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The objective of this study was to quantify the farm gate nitrogen (N) offset potential of perennial ryegrass (Lolium perenne L.; PRG) white clover (Trifolium repens L.; WC) swards by comparing the herbage and milk production from dairy farmlets that were simulations of full farming systems. A study was established where 120 cows were randomly assigned to 4 farmlets of 10.9 ha (stocking rate: 2.75 cow/ha), composed of 20 paddocks each. Cows were fed 526 kg of DM of concentrate on average each year. The 4 grazing treatments were PRG-only at 150 or 250 kg of N/ha and PRG-WC at 150 or 250 kg of N/ha. Cows remained in their treatment group for an entire grazing season and were re-randomized as they calved across treatments each year. As cows calved in the spring as standard practice in Ireland, they were rotationally grazed from early February both day and night (weather permitting) to mid-November, to a target postgrazing sward height of 4.0 cm. Mean sward WC content was 18.1% and 15.4% for the 150 and 250 kg of N/ha PRG-WC treatments, respectively over the 3-yr period. When WC was included, lowering the N rate did not reduce pregrazing yield, pregrazing height, or herbage removed, but those factors decreased significantly when WC was absent. Total annual herbage DM production was 13,771, 15,242, 14,721, and 15,667 kg of DM/ha for PRG-only swards receiving 150 or 250 kg of N/ha and PRG-WC swards receiving 150 or 250 kg of N/ha, respectively. In addition, when WC was present, compressed postgrazing sward heights were lower (4.10 vs. 4.21 cm) and herbage allowance (approximately 17 kg/cow feed allocation per cow per day) higher than the high-N control (+ 0.7 kg of DM/cow per day). There was a significant increase in milk production, both per cow and per hectare, when WC was included in PRG swards. Over the 3-yr study, cows grazing PRG-WC had greater milk (+304 kg) and milk solids (+31 kg of fat + protein) yields than cows grazing PRG-only swards. This significant increase in milk production suggests that the inclusion of WC in grazing systems can be effectively used to increase milk production per cow and per hectare and help offset nitrogen use. This result shows the potential to increase farm gate N use efficiency and reduce the N surplus compared with PRG-dominant sward grazing systems receiving 250 kg of N/ha, without negatively affecting milk solids yield or herbage production, thus increasing farm profit by €478/ha. [ABSTRACT FROM AUTHOR]

Precise information about carbohydrates and proteins in relation to their utilization in the rumen is useful for the breeding purposes of perennial ryegrass cultivars used for animal nutrition. The objective of the current study was to evaluate 20 diploid perennial ryegrass accessions from the intermediary heading stage. The ruminal kinetics of different carbohydrate and protein fractions of grasses and legumes are important for forage breeding programs. The Cornell Net Carbohydrate and Protein System (CNCPS) was used to provide such information. Accession-based variation can be observed after considering dynamic degradation processes. Variation among the 20 accessions was observed. Ruminally digested (RDC) and undigested (UDC) carbohydrate and ruminally degraded (RDP) and undegraded (UDP) protein contents, total carbohydrate and total protein contents, and carbohydrate and protein fractions for the first cut and annual averages show significant differences. Although the variation was smaller for the protein fractions, the calculated usable protein content (uCP, sum of UDP and amount of synthesized microbial protein in the rumen) in the small intestine is mainly influenced by decreasing the neutral detergent fiber (NDF) and increasing the sugar content among cultivars. Carbohydrate and protein fractionation is suitable for characterizing perennial grass accessions as it uses parameters relevant to ruminant nutrition, allowing a step forward in forage plant breeding for forage quality. To conclude, using parameters related to ruminal degradation kinetics should favor the selection of accessions with higher amounts of ruminally digested carbohydrates (RDC). The selection of accessions based on protein quality (proportion of UDP) is less favorable for achieving a higher usable protein content. [ABSTRACT FROM AUTHOR]

Epichloë festucae uses a siderophore‐mediated system to acquire iron, which is important to maintain endophyte–grass symbioses. Here we investigate the roles of the alternative iron acquisition system, reductive iron assimilation (RIA), via disruption of the fetC gene, which encodes a multicopper ferroxidase, either alone (i.e., ΔfetC) or in combination with disruption of the gene sidA, which encodes a siderophore biosynthesis enzyme (i.e., ΔfetC/ΔsidA). The phenotypic characteristics of these mutants were compared to ΔsidA and wild‐type (WT) strains during growth under axenic culture conditions (in culture) and in symbiosis with the host grass, perennial ryegrass (in planta). Under iron deficiency, the colony growth rate of ΔfetC was slightly slower than that of WT, while the growth of ΔsidA and ΔfetC/ΔsidA mutants was severely suppressed. Siderophore analyses indicated that ΔfetC mutants hyperaccumulate ferriepichloënin A (FEA) at low iron concentrations and ferricrocin and FEA at higher iron concentrations. When compared to WT, all mutant strains displayed hyperbranching hyphal structures and a reduced ratio of Epichloë DNA to total DNA in planta. Furthermore, host colonization and vertical transmission through infection of the host seed were significantly reduced in the ΔfetC/ΔsidA mutants, confirming that high‐affinity iron uptake is a critical process for Epichloë transmission. Thus, RIA and siderophore iron uptake are complementary systems required for the maintenance of iron metabolism, fungal growth, and symbiosis between E. festucae and perennial ryegrass. [ABSTRACT FROM AUTHOR]

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

Perennial ryegrass (Lolium perenne L.) is a commonly grown pasture species in temperate agriculture, mainly serving as a primary energy source for dairy cows. However, its limited persistence often leads to missed production potential and early resowing, especially in countries that experience summer drought, e.g., Australia and New Zealand. Therefore, understanding the factors influencing perennial ryegrass pasture persistence is crucial for sustainable land management and climate resilience in pasture-based animal production systems. Significant gaps in knowledge exist regarding the factors influencing pasture persistence, as the number of conducted studies in this area remains limited. This study aimed to investigate the factors influencing the expression of persistence in perennial ryegrass populations using airborne and ground-based sensors. A field experiment was conducted in the southwest region of Victoria, Australia, involving ten commercial perennial ryegrass cultivar–endophyte combinations in two different populations. Persistence was evaluated using sensor-based and conventional pasture measurements over two consecutive autumns. The results revealed significant fixed effects of cultivar, endophyte, and environment and their interactions on persistence traits of perennial ryegrass. Cultivars Alto, Samson, and One50 exhibited high levels of persistence when infected with novel endophyte strains. Furthermore, prolonged environmental stresses were found to drive directional selection within pasture populations. The findings emphasise the importance of selecting appropriate cultivar–endophyte combinations and early detection of signs of poor persistence to optimise sward longevity and financial returns from pasture-based animal production systems. This study fills a knowledge gap regarding the factors influencing pasture persistence and provides valuable insights for sustainable pasture management strategies. [ABSTRACT FROM AUTHOR]

Perennial ryegrass is an important turf and forage grass in temperate regions worldwide. Limited genetic gains have been made with current breeding strategies compared with other grass crops, such as rice and maize, which benefit from Filial 1 (F1) hybrid breeding. One of the largest constraints on hybrid breeding in ryegrass is self‐incompatibility preventing inbreeding, as homozygous parental lines are required to develop hybrids with maximal hybrid vigour. Obligate outcrossing in ryegrass has resulted in cultivars with high levels of heterozygosity, lacking trait uniformity across the population. A naturally occurring self‐fertile (SF) locus that overcomes the self‐incompatibility system has been identified in a European perennial ryegrass population. This study crossed the SF locus into an elite cultivar, producing a self‐compatible population that was inbred for several generations. Genotyping‐by‐sequencing (GBS) was used to assess the population structure and degree of inbreeding in the self‐compatible population. Phenotypic analysis indicated that increased homozygosity did not necessarily affect growth and performance. This study concludes that self‐compatible ryegrass is a promising tool for hybrid breeding and agronomic improvement of perennial ryegrass. [ABSTRACT FROM AUTHOR]

Background: Tall fescue (TF) and tall wheatgrass (TW) are the main temperate perennial grasses used for livestock grazing in the Pampas region of Argentina. In this region, pastures based on these grasses show low tiller density and the presence of bare soil in winter. Methods: An experiment was performed in pots kept outdoors. Plants of TF and TW were cut every 550°C day and 700°C day, respectively. In each species, reproductive tillers were removed at different times: (i) at each cut, (ii) when they reached the flag leaf stage, or (iii) when they reached full bloom. Tiller appearance, tiller death, and type of bud (basal or axillary) of the tillers present were determined. Results: Tiller appearance decreased from July to April. Minimum values were 0.2 and 1.1 tillers 100 tillers−1 day−1 in TF and TW, respectively. In TF, tiller death began in September–October and increased from 0.2 to 0.8 tillers 100 tillers−1 day−1 in March–April. In TW, tiller death began in October–November and increased from 0.6 to 0.8–1.0 tillers 100 tillers−1 day−1 from February to April. Conclusions: Defoliation of reproductive tillers affected the tiller density of TF plants in spring and in the following fall. In TW, the treatments did not modify the tiller density of the plants. [ABSTRACT FROM AUTHOR]

Fibrous forage and biomass crops such as grass and maize are used at large scale as feed for ruminants and feedstock for biogas production. These crops are typically harvested by chopping them in small particles which are light and suitable for partial pneumatic conveying, where the particle trajectory is determined by their aerodynamic properties. While the aerodynamic properties of many grains have been studied, no reports were found for perennial ryegrass. Chopped ryegrass samples of leaf blades and stems were collected in the fields. After imaging the fresh harvested particles to quantify their size and surface area, their terminal velocity was measured with the fluidised-bed method. The relationship between the mass, projected area and moisture content of the stems and blades with their terminal velocities were modelled. In line with theory, mass and moisture content was positively correlated with terminal velocity, while projected area was negatively correlated with it. Smaller terminal velocities were observed for the blades (1.75 m s−1) compared to the stems (4.44 m s−1). The drag coefficients of grass particles were calculated, and for blades it was negatively correlated with the particle Reynold's number lying within Newton's regime (103 < Re < 3 × 105), whilst no significant correlation was found for stems. The average drag coefficient of blades (0.75) was larger than stems (0.54). No significant effect (p-value <0.01) of moisture content on the drag coefficient of grass particles was observed. This confirms that the drag coefficient is a shape parameter, related to formation of airstreams around the particle. • Aerodynamic properties of ryegrass were quantified in a wind tunnel. • The terminal velocity of grass blades was 61% smaller than that of stems. • Terminal velocities can be predicted from mass, area and moisture content (R2 = 0.77). • Grass particles' drag coefficient was calculated and compared to similar materials. • The drag coefficient of grass blades was 39% larger than that of stems. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the effects of substituting silage of chopped grass with pulp silage of grass fractionated once or twice in a biorefinery using a screw press on fiber kinetics, protein value, and production of CH 4 in dairy cows. Six lactating multiparous Holstein cows in mid-lactation (176 ± 93 d in milk), cannulated in the rumen, duodenum, and ileum, were used in an incomplete 6 × 4 Latin square design with a 2 × 3 factorial arrangement of treatments. Perennial ryegrass was harvested in third regrowth from the same field at early and late developmental stage (35 and 44 d of regrowth, respectively) and subjected to 1 of 3 types of processing within each developmental stage. Grass was either harvested for normal silage making (mowed, wilted, chopped, and ensiled), or harvested fresh and fractionated using a screw press. Half of the pulp from the first fractionation was ensiled, whereas the other half of the pulp was rehydrated, fractionated a second time, and pulp hereof was ensiled. The grass and pulp silages were used with concentrates (65:35 forage to concentrate ratio) to make total mixed rations (TMR) based on either silage of chopped grass (GS), pulp silage of grass fractionated once (1×P), or pulp silage of grass fractionated twice (2×P), harvested either at early (E) or late (L) developmental stage resulting in 6 different TMR treatments (EGS, E1×P, E2×P, LGS, L1×P, L2×P). The TMR were fed for ad libitum intake and samples of intestinal digesta and feces were collected for determination of digestibility. The effect of processing on ash-free neutral detergent fiber (aNDFom) concentration in silages depended on developmental stage, but showed that within each developmental stage, pulp silage of grass fractionated twice had higher aNDFom concentration than pulp silage of grass fractionated once and silage of chopped grass. The 2×P resulted in lower (14.9 ± 0.55 vs. 17.5 ± 0.54 kg/d) dry matter intake (DMI) compared with GS. The effects of processing and developmental stage interacted such that apparent total-tract aNDFom digestibility was higher (784 ± 13 vs. 715 ± 13 g/kg) for L2×P compared with LGS, whereas no difference was found between E2×P and EGS. Moreover, the protein value was higher (106 ± 5 vs. 92 ± 5 g AA digested in the small intestine/kg of DMI) for 2×P compared with GS. Unexpectedly, processing had no effect on fractional rate of digestion of digestible aNDFom or CH 4 yield (L/kg of DMI), whereas feeding forages harvested at early compared with late developmental stage resulted in lower CH 4 yield. Feeding pulp silage of grass fractionated once generally yielded results intermediate to cows fed silage of chopped grass and pulp silage of grass fractionated twice. This study showed that pulp silage of fractionated grass could serve as feed for dairy cows because the fiber digestibility and protein value improved, but further research investigating effects of physical processing of forage on fiber kinetics is required. [ABSTRACT FROM AUTHOR]

In summer 2018, brown stripe symptoms were observed on leaf blades of perennial ryegrass (Lolium perenne L.) used as a turfgrass in an athletic field in Saitama Prefecture, Japan. Bacterial ooze exuded from lesions, from which a pathogenic bacterium was isolated. Inoculation of blades of perennial ryegrass with the isolates reproduced the same symptoms. Pathogenicity and bacteriological properties of the isolates were almost identical to those of Acidovorax avenae, and the identification was supported by phylogenetic analysis. This is the first report of the brown stripe on perennial ryegrass caused by A. avenae (= A. avenae subsp. avenae) in Japan. [ABSTRACT FROM AUTHOR]

The experiment was to study the allelopathic effect of alfalfa extract on seed germination of perennial ryegrass. The effect of five extracts (0, 2.5, 5.0, 10.0 and 20.0 g/L) from roots, stems and leaves of alfalfa wl-963-HQ on seed germination and seedling growth of perennial ryegrass were determined by Petri dish filter paper method. The results showed that the germination rate, germination potential, germination index and vigor index of the seeds decreased obviously with the increase of the concentration of the extracts from the roots, stems and leaves of alfalfa. The root and leaf extracts of alfalfa had a stronger inhibitory effect on the germination of perennial ryegrass seeds. When the concentration was 20.0 g/L, perennial ryegrass seeds could not germinate normally. Alfalfa extract had no inhibitory effect on root length and seedling height of perennial ryegrass seedlings, but had significant effect on seedling weight. The extracts from the roots, stems and leaves of alfalfa significantly decreased the chlorophyll content of perennial ryegrass seedlings (P<0.05), and the POD activity was significantly increased (P<0.05). Compared with the control group, CAT activity of perennial ryegrass seedlings was significantly increased when the stem extract of alfalfa was 10.0 and 20.0 g/L (P<0.05). The study indicates that alfalfa extract has obvious allelopathy on perennial ryegrass, and reasonable row spacing was needed to reduce allelopathy when the two herbage are mixed. [ABSTRACT FROM AUTHOR]

α-Ketoglutarate (AKG) is a key intermediate metabolite in the tricarboxylic acid cycle of respiration and a precursor for glutamate, playing important roles in regulating plant growth and stress tolerance. The objectives of this study were to examine effects of AKG on heat tolerance characterized by leaf senescence in a cool-season grass species by foliar application and to determine major metabolites and associated metabolic pathways regulated by AKG for its effects on heat tolerance. Perennial ryegrass (Lolium perenne L.) plants were exposed to heat stress (35/30 °C, day/night) or optimal temperature (25/20 °C, day/night, non-stress control) in controlled-environment growth chambers. The solution containing AKG (5 mM) was applied to leaves by spraying 7 d prior to the initiation of heat stress and every 7 d during the heat stress period. Exogenous application of AKG enhanced heat tolerance in perennial ryegrass, as manifested by significant increases in leaf chlorophyll content, photochemical efficiency, and membrane stability, as well as activities of antioxidant enzymes for H 2 O 2 scavenging in AKG-treated plants relative to untreated control plants exposed to heat stress. Metabolic profiling and pathway analysis demonstrated that exogenous AKG application enhanced metabolite accumulation in four major metabolic pathways, including antioxidant metabolism, amino acid metabolism, glycolysis and tricarboxylic acid cycle of respiration, and pyrimidine metabolism, contributing to AKG-improved heat tolerance in perennial ryegrass. • α-Ketoglutarate (AKG) enhanced heat tolerance in perennial ryegrass. • AKG suppressed heat-induced leaf senescence. • AKG regulated the metabolism of antioxidant, amino acids, pyrimidine, glycolysis, and TCA cycle of respiration. [ABSTRACT FROM AUTHOR]

Clubroot, caused by Plasmodiophora brassicae, dramatically reduces yields of brassica crops, and once present in a field, can persist in the soil for many years via long‐lived resting spores. Some nonhost crops can stimulate the germination of resting spores, which reduces clubroot inoculum because the pathogen cannot complete its life cycle in the absence of a living host. The effect of selected grasses and other field crops on the concentrations of spores in soil was assessed in two replicated and repeated short‐duration (8‐week) studies under controlled conditions. The spore concentration declined precipitously in the bare soil control relative to the initial spore concentration over the course of both studies. Cultivars of meadow bromegrass, smooth bromegrass and one cultivar of perennial ryegrass reduced the spore concentration compared to the bare soil control in both repetitions of one study, while two cultivars of perennial ryegrass did not reduce the spore concentration. In a second study, spring wheat, perennial ryegrass, barley and field pea reduced spores compared to the bare soil control, but soybean did not. Our hypothesis that larger root systems would produce larger reductions in spore numbers was not supported; there was no correlation between root weight and reduction in spore concentration. We conclude that perennial grasses, spring cereals and field pea can contribute to the reduction of clubroot spores in soil. The advantage of grass crops over annual crops for clubroot management is that movement of infested soil is minimized over the entire duration of the grass stand. [ABSTRACT FROM AUTHOR]

Context: Insufficient supply of silage has limited the development of animal husbandry in Tibet, where natural pasture may not meet requirements. Although wheat (Triticum aestivum L.) straw could be a supplementary forage, it is difficult to ensile. Mixing perennial ryegrass (Lolium perenne L.) and adding molasses may help to facilitate successful ensilage. Aims: The objectives were to determine the proper mixing ratios of wheat straw and perennial ryegrass for silage, and to evaluate the effects of different levels of molasses on fermentation quality. Methods: In Experiment 1, wheat straw was ensiled without perennial ryegrass or mixed at ratios of 4:1, 3:2 and 2:3 (fresh-weight basis). Fermentation quality was evaluated when the laboratory silos were opened after 7, 14, 30 and 60 days. In Experiment 2, a mixture of wheat straw and perennial ryegrass (2:3) was treated with 0%, 3%, 4% and 5% molasses (fresh-weight basis) and ensiled. Fermentation quality was determined at 7, 14, 30 and 60 days. Key results: In Experiment 1, inclusion of perennial ryegrass significantly (P < 0.05) increased lactic acid and water-soluble carbohydrate contents and the lactic acid:acetic acid ratio, and significantly (P < 0.05) decreased pH and contents of ammonia-nitrogen, acetic acid, butyric acid and total volatile fatty acids. The 2:3 mixture of wheat straw ensiled with perennial ryegrass was judged the best, with the highest lactic acid content and lowest pH and butyric acid content (P < 0.05). In Experiment 2, molasses addition significantly (P < 0.05) increased lactic acid, water-soluble carbohydrate and dry matter contents, and significantly (P < 0.05) decreased pH and ammonia-nitrogen content compared with the control. Trace amounts of propionic and butyric acids were observed in all silages. Fermentation quality was similar among all treatments with added molasses. Conclusions: Considering the costs of additives, 3% molasses was most suitable for practical application when ensiling wheat straw with perennial ryegrass at an optimum ratio of 2:3. Implications: This work may help to inform producers on efficient utilisation of wheat straw for silage making by demonstrating successful ensiling with perennial ryegrass and added molasses. With increasing demand for animal products, natural pasture may not meet the requirements for rapid development of husbandry. We found that ensiling wheat straw with perennial ryegrass favourably affected fermentation quality, with optimum ratio 2:3, and that molasses (3–5%) further improved the fermentation quality of mixed ensilages. The work provides practical guidance for expanding forage sources and improving forage utilisation efficiency. [ABSTRACT FROM AUTHOR]

The productivity of perennial ryegrass (Lolium perenne L.) is constrained by summer water deficit. We hypothesised that selection for desirable water relations traits might partially mitigate this constraint. Genotypes of a 1970s, and two recent ryegrass cultivars were grown in 55 cm tall pots for three months and exposed to moisture deficit for four weeks, then 66 plants were assessed for shoot (SDW) and root (RDW) dry weight, leaf elongation rate (LER), specific water use (SWU), leaf osmotic potential (OP), OP change, leaf relative water content (RWC), and gravimetric soil moisture. Among the 66 genotypes, SWU ranged from 935 ± 19 to 1754 ± 74 g H2O g–1 DM. In principal component (PC) analysis, PC1 indicated greater growth and lower SWU from greater soil water extraction as the common trait association among genotypes tested and ANOVA of PC scores indicated that recent cultivars outperformed the 1970s cultivar. PC2 indicated water saving by decreased LER and SDW, with increased RDW indicative of summer dormancy. PC3 associated more negative OP with improved SWU and RWC. This experiment demonstrates not only genotypic diversity for SWU but also diversity in trait associations determining SWU, which should be considered when investigating SWU, both in ecology and agronomy research. [ABSTRACT FROM AUTHOR]

Salicylic acid (SA) is a plant growth regulator that can enhance the abiotic stress tolerance of plants; however, the physiological mechanisms are not yet fully understood. The objective of this study was to examine whether exogenous SA could enhance the salt tolerance of perennial ryegrass (Loliumperenne L.; PRG) and investigate the physiological underlying mechanisms. SA was applied to the foliage of PRG at five concentrations (0, 0.25, 0.5, and 1 mM). The SA-treated grass was grown under either control (0 mM NaCl) or salt stress (250 mM NaCl) conditions for 24 d. The SA treatments reduced the leaf electrolyte leakage (EL), malonaldehyde (MDA), and hydrogen peroxide (H2O2) content by 36%, 41%, and 40%, respectively, relative to the control under salt stress as measured at 24 d. The SA treatments also alleviated the decline in the leaf photosynthetic rate (Pn), stomatal conductance (gs), nitrate activity (NR), turfgrass quality (TQ) ratings, and chlorophyll (Chl) content under salt stress. In addition, exogenous SA increased the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase (POD) as well as the expression levels of the Cyt Cu/ZnSOD, FeSOD, APX, CAT, and POD genes under salt stress. The results of this study suggested that the foliar application of SA at 0.25 and 0.5 mM may enhance photosynthesis and antioxidant defense systems and thus improve tolerance to salt stress in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Lolium perenne has a global distribution becoming a dominant species in temperate grassland ecosystems and covers a wide range of environmental conditions (length of day, humidity, altitude, soil type and chemistry, etc.). Understanding the patterns and magnitude of the genetic diversity of this allogamous forage species is a first step toward identifying several ecological traits. Intrapopulation genetic diversity can promote the temporal stability of grassland production, and also largescale genetic variation can be closely linked to the regional productivity of perennial ryegrass-dominated grasslands. Although total dry matter production remains a key objective in increasing the productive yield of fodder ryegrass, increased emphasis is placed on seasonal dry matter production, seed quality and density. One of the most important productive traits is leaf length as an important feature of forage grasses, and the development of the molecular marker is an opportunity to identify quantitative trait sites (QTLs) and to begin dissecting the genetic regulation of complex traits. Reproduction for long leaves or for a high rate of leaf elongation should contribute to an improvement in the intercepted radiation accumulated during regrowth and would be a way to improve the spring dry matter yield, but the seed yield has not improved. Selection pressures on seed production criteria applied to the breeding process should improve seed yields without a negative impact on feed performance. The continued success of pasture farming depends on supporting programs to grow fodder species that are able to produce improved varieties that meet market needs by manipulating the recombination of the genome of these fodder plants. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effects of cultivar, nitrogen (N) rate, and biostimulant application on the chemical composition of the aboveground biomass of perennial ryegrass (Lolium perenne L.). A small-area field experiment was established in the Agricultural Experiment Station in Tomaszkowo (53°42′40.8″ N 20°26′04.7″ E, north-eastern Poland). The experiment had a split-plot design with three replications, and the experimental variables were as follows: (i) perennial ryegrass cultivar: Bajka and Baronka, (ii) N fertilizer rate: 0, 120, 240 kg N ha−1, (iii) application of biostimulants: Blatt Boden-Foliar (BB-F) and Blatt Boden-Foliar + Blatt Boden-Multical (BB-F + BB-M). This study demonstrated that the tetraploid cultivar Baronka had a more desirable chemical composition than the diploid cultivar Bajka. The biomass of cv. Baronka had a higher content of CP, CF, and K, and it was characterized by higher leaf greenness (SPAD) values. Nitrogen fertilization considerably increased the content of CP, P, and K, and leaf greenness (SPAD) values in both cultivars, and the noted increase was higher when N was applied at 240 kg ha−1. The N fertilizer rate of 120 kg ha−1 led to a significant decrease in the average Ca content of plants, whereas the N fertilizer rate of 240 kg ha−1 had no significant effect on Ca concentration. The tested biostimulants significantly affected the chemical composition of perennial ryegrass biomass, and their influence was greater when they were applied in combination. The foliar application of Blatt Boden-Foliar and Blatt Boden-Multical increased the content of CP, P, and chlorophyll in perennial ryegrass leaves, whereas it decreased the accumulation of CF, K, and Ca in plants. The analyzed biostimulants had a positive effect on the chemical composition of perennial ryegrass biomass. This is an important practical consideration because high-quality green fodder for livestock can be produced while minimizing the use of mineral fertilizers and adverse environmental impacts. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and arsenic (As) exist simultaneously in soil environment, which poses a serious threat to the safety of agricultural products and forage production. Four Perennial Ryegrass (Lolium perenne L.) cultivars with different accumulation characteristics (ʻNicaraguaʼ, ʻVenusʼ, ʻExcellentʼ and ʻMonroʼ) were selected as the material for pot experiment. The coupled responses of key components and related enzyme activities under combined stresses of Cd and As were investigated. key components contents include Non protein sulfhydryl (NPT), glutathione (GSH) and phytochelatins (PCs). The related enzyme includes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), γ-glutamylcysteine synthetase (γ-ECS), glutathione synthetase (GSS), phytochelatin synthetases (PCSase) and arsenate reductase (AR). The results showed that Cd contents of perennial ryegrass were higher than those of As contents with TFCd/As < 1. Cd and As contents in roots were in the higher proportion than those in shoots. Compared to control, POD activities increased by 2.72 folds under 120 mg kg−1 As treatment. The contents of PCs increased by 5.68 folds under 120 mg kg−1 As treatment. Under combined Cd and As stress, the MDA contents and antioxidant enzyme activities of ʻVenusʼ were higher than those of ʻNicaraguaʼ. ʻNicaraguaʼ, a high accumulation cultivar. Under the combined stresses of Cd and As, the enzyme activities and the key components were significantly correlated (P < 0.05) with the contents of Cd and As. The tolerance to Cd and As was improved with increase in GSH and PCs contents and γ-ECS, GSS, PCSase and AR activities. In conclusion, the antioxidant enzyme system and key resistant substances of perennial ryegrass have important and antagonistic effects on Cd and As stresses. [ABSTRACT FROM AUTHOR]

The wheat sheath miner, Cerodontha australis Malloch (Diptera: Agromyzidae), is a small leaf‐ and stem‐mining fly that is native to New Zealand and eastern Australia where it feeds on grasses and cereals. Although not considered to be a major insect pest of pastures in New Zealand, it can be abundant during spring and summer in Waikato, New Zealand, and infests tillers of the introduced pasture plant, perennial ryegrass, Lolium perenne L. (Poaceae). Cerodontha australis is not deterred from feeding on L. perenne infected with commercially available strains of the fungal endophyte Epichloë festucae var. lolii, which have been shown to provide protection from a range of other insect pests. In this study, three‐pot trials and periodic examination over 18 months of field‐collected L. perenne tillers showed that two Epichloë endophyte strains, AR47 and AR48, reduced the survival and feeding damage by C. australis larvae, but there was no evidence of an effect on adult female feeding or oviposition. Compared to other strains of E. festucae var. lolii endophytes tested, plants infected with AR47 and AR48 had fewer and smaller larvae and less larval mining. The number of tillers with mining was reduced in AR47 relative to endophyte‐free (Nil) by 57.1% (ranging from 25.0 to 92.5% across trials) and in AR48 by 67.1% (26.3–100%). Larvae in AR47 and AR48 were found further from the base of the tiller where they were less likely to damage the meristem and cause tiller death. The number of larvae and pupae in pseudostems was reduced in AR47 and AR48 compared with Nil by 78.4 and 82.0%, respectively, in the field trial. Very few larvae survived to pupation in AR47 and AR48 plants, with a reduction compared to Nil of over 81.5% in AR47 and over 97% in AR48 in each of the four trials presented here. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne) is a widely used cool season turfgrass with outstanding turf quality and grazing tolerance. High temperature is the key factor restricting the distribution of perennial ryegrass in temperate and sub-tropic regions. In this study, we found that one HEAT SHCOK TRANSCRIPTION FACOTR (HSF) class A gene from perennial ryegrass, LpHSFA3 , was highly induced by heat stress. LpHSFA3 is localized in nucleus and functions as a transcription factor. Ectopic overexpression of LpHSFA3 in Arabidopsis improved thermotolerance and rescued heat sensitive deficiency of athsfa3 mutant. Overexpression of LpHSFA3 in perennial ryegrass enhanced heat tolerance and increased survival rate in summer season as evidenced by decreased EL and MDA, increased number of green leaves and total chlorophyll content. LpHSFA3 binds to the HSE region in LpHSFA2a promoter to constitutively activate the expression of LpHSFA2a and downstream heat stress responsive genes. Ectopic overexpression of LpHSFA2a consequently rescued thermal sensitivity of athsfa3 mutant and enhanced thermotolerance of athsfa2 mutant. Perennial ryegrass protoplasts with overexpression of LpHSFA3 and LpHSFA2a exhibited induction of similar subsets of heat responsive genes. These results indicated that transcription factor LpHSFA3 functions as positive regulator of LpHSFA2a to improve thermotolerance of perennial ryegrass, providing further evidence to understand the regulatory networks of plant heat stress response. • LpHSFA3 and LpHSFA2a were significantly induced by heat stresss. • LpHSFA3 improves plant heat tolerance and survival rate in summer season. • LpHSFA3 directly activates the expression of LpHSFA2a. • LpHSFA2a enhances plant heat tolerance. [ABSTRACT FROM AUTHOR]

Grasslands play an important role in contributing to carbon sequestration, soil biogeochemistry and maintaining biodiversity. Genome analysis studies have suggested that species of the subfamily Pooideae have a similar chromosomal structure, being derived from a common ancestor with 7 pairs of chromosomes. Among the species of this family, Lolium perenne stands out due to its high agronomic productivity influenced by climate and soil conditions and hereditary traits such as flowering time. The natural variation at phenotypic and genotypic level is ensured by a reproduction system that requires cross-pollination, producing pronounced genetic variations in the morphological and molecular characteristics of and among its many varieties. Analysis of the frequency and distribution of genetic variation in natural perennial ryegrass populations has supported the view that its center of origin is the Middle East, and its distribution has expanded following a clinical geographic model, most of which is in Europe. At present it is considered that due to its excessive nature and recent domestication the genetic diversity of the varieties is very high. Reproduction programs generate extensive phenotypic data covering the genetic and phenotypic diversity of the germplasm used annually to select the best performing plants or populations. We consider in the light of these scientific results obtained globally that the species Lolium perenne through genetic diversity is a potential resource for the development of reference populations specific to genomic selection. The genetic improvement of perennial ryegrass provides an inexhaustible source of increasingly diverse genetic diversity in the world in terms of the challenges of environmental factors. [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]

Perennial ryegrass (Lolium perenne L.) is a widely sown pasture species in temperate regions. Under heat and moisture-deficit stress, its production is suppressed and tiller mortality increases, particularly when plants are simultaneously exposed to other stresses such as intense defoliation. We investigated the effects of extended grazing exclusion periods in spring and summer on herbage and soils of rotationally grazed, perennial ryegrass-dominant pastures at a summer-wet site and a summer-dry site in sheep and beef hill country in New Zealand. Treatments comprised 'grazed' (conventional rotational grazing), 'early opening' (grazing exclusion from mid-spring to mid-summer to allow perennial ryegrass to flower), and 'deferred grazing' (grazing exclusion from mid-spring to late summer to allow perennial ryegrass to flower and set seed). At both sites, deferred grazing increased perennial ryegrass tiller density and total vegetation cover, and reduced the abundance of broadleaf species and Pseudopithomyces chartarum spores for up to 15 months after exclusion compared with the grazed control. Herbage production was reduced during the deferred period but there was a growth surge thereafter so that herbage production over the study period was similar in the deferred and grazed treatments. Pasture nutritive values were lower in the deferred than the grazed treatment during the exclusion period but were similar in all treatments by the end of the following winter. In the autumn after deferring, seedlings contributed ~50% of the perennial ryegrass tillers present at the summer-dry site but only ~10% at the summer-wet site, where regrowth tillering of existing plants contributed a high proportion of the perennial ryegrass tillers present. Overall, early opening had few effects on the pasture, whereas deferred grazing had numerous positive effects on the pasture but only short-term effects on soil quality. We investigated the impacts of deferred grazing (livestock excluded from mid-spring to late summer to enable perennial ryegrass to flower and set seed), early opening (livestock excluded from mid-spring to early summer to enable perennial ryegrass to flower) and standard rotational grazing on hill country pastures and soils under beef and sheep grazing. Compared with standard rotational grazing, deferred grazing had positive effects on pasture productivity but only short-term effects on soil quality, whereas early opening had few effects on the pastures or soils. [ABSTRACT FROM AUTHOR]

