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Background and Aims In the subfamily Poöideae (Poaceae), certain grass species possess anti-herbivore alkaloids synthesized by fungal endophytes that belong to the genus Epichloë (Clavicipitaceae). The protective role of these symbiotic endophytes can vary, depending on alkaloid concentrations within specific plant–endophyte associations and plant parts. Methods We conducted a literature review to identify articles containing alkaloid concentration data for various plant parts in six important pasture species, Lolium arundinaceum , Lolium perenne , Lolium pratense , Lolium multiflorum | Lolium rigidum and Festuca rubra , associated with their common endophytes. We considered the alkaloids lolines (1-aminopyrrolizidines), peramine (pyrrolopyrazines), ergovaline (ergot alkaloids) and lolitrem B (indole-diterpenes). While all these alkaloids have shown bioactivity against insect herbivores, ergovaline and lolitrem B are harmful for mammals. Key Results Loline alkaloid levels were higher in the perennial grasses L. pratense and L. arundinaceum compared to the annual species L. multiflorum and L. rigidum , and higher in reproductive tissues than in vegetative structures. This is probably due to the greater biomass accumulation in perennial species that can result in higher endophyte mycelial biomass. Peramine concentrations were higher in L. perenne than in L. arundinaceum and not affected by plant part. This can be attributed to the high within-plant mobility of peramine. Ergovaline and lolitrem B, both hydrophobic compounds, were associated with plant parts where fungal mycelium is usually present, and their concentrations were higher in plant reproductive tissues. Only loline alkaloid data were sufficient for below-ground tissue analyses and concentrations were lower than in above-ground parts. Conclusions Our study provides a comprehensive synthesis of fungal alkaloid variation across host grasses and plant parts, essential for understanding the endophyte-conferred defence extent. The patterns can be understood by considering endophyte growth within the plant and alkaloid mobility. Our study identifies research gaps, including the limited documentation of alkaloid presence in roots and the need to investigate the influence of different environmental conditions. [ABSTRACT FROM AUTHOR]

A process of plant recovery after drought cessation is a complex trait which has not been fully recognized. The most important organ associated with this phenomenon in monocots, including forage grasses, is the crown tissue located between shoots and roots. The crown tissue is a meristematic crossroads for metabolites and other compounds between these two plant organs. Here, for the first time, we present a metabolomic and lipidomic study focused on the crown tissue under drought and recovery in forage grasses, important for agriculture in European temperate regions. The plant materials involve high (HDT) and low drought-tolerant (LDT) genotypes of Festuca arundinacea , and Lolium multiflorum/F. arundinacea introgression forms. The obtained results clearly demonstrated that remodeling patterns of the primary metabolome and lipidome in the crown under drought and recovery were different between HDT and LDT plants. Furthermore, HDT plants accumulated higher contents of primary metabolites under drought in the crown tissue, especially carbohydrates which could function as osmoprotectants and storage materials. On the other hand, LDT plants characterized by higher membranes damage under drought, simultaneously accumulated membrane phospholipids in the crown and possessed the capacity to recover their metabolic functions after stress cessation to the levels observed in HDT plants. [ABSTRACT FROM AUTHOR]

Recent plant genomic studies provide fine-grained details on the evolutionary consequences of adaptive introgression during crop domestication. Modern genomic approaches and analytical methods now make it possible to better separate the introgression signal from the demographic signal thus providing a more comprehensive and complex picture of the role of introgression in local adaptation. Adaptive introgression has been fundamental for crop expansion and has involved complex patterns of gene flow. In addition to providing new and more favorable alleles of large effect, introgression during the early stages of domestication also increased allelic diversity at adaptive loci. Previous studies have largely underestimated the effect of such increased diversity following introgression. Recent genomic studies in wheat, potato, maize, grapevine, and ryegrass show that introgression of multiple genes, of as yet unknown effect, increased the effectiveness of purifying selection, and promoted disruptive or fluctuating selection in early cultivars and landraces. Historical selection processes associated with introgression from crop wild relatives provide an instructive analog for adaptation to current climate change and offer new avenues for crop breeding research that are expected to be instrumental for strengthening food security in the coming years. [ABSTRