lolium perenne. Significant differences between the varieties were found for all components of seed yield, but the range was broader within each variety. An indirect selection of seed yield using the character seeds per spike produced a selection response similar to that obtained by direct selection on high seed yield per plant. A direct and indirect selection of characters estimated in small, drilled plots of topcross off- springs (F1) was less successful than the selection based on the single plants. Spearman rank correlation coefficients between the single plants and their offsprings did not show significant agreement for seed yield. But altogether the results indicated that the increase of seed yield/area was about 6 % when 10 % of the best plants were selected. [ABSTRACT FROM AUTHOR]

Increasing the rate of genetic gain for dry matter (DM) yield in perennial ryegrass (Lolium perenne L.), which is a key source of nutrition for ruminants in temperate environments, is an important goal for breeders. Genomic selection (GS) is a strategy used to improve genetic gain by using molecular marker information to predict breeding values in selection candidates. An empirical assessment of GS for herbage accumulation (HA; proxy for DM yield) and days-to-heading (DTH) was completed by using existing genomic prediction models to conduct one cycle of divergent GS in four selection populations (Pop I G1 and G3; Pop III G1 and G3), for each trait. G1 populations were the offspring of the training set and G3 populations were two generations further on from that. The HA of the High GEBV selection group (SG) progenies, averaged across all four populations, was 28% higher (p < 0.05) than Low GEBV SGs when assessed in the target environment, while it did not differ significantly in a second environment. Divergence was greater in Pop I (43%–65%) than Pop III (10%–16%) and the selection response was higher in G1 than in G3. Divergent GS for DTH also produced significant (p < 0.05) differences between High and Low GEBV SGs in G1 populations (+6.3 to 9.1 days; 31%–61%) and smaller, non-significant (p > 0.05) responses in G3. This study shows that genomic prediction models, trained from a small, composite reference set, can be used to improve traits with contrasting genetic architectures in perennial ryegrass. The results highlight the importance of target environment selection for training models, as well as the influence of relatedness between the training set and selection populations. [ABSTRACT FROM AUTHOR]

To predict any genetic response to selection, two breeding populations of perennial ryegrass, consisting of half-sib families, were evaluated as spaced plants from 1987 to 1989 for several agronomical traits. In each population, the best plants selected through a multitrait Smith and Hazel's index were planted in a polycross to produce the second generation half-sib families. Both generations were evaluated together from 1991 to 1993 as spaced plants. The difference between generations was the observed genetic response, which was compared to that predicted. Rust tolerance, aftermath heading and persistence were significantly improved in both populations. In trial plots used to assess the yield, no effect of mass selection was noticed. Thus it is concluded that mass selection failed to increase productivity but produced some improvements in disease tolerance and aftermath heading. [ABSTRACT FROM AUTHOR]

Simple Summary: Increasing soluble sugars in pasture species can lead to an improved nutrient use efficiency in the rumen and a greater digestibility of forage, which in turn might increase pasture intake. However, this improvement in nutritional value must not be at the expense of pasture productivity; the amount of nutrients harvested is a relevant factor in ruminant grazing systems' efficiency. Therefore, we tested four different cultivars of perennial ryegrass (two selected for greater soluble sugar content and two standard cultivars) submitted to two contrasting managements (one aimed at improving sugar content and one with the opposite intended effect) for their effects on pasture productivity (by cutting herbage every time the plots reached the target number of leaves per tiller, i.e., two or three) and the grazing preference of dairy cows (six cows grazed for up to 5 hours, in an experimental area with three plots for each of the eight treatments) in spring, summer and autumn. We found that high sugar grasses had lower annual dry matter productivity and no preference was shown by cows, although the agronomic management aimed at reducing sugar concentration enhanced crude protein concentration and increased the herbage harvested (greater preference) in the three seasons, and the time spent grazing in autumn. The objective of this study was to evaluate the pasture performance of different cultivars of perennial ryegrass, two "high sugar" and two standard cultivars, under two contrasting agronomic managements (aimed at either decreasing or increasing water soluble carbohydrates concentration), and their effects on the grazing preference of dairy cows. Eight treatments arising from the factorial combination of four cultivars and two managements were randomly applied to 31-m2 plots in three blocks. Pasture dry matter production and growth rate were measured for one year. Three grazing assessments were performed to establish the grazing preferences of six dairy cows in spring, summer and autumn. High sugar cultivars produced less dry matter per hectare than the standard cultivars. Cows consumed more grass and harvested a greater proportion of the pasture under the agronomic management aimed at decreasing sugar concentration, i.e., with a greater nitrogen fertilization rate and under a more frequent defoliation regime, which could be explained by the greater crude protein concentration achieved under this management. The results suggest that the genetic selection for greater levels of sugars was at the expense of herbage yield, and that cows preferred to graze herbage with a greater crude protein level instead of a greater sugar concentration. [ABSTRACT FROM AUTHOR]

Forage grass production is an important component of profitable dairying along the Pacific Northwest coast. Neutral detergent fiber digestibility (NDFD) is increasingly being used in ration formulation and forage benchmarking. However, data on differences in NDFD between and within cool-season grass species is limited. Therefore, the objective of this study was to determine if NDFD differs between and within species. In experiment 1, 15 cool-season grass varieties were replicated 3 times each in 6 m2 randomized field plots. Included were 5 varieties each of perennial ryegrass (Lolium perenne), orchardgrass (Dactylis glomerata), and tall fescue (Lolium arundinaceum). In experiment 2, three diploid and three tetraploid cool-season ryegrass varieties (Lolium perenne) were replicated 3 times each in 6 m2 randomized field plots. Plots were mechanically harvested six times at approximately 28 d intervals beginning in March. Forty eight-hour in vitro neutral detergent fiber (NDF) digestibility was determined using 0.3 g of sample in F57 bags in a DaisyII Incubator (Ankom Technology, Fairport, NY). In experiment 1, yield (2124±79 kg DM/ha/cutting) was similar across species. Neutral detergent fiber was less for ryegrass compared to orchardgrass (47.1 vs 48.5±0.4%; P < 0.01), but similar to both of these grasses was tall fescue (48.0%). Neutral detergent fiber digestibility was greater for ryegrass compared to orchardgrass and tall fescue (80.4 vs 77.5±0.6% of NDF; P < 0.01). Digestible NDF did not differ and was 37.4±0.3% of DM or 799±32 kg/ha/cutting. Neutral detergent fiber increased (linear; P < 0.01) and NDFD decreased (quadratic, cubic; P < 0.05) as the growing season progressed. In experiment 2, yield (2220±110 kg DM/ha/cutting), NDF (47.2±0.5%), NDFD (80.7±0.5%), and digestible NDF (38±0.4% of DM and 851±47 kg DM/ha/cutting) were similar for diploid and tetraploid ryegrasses. These results indicate species, when managed intensively, has little effect on yield and digestibility. [ABSTRACT FROM AUTHOR]