Grazing efficiency has been shown to differ between perennial ryegrass varieties. Such differences affect the utilization of grass within grazing systems, influencing the profitability of grass-based ruminant production systems. The Pasture Profit Index (PPI) is an economic merit grass variety selection tool developed to identify varieties with the greatest economic potential for grass-based dairy production systems. A new grass utilization subindex was developed and incorporated into the PPI to identify varieties with superior grazing efficiency. The subindex rewards varieties with superior grazing efficiency, measured as Residual grazed height, as these varieties allow increased amounts of herbage dry matter to be used by grazing animals. The economic values of all other traits within the PPI were reviewed and updated to ensure that the index was reflective of the current economic scenarios with appropriate assumptions included in the models, thus ensuring that varieties excelling in the agronomic traits with the greatest effect on profitability were recognized. The difference between the highest and lowest performing varieties for the grass utilization trait ranged from €23 to −€24. A range of €211 to €43 was recorded between the highest and lowest ranked varieties within the updated PPI. Spearman's rank correlation between the updated and original PPI lists was 0.96. The introduction of the utilization subindex will allow farmers to make informed variety selection decisions when reseeding pasture, particularly on their grazing platforms and it will allow a demand-based communication process between the farmer and the grass merchant or breeder, ultimately affecting trait selection for future breeding strategies. [ABSTRACT FROM AUTHOR]

Take-all, caused by the fungal pathogen Gaeumannomyces graminis var. tritici (Ggt) is an important root disease of cereals and grasses. An increasing occurrence of very light seeds in some New Zealand perennial ryegrass (Lolium perenne L.) seed crops may have been associated with Ggt, but any Ggt effects on grass seed yield were unknown. A glasshouse experiment, using prairie grass (Bromus wildenowii Kunth) as a model system was used to investigate the effect of Ggt on seed yield in the presence and absence of moisture stress (drought), and to determine whether strains of the fungal symbiont Trichoderma atroviride would allow the plant to better cope with both the biotic and abiotic stresses. Ggt significantly reduced seed yield by reducing the number of seeds per plant, while moisture stress significantly reduced all seed yield components. There was a significant interaction between Ggt and moisture stress because the moisture stress induced seed yield loss was greater in the presence of Ggt than in the absence of Ggt. In the absence of both abiotic and biotic stress, Trichoderma treatment had no effect on seed yield. However, Trichoderma significantly reduced Ggt root infection and this led to an increased seed yield. In the presence of Ggt and moisture stress, Trichoderma further increased seed yield by around double the increase for individual stress. Whether similar responses can be obtained in the field is currently being investigated. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine and compare the sensitivity of new high yield Bulgarian varieties of perennial ryegrass (Lolium perenne L.) - Harmoniya, Tetrany and Tetramis to glyphosate in laboratory conditions. The effect of three doses of glyphosate - 360, 720 and 1440 g a.i./ha applied in the growth stage tillering (BBCH - 22-23) on perennial ryegrass on the dynamics of plant growth and formed fresh biomass in g per plant was studied. Genotypic differences were observed between the studied varieties of perennial ryegrass to glyphosate. With a relatively high sensitivity to glyphosate conditionally can be determined diploid variety Harmoniya in which the depression coefficients (B) on the dynamics of growth and accumulation of fresh biomass are in the range from -5.7 to - 4.7, while for tetraploids Tetrany (B) (average) is in the range of -3.3 to -3.9 and for Tetramis (B) (average) is within limits from -3.2 to -3.9, they have relatively high tolerance to glyphosate and can be used as components in future programs. [ABSTRACT FROM AUTHOR]

Lolium perenne L. (perennial ryegrass) shows variable levels of seed physiological dormancy (PD), which depends on the genotype and environmental condition during seed development. To analyse the effect of field temperature and precipitation during seed filling on the PD, two cultivars were sown on five dates in 2014 and 2015. After harvest, the level of seed PD was 4–28%. High-temperature stress (>29°C) in the field during seed development, measured as heat stress units (HSUs), reduced seed PD (increased germination) at harvest. After 9 months of dry afterripening under laboratory conditions, mean dormant seed values were reduced from 15 ± 8 to 8 ± 7%. An increment in the seed PD level reduced seedling emergence in the field. Seed with 20% PD produced only 50% of field emergence, under optimal environmental conditions. Different vigour tests were conducted and each was compared with field emergence. The speed of germination, through the first count at 5 d of the standard germination test, and the shoot length at 10 d were better associated with the seedling establishment in the field. The HSU could be useful to establish a possible PD range in the seed of perennial ryegrass after the growing season. The development of models considering the HSU and other climatic parameters could motivate future studies. [ABSTRACT FROM AUTHOR]

Background and Aims The persistence of a plant population under a specific local climatic regime requires phenotypic adaptation with underlying particular combinations of alleles at adaptive loci. The level of allele diversity at adaptive loci within a natural plant population conditions its potential to evolve, notably towards adaptation to a change in climate. Investigating the environmental factors that contribute to the maintenance of adaptive diversity in populations is thus worthwhile. Within-population allele diversity at adaptive loci can be partly driven by the mean climate at the population site but also by its temporal variability. Methods The effects of climate temporal mean and variability on within-population allele diversity at putatively adaptive quantitative trait loci (QTLs) were evaluated using 385 natural populations of Lolium perenne (perennial ryegrass) collected right across Europe. For seven adaptive traits related to reproductive phenology and vegetative potential growth seasonality, the average within-population allele diversity at major QTLs (HeA) was computed. Key Results Significant relationships were found between HeA of these traits and the temporal mean and variability of the local climate. These relationships were consistent with functional ecology theory. Conclusions Results indicated that temporal variability of local climate has likely led to fluctuating directional selection, which has contributed to the maintenance of allele diversity at adaptive loci and thus potential for further adaptation. [ABSTRACT FROM AUTHOR]

Despite the progress made in DNA sequencing over the last decade, reconstructing telomere-to-telomere genome assemblies of large and repeat-rich eukaryotic genomes is still difficult. More accurate basecalls or longer reads could address this issue, but no current sequencing platform can provide both simultaneously. Perennial ryegrass (Lolium perenne L.) is an example of an important species for which the lack of a reference genome assembly hindered a swift adoption of genomics-based methods into breeding programs. To fill this gap, we optimized the Oxford Nanopore Technologies' sequencing protocol, obtaining sequencing reads with an N50 of 62 kb—a very high value for a plant sample. The assembly of such reads produced a highly complete (2.3 of 2.7 Gb), correct (QV 45), and contiguous (contig N50 and N90 11.74 and 3.34 Mb, respectively) genome assembly. We show how read length was key in determining the assembly contiguity. Sequence annotation revealed the dominance of transposable elements and repeated sequences (81.6% of the assembly) and identified 38,868 protein coding genes. Almost 90% of the bases could be anchored to seven pseudomolecules, providing the first high-quality haploid reference assembly for perennial ryegrass. This protocol will enable producing longer Oxford Nanopore Technology reads for more plant samples and ushering forage grasses into modern genomics-assisted breeding programs. [ABSTRACT FROM AUTHOR]

To reveal the structural characteristics and physicochemical properties of perennial ryegrass lignin, sequential alkali extractions or double ball-milling and enzymatic hydrolysis on the basis of ultrasonic and hydrothermal pretreatments were proposed in this study. Results revealed that sequential alkali extractions released 89.4% of original lignin from the ryegrass cell walls and 0.75–4.16% of associated carbohydrates as compared to the double ball-milling and enzymatic hydrolysis (96.0% and 18.39%). It was observed that the two types of lignin prepared were SGH-type and had different amounts of p -coumarates and ferulates, and primarily consisted of β-O-4 ′ linkages combined with minor amounts of β-β ′ and β-5 ′ linkages. Besides, alkali-soluble lignins exhibited relatively fewer β-O-4 ′ linkages, higher S/G ratios and H-type units, and abundant phenolic OH groups as compared to the double enzymatic lignin. Overall, the deeper investigation of the lignin structure of ryegrass will provide useful information for the efficient utilization of lignin macromolecules in biorefineries. • Structural characteristic of perennial ryegrass lignin was elucidated in detail. • Two types of lignin prepared by different integrated treatments were SGH-type. • Two types of lignin prepared mainly consisted of β-O-4 ′, β-β ′, and β-5 ′ linkages. • Alkali-soluble lignins had higher purity as compared to double enzymatic lignin. [ABSTRACT FROM AUTHOR]

Pasture management is highly dependent on accurate biomass estimation. Usually, such activity is neglected as current methods are time-consuming and frequently perceived as inaccurate. Conversely, spectral data is a promising technique to automate and improve the accuracy and precision of estimates. Historically, spectral vegetation indices have been widely adopted and large numbers have been proposed. The selection of the optimal index or satisfactory subset of indices to accurately estimate biomass is not trivial and can influence the design of new sensors. This study aimed to compare a canopy-based technique (rising plate meter) with spectral vegetation indices. It examined 97 vegetation indices and 11,026 combinations of normalized ratio indices paired with different regression techniques on 900 pasture biomass data points of perennial ryegrass (Lolium perenne) collected throughout a 1-year period. The analyses demonstrated that the canopy-based technique is superior to the standard normalized difference vegetation index (∆, 115.1 kg DM ha−1 RMSE), equivalent to the best performing normalized ratio index and less accurate than four selected vegetation indices deployed with different regression techniques (maximum ∆, 231.1 kg DM ha−1). When employing the four selected vegetation indices, random forests was the best performing regression technique, followed by support vector machines, multivariate adaptive regression splines and linear regression. Estimate precision was improved through model stacking. In summary, this study demonstrated a series of achievable improvements in both accuracy and precision of pasture biomass estimation, while comparing different numbers of inputs and regression techniques and providing a benchmark against standard techniques of precision agriculture and pasture management. [ABSTRACT FROM AUTHOR]

The type-B response regulator (ARR) family members represent the elements of two-component regulatory systems and play crucial roles in the cytokinin signaling, plant growth, and stress responses. The objective of this study was to characterize type-B ARR genes from perennial ryegrass, and to investigate their roles in regulating to salt tolerance. Twelve type-B ARRs , namely LpARR1 - 12 , were identified in perennial ryegrass. They were clustered into three subgroups and were unevenly distributed on chromosomes. The stress responsive elements (SREs) and hormone responsive elements (HREs) were identified in LpARRs promoters and the transcription of LpARRs genes were responsive to various abiotic stress (heat, salt, and osmotic) and hormonal (cytokinin, ABA, and ethylene) treatments. LpARR10 was strong induced by salt stress, therefore it was selected for function analysis. Overexpressing LpARR10 in Arabidopsis led to a significant improvement in salt tolerance. The LpARR10 -overexpressing (LpARR10 -OE) lines exhibited lower levels of Na+ content compared to WT plants, and the expression levels of SOS1 and SOS3 were significantly higher in the LpARR10 -OE lines. Results of yeast auto-transactivation and plant cell transcriptional activity assays shows LpARR10 is a nucleus localized transcriptional activator and directly bind and transactivated the promoter of SOS1 and SOS3. Together, LpARR10 enhances salt tolerance may via trans-activating SOS1 / SOS3 in Arabidopsis. Knowledge gained in this study will facilitate further functional analysis of LpARRs for molecular breeding of ryegrass and other related grass species. • Overexpressing LpARR10 resulted in a reduction in Na+ content compared to WT plants. • The LpARR10 -OE lines exhibited significantly higher expression levels of SOS1 and SOS3. • LpARR10 acts as a transcriptional activator and positively regulates salt tolerance by up-regulating the expressions of SOS1 and SOS3. [ABSTRACT FROM AUTHOR]

Genotype-by-environment interaction (G×E) is commonly observed in perennial ryegrass species and significantly impacts dry matter yield (DMY) performance across environments. Variation in DMY of perennial ryegrass cultivars and their distinct responses to different environments directly influence the profitability of the Australian dairy industry. In this study, we implemented a separate two-way factor analytic strategy to fit multi-environment-multi-harvest data collected from 18 trials spanning 14 years to account for the G×E effects across complex pasture environments in south-eastern Australia to achieve accurate DMY predictions. Three mega-environments were identified, and the seasonal and environmental DMYs of 126 cultivars or breeding lines (defined by a combination of varieties and endophytes) were predicted. Statistical differences in DMY performance and crossover G×E effects in cultivar rankings were observed among the three mega-environments. Several high-yielding cultivars specific to each mega-environment were also identified. The analysis demonstrated the importance of accounting for G×E effects when predicting the DMY of perennial ryegrass and highlighted the potential for identifying high-yielding cultivars specific to mega-environments. The research rationalizes implementing an appropriate independent pasture trialling system to generate necessary data for the dairy industry and could further facilitate dairy farmers to select suitable cultivars based on their specific environments and perennial ryegrass breeders when accounting for the genetic relationship of cultivars. • G×E impacts perennial ryegrass cultivar rankings and breeding strategies. • Factor analytic model is a robust tool for analysing G×E. • Analysing G×E provides accurate DMY prediction and facilitates identifying high-yielding cultivars. • Identified 3 mega-environments and predicted DMYs for 126 cultivars. • Appling an independent trialling system is necessary to identify environmental-specific cultivars. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne L.) is one of the most important forage grasses, providing high yields with excellent forage quality. The main limiting factor for increasing the cultivation area of perennial ryegrass in the Nordic-Baltic region is insufficient winter hardiness due to unstable climatic conditions as well as insufficient persistence and drought resistance. Currently, the genetic diversity of perennial ryegrass cultivars is relatively limited; therefore, developing new, highly adaptable germplasm is of high importance in the context of changing climatic conditions. In the framework of the Nordic-Baltic Public-Private Partnership (PPP) project in pre-breeding of perennial ryegrass, 250 tetraploid plants (hereinafter genotypes), created by chromosome doubling using colchicine at the Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry, were evaluated in open field conditions at the Research Institute of Agronomy of Latvia University of Life Sciences and Technologies. Detailed phenological scoring of all genotypes was performed over a three-year (2016--2018) period. For data analysis, the plants were grouped according to heading time and growth habit. Significant differences among the groups were found in winterhardiness, regrowth rate, development rate of generative shoots, susceptibility to rust, etc. The seed from plants that survived well and showed some promising properties were harvested in the 2nd ley year -- a total of 199 genotypes or 358 individuals (80% and 48% of all, respectively). Results of genotyping of randomly selected genotypes with the highest and lowest winter hardiness showed that the clones were genetically differentiated from the cultivars developed in Baltic countries -- unique alleles were found in the tetraploid clones that were not present in the analysed cultivars. This suggests that these developed tetraploid clones or genotypes could provide valuable breeding material to improve the suitability of perennial grass cultivars to local environmental conditions in the future. [ABSTRACT FROM AUTHOR]

Ergot, caused by Claviceps purpurea, is a primary disease concern in irrigated cool-season grass seed production systems of Oregon. In order to better understand the genetic diversity, population structure, and the epidemiology of C. purpurea in grasses grown for seed, 226 isolates were obtained using a hierarchical sampling strategy from two fields each of Kentucky bluegrass (n = 102) and perennial ryegrass (n = 124) and characterized using 12 microsatellite markers. A total of 194 unique multilocus genotypes (MLGs) were identified in this study. There were moderate levels of genotypic diversity (H = 3.43 to 4.23) and gene diversity (Hexp = 0.45 to 0.57) within fields. After clone correction, analysis of molecular variance revealed that 66% of the genetic variation occurred between the two C. purpurea isolates collected from the same seed head of individual plants, indicating that many of the seed heads bearing multiple sclerotia were infected by ascospores rather than conidia. However, the majority of the clonal isolates obtained in this study were collected from the same seed head (i.e., the two isolates were identical MLGs), indicating a role of conidia (honeydew) in secondary infections within seed heads. Genetic differentiation was observed between populations from different hosts (22%) but was confounded by geography. The standardized index of association ranged from 0.007 to 0.122 among the four populations, suggesting potential outcrossing and differences in the relative contribution of ascospores and conidia to ergot among the fields. The results from this study provide insights into the epidemiology of ergot in cool-season grass seed crops of Oregon. [ABSTRACT FROM AUTHOR]

• Genome-wide identification and comprehensive analysis of NAC gene family. • LpNAC genes expression analysis under various abiotic stress. • Candidate function gene identification based on phylogenetic analysis. NAC is one of the largest family of plant-specific transcription factors, and it plays important roles in plant development and stress responses. The study identified 72 LpNACs genes from the perennial ryegrass genome database. Gene length, MW and pI of NAC family transcription factors varied, but the gene structure and motifs were relatively conserved in bioinformatics analysis. Phylogenetic analyses of perennial ryegrass, rice and Arabidopsis were performed to study the evolutionary and functional relationships in various species. The expression of LpNAC genes that respond to various abiotic stresses including high salinity, ABA, high temperature, polyethylene glycol (PEG) and heavy metal was comprehensively analyzed. The present study provides a basic understanding of the NAC gene family in perennial ryegrass for further abiotic stress studies and improvements in breeding. [ABSTRACT FROM AUTHOR]

Genomic prediction of nitrogen-use efficiency (NUE) has not previously been studied in perennial grass species exposed to low-N stress. Here, we conducted a genomic prediction of physiological traits and NUE in 184 global accessions of perennial ryegrass (Lolium perenne) in response to a normal (7.5 mM) and low (0.75 mM) supply of N. After 21 d of treatment under greenhouse conditions, significant variations in plant height increment (ΔHT), leaf fresh weight (LFW), leaf dry weight (LDW), chlorophyll index (Chl), chlorophyll fluorescence, leaf N and carbon (C) contents, C/N ratio, and NUE were observed in accessions , but to a greater extent under low-N stress. Six genomic prediction models were applied to the data, namely the Bayesian method Bayes C, Bayesian LASSO, Bayesian Ridge Regression, Ridge Regression-Best Linear Unbiased Prediction, Reproducing Kernel Hilbert Spaces, and randomForest. These models produced similar prediction accuracy of traits within the normal or low-N treatments, but the accuracy differed between the two treatments. ΔHT, LFW, LDW, and C were predicted slightly better under normal N with a mean Pearson r -value of 0.26, compared with r =0.22 under low N, while the prediction accuracies for Chl, N, C/N, and NUE were significantly improved under low-N stress with a mean r =0.45, compared with r =0.26 under normal N. The population panel contained three population structures, which generally had no effect on prediction accuracy. The moderate prediction accuracies obtained for N, C, and NUE under low-N stress are promising, and suggest a feasible means by which germplasm might be initially assessed for further detailed studies in breeding programs. [ABSTRACT FROM AUTHOR]

Genomic selection (GS) is a potential pathway to accelerate genetic gain for perennial ryegrass (Lolium perenne L.). The main objectives of the present study were to investigate the level of genetic gain and accuracy by applying GS in commercial perennial ryegrass breeding programs. Different scenarios were compared to a conventional breeding program. Simulated scenarios differed in the method of selection and structure of the breeding program. Two scenarios (Phen-Y12 and Phen) for phenotypic selection and three scenarios (GS-Y12, GS and GS-SP) were considered for genomic breeding schemes. All breeding schemes were simulated for 25 cycles. The amount of genetic gain achieved was different across scenarios. Compared to phenotypic scenarios, GS scenarios resulted in substantially larger genetic gain for the simulated traits. This was mainly due to more efficient selection of plots and single plants based on genomic estimated breeding values. Also, GS allows for reduction in waiting time for the availability of the superior genetic materials from previous cycles, which led to at least a doubling or a trebling of genetic gain compared to the traditional program. Reduction in additive genetic variance levels were higher with GS scenarios than with phenotypic selection. The results demonstrated that implementation of GS in ryegrass breeding is possible and presents an opportunity to make very significant improvements in genetic gains. [ABSTRACT FROM AUTHOR]

Due to the increasing occurrence of drought events, drought recovery has become equally important as drought resistance for long-term growth and survival of plants. However, information regarding the mechanism that controls growth recovery of herbaceous perennials is not available. In this study, perennial ryegrass (Lolium perenne) was rewatered after eight-day exposure to three drought intensities simulated by polyethylene glycol-6000. The growth, nonstructural carbohydrates (NSC, i.e. sucrose, glucose, fructose and starch), shoot δ 13C, and activities of enzymes for sucrose conversion were monitored for 24 days after rewatering, allowing investigation of the dynamic of NSCs and its relation with growth in the recovery phase. In response to drought, growth and NSC content decreased mainly in shoot rather than root, and the total dry matter was negatively correlated to shoot δ 13C. After rewatering, the growth of drought-treated groups still lagged behind that of control (CK) group for more than 16 days, but it was no longer correlated to shoot δ 13C, suggesting that the limited growth is caused by non-stomatal factors related to photosynthesis. On day 24 after rewatering, the final growth of drought-treated groups caught up or even exceeded that of CK group, and was accompanied by higher dry weight root to shoot ratio (R/S) and root NSC content, which may facilitate water and nutrient acquisition and emergency of new tillers, respectively. During drought and subsequent recovery, the variation of R/S and root NSC content mainly attributed to root acid invertase rather than leaf sucrose phosphate synthase activity. • Legacy effect of drought stress on perennial ryegrass was caused by non-stomatal constraints on photosynthesis. • Recovery of ryegrass from drought stress was associated with increased R/S and elevated carbohydrate content in roots. • Variations in R/S and carbohydrate content in roots of ryegrass during recovery were related to the activity of root InvA. [ABSTRACT FROM AUTHOR]

In New Zealand, a commonly sown pasture combination is perennial ryegrass with white clover. The hydrothermal time model (HTT) was used to quantify germination under different temperature (T) and water potential (WP) conditions for white clover 'Nomad' and perennial ryegrass 'Stellar AR1'. Seeds were germinated in vitro under a range of T × WP combinations, and HTT models were fitted to germination time course data. Rapid germination of white clover under optimum T and WP was reflected by a much lower value for its HTT constant compared with perennial ryegrass (10.8 vs 80.7 MPa °C d). However, the lower base water potential for perennial ryegrass (−1.29 vs −0.495 MPa) and a higher threshold temperature for thermoinhibition (21.8 vs 18.3°C), meant that predicted perennial ryegrass germination was more resilient in warm dry conditions. HTT models can be used to assist decisions about the timing of perennial ryegrass and white clover sowing. [ABSTRACT FROM AUTHOR]

In this paper are shown the results of the production characteristics of the perennial ryegrass (Lolium perenne L.) cv. 'Naki', which grown in rows with different row spacing and seed rate in the agroecological conditions of central Serbia in three successive analysed years. Four levels of two observed factors were used in the experiment: row spacing (12.5; 25; 37.5 and 50 cm) and seed rate (9, 16, 23 and 30 kg ha-1). Due to the analyses, the height of the tiller, the length of the spike and the number of spikelets per spike gave better results by sowing in wider rows (37.5 and 50 cm) using lower seed rate (9 and 16 kg ha-1). Seed yield and harvest index responded favourably to sowing in rows at a wider row spacing (37.5 and 50 cm) in combination with a lower seed rate (9 and 16 kg ha-1), while shoot dry weight gave better results by sowing in narrower rows (12.5 cm) with lower seed rate (9 and 16 kg ha-1). Using the appropriate row spacing in sowing and the optimum of seed rate provides the highest results of the production characteristics of the perennial ryegrass that can be applied to further production. [ABSTRACT FROM AUTHOR]

Perennial ryegrass (Lolium perenne), one of the most widely used forage and cool-season turfgrass worldwide, has a breeding history of more than 100 years. However, the current draft genome annotation and transcriptome characterization are incomplete mainly because of the enormous difficulty in obtaining full-length transcripts. To explore the complete structure of the mRNA and improve the current draft genome, we performed PacBio single-molecule long-read sequencing for full-length transcriptome sequencing in perennial ryegrass. We generated 29,175 high-confidence non-redundant transcripts from 15,893 genetic loci, among which more than 66.88% of transcripts and 24.99% of genetic loci were not previously annotated in the current reference genome. The re-annotated 18,327 transcripts enriched the reference transcriptome. Particularly, 6709 alternative splicing events and 23,789 alternative polyadenylation sites were detected, providing a comprehensive landscape of the post-transcriptional regulation network. Furthermore, we identified 218 long non-coding RNAs and 478 fusion genes. Finally, the transcriptional regulation mechanism of perennial ryegrass in response to drought stress based on the newly updated reference transcriptome sequences was explored, providing new information on the underlying transcriptional regulation network. Taken together, we analyzed the full-length transcriptome of perennial ryegrass by PacBio single-molecule long-read sequencing. These results improve our understanding of the perennial ryegrass transcriptomes and refined the annotation of the reference genome. [ABSTRACT FROM AUTHOR]

During the period 2014-2016 on the experimental field of the Institute of Forage Crops - Pleven a study was conducted with the purpose to determine the selectivity of some herbicides to Bulgarian variety of perennial ryegrass (Lolium perenne L.) IFK Harmoniya during stand establishment and seed production. It was found that herbicides Accurate 60 WG (600 g/kg of metsulfuron-methyl) - 10 g/ha, Ally Max (143 g/kg tribenuron methyl + 143 g/kg metsulfuron methyl) - 35 g/ha and Eagle 75 WG (750 g/kg chlorsulfuron) - 20 g/ha showed high selectivity to perennial ryegrass (Lolium perenne L.) and can be applied at the growth stage BBCH 12-14 on the crop, during establishing year of the stand for control of broadleaf weeds. Accurate 60 WG - 10g/ha and Ally Max - 35 g/ha applied at the growth stage (BBCH 28-30) in the year of seed production had a high selectivity to perennial ryegrass and can be applied for control of broadleaf weeds. Applied low dose of Axial One (45 g/l pinoxadene + 5 g/l florasulam) - 350 ml/ha had hormesis effect to perennial ryegrass and can be used for stimulation the accumulation of fresh and dry biomass during the year of stand establishment and, as well as in the years of seed formation. The herbicide tolerance of perennial ryegrass to key herbicides with complex action (for weed control against annual monocotyledonous and dicotyledonous weeds) has been determined, which could serve as a means of increasing the efficiency of the breeding process. [ABSTRACT FROM AUTHOR]

A mutation causing self‐fertility (SF) in perennial ryegrass was studied at the tetraploid level. The aim of this work was to determine a) whether SF remains functional in a tetraploid population and b) whether the SF mutation expresses dominance in heterozygous pollen grains. A tetraploidized plant carrying SF alleles was self‐pollinated to create a segregating F2 population. In the F2 individuals, pollen compatibility ranged between 38% and 84% showing that SF remained functional. The SF locus genotype was the main determinant of pollen compatibility explaining 78% of the variation. The observed segregation was significantly different from the expected under both SF being dominant or recessive models (P(χ2)≤0.001) and tended to be intermediate between them, indicating partial dominance or additive gene action. The frequency of the different genotypes suggested that pollen grains homozygous for the mutation have a competitive advantage over heterozygous pollen and that pollen compatibility is affected by the interaction with additional loci. The implications of our results for breeding polyploid grasses are discussed. [ABSTRACT FROM AUTHOR]

The study was designed to investigate nitrogen and carbon contents, nitrogen use efficiency, and antioxidants of a tolerant accession PI231578 (TOL) and a susceptible PI306292 (SUS) of perennial ryegrass subjected to 7.5 mM N (control) and 0.75 mM N (low) for 6, 12, and 20 d in a growth chamber. The SUS had decreased plant height, dry matter, shoot carbon content and showed more reductions in leaf chlorophyll and shoot N content at 6, 12 d or 20 d of low N. An increased N use efficiency was greater in the shoots of SUS during the low N treatments and in the roots of TOL at 20 d. Shoot soluble protein content (TSP) was unaffected in TOL but decreased in SUS at 20 d of low N, whereas shoot catalase activity decreased in SUS. Root superoxide dismutase and peroxidase activities increased in TOL at 20 d of low N. [ABSTRACT FROM AUTHOR]

The aim of the study is to determine the variability of morphological characters for the vegetative development of perennial ryegrass collection and to make a selection of genotypes for different directions of use - for fodder and ornamental purposes. During the period 2015-2018 in the Institute of Forage crops - Pleven a collection nursery was studied in fi eld non-irrigated conditions on leached black soil, in block method, in 2 replications of a total of 21 accessions of perennial ryegrass, with 50 individual plants each (15 varieties and 6 ecotypes, 11 tetraploid and 10 diploid, from Bulgaria, Belgium, Romania and China). Mean, minimum, maximum values, standard deviations and variation coefficients for plant height, tuft width at base and top, habitus, number of leaves, leaf length and width, stem thickness, stem number were present. A great genetic diversity was found in the morphological features of the perennial ryegrass collection accessions, both between them and within population. Highest values of variation coefficients (CV) were obtained for plant stems - 43.05%, habitus - 33.85%, leaf length and width - 25.43% and 26.16%, respectively. In the collection the tetraploid varieties have higher plants, longer and broader leaves and more upright habitus, which ensures higher productivity of fodder and for ornamental and amenity purposes are suitable diploid varieties and ecotypes, with lower plants, short and narrow leaves. [ABSTRACT FROM AUTHOR]

Plant growth regulators (PGRs) can mediate plant response to salinity stress. Perennial ryegrass (Lolium perenne) cultivars of BrightStar SLT, Catalina, Inspire, and SR4660ST were exposed to 0, 100, or 200 mM NaCl for 14 d. 6-benzyladenine (6-BA, 10 mM), γ-aminobutyric acid (GABA, 500 mM), nitric oxide (NO, 200 mM), and H2O were applied to the foliage every day for 3 days before stress and then every 2 days during salinity stress. Averaged across the four cultivars, a foliar spray of NO increased leaf fresh weight (FW) and dry weight (DW) at 0 mM NaCl, whereas application of 6-BA increased DW and GABA reduced Na+ concentration at 100 mM NaCl, compared with H2O application. Plants treated with 6-BA, GABA, and NO had less chlorotic and necrotic leaf tissue than plants treated with H2O at 200mM NaCl. Spray of 6-BA and NO increased FW and DW, but application of all three PGRs maintained higher leaf photochemical efficiency and lower leafNa+ concentration compared with H2Otreatment at 200mM NaCl. Across salinity and PGR treatments, 'Catalina' exhibited higher plant height than the 'Inspire' and SR4660ST, and SR4660ST had relatively higher Na+ concentration than 'Catalina' but not 'BrightStar SLT' and 'Inspire'. The results demonstrate that 6-BA, GABA, and NO ameliorated salinity tolerance of perennial ryegrass by improving growth and photochemical efficiency or reducing Na+ accumulation. [ABSTRACT FROM AUTHOR]

Leaf senescence is a prominent symptom of heat injury observed in cool-season plants. The application of melatonin (MT) and inoculation with mycorrhizal fungi can mitigate heat-induced leaf senescence. The current research aims to examine the individual and combined effects of arbuscular mycorrhizal (AM) inoculation and MT application on heat-related leaf senescence in perennial ryegrass (Lolium perenne L.). In addition, whether the effects of these treatments were in any way associated with abscisic acid (ABA), gibberellin (GA), and cytokinin (CTK) for exerting the bioactivity. According to the results, the suppression of heat-mediated leaf senescence using MT treatment and AM inoculation manifested as increased photosynthesis, turf quality (TQ), and plant growth, and reduced membrane lipid peroxidation levels as well as the chlorophyll catabolic genes (CCGs) and senescence-associated genes (LpSAG12.1 and Lph36) transcript levels in the heat-stressed plants. MT application and AM inoculation elevated the internal MT, GA, and CTK levels, while reducing the ABA levels in the heat-stressed plants. In addition, the MT biosynthesis genes (LpTDC1 , LpTDC2 , LpCOMT1 , LpASMT1 , and LpASMT3), the ABA catabolic gene, the GA biosynthesis genes, CTK biosynthesis genes, along with the associated signal transduction response transcription factors (TFs) (type-B ARRs) exhibited increased levels, whereas the expressions of the GA and CTK catabolic genes and the biosynthesis and signal transduction genes related to ABA exhibited decreased levels after MT application and AM inoculation in the heat-stressed plants. Furthermore, the application of exogenous MT notably elevated the AM colonization rate at high temperature (HT) condition. After 28 days of heat stress, compared to the treatment with neither AMF nor MT application, AM combined with MT achieved a synergistic effect, resulting in a 25.32%, 87.21%, 58.69%, 57.17%, and 28.46% increase in TQ, leaf chlorophyll content, net photosynthesis (Pn), leaf photochemical efficiency (Fv/Fm), and relative water content (RWC), respectively, in perennial ryegrass. Additionally, this treatment significantly reduced the electrolyte leakage (EL), hydrogen peroxide (H 2 O 2) and malondialdehyde (MDA) levels by 30.76%, 38.19%, and 31.95%, respectively, and also significantly reduced the transcription levels of CCGs and senescence-associated genes. Consequently, it was inferred that a combination of AM and MT treatments promotes plant growth and development and suppresses heat-induced leaf senescence in plants. • Heat stress induces leaf senescence and inhibits the growth of perennial ryegrass. • AMF and melatonin had synergistic effect on suppressing heat-induced leaf senescence. • AM symbiosis and melatonin down-regulated chlorophyll-degradation genes suppressing senescence. • AM symbiosis and melatonin up-regulated genes for CTK, GA and MT signaling and responses. • AM symbiosis and melatonin down-regulated genes for ABA signaling and responses. [ABSTRACT FROM AUTHOR]

Agricultural systems models are complex and tend to be over-parameterized with respect to observational datasets. Practical identifiability analysis based on local sensitivity analysis has proved effective in investigating identifiable parameter sets in environmental models, but has not been applied to agricultural systems models. Here, we demonstrate that identifiability analysis improves experimental design to ensure independent parameter estimation for yield and quality outputs of a complex grassland model. The Pasture Simulation model (PaSim) was used to demonstrate the effectiveness of practical identifiability analysis in designing experiments and measurement protocols within phenotyping experiments with perennial ryegrass. Virtual experiments were designed combining three factors: frequency of measurements, duration of the experiment. and location of trials. Our results demonstrate that (i) PaSim provides sufficient detail in terms of simulating biomass yield and quality of perennial ryegrass for use in breeding, (ii) typical breeding trials are insufficient to parameterize all influential parameters, (iii) the frequency of measurements is more important than the number of growing seasons to improve the identifiability of PaSim parameters, and (iv) identifiability analysis provides a sound approach for optimizing the design of multi-location trials. Practical identifiability analysis can play an important role in ensuring proper exploitation of phenotypic data and cost-effective multi-location experimental designs. Considering the growing importance of simulation models, this study supports the design of experiments and measurement protocols in the phenotyping networks that have recently been organized. [ABSTRACT FROM AUTHOR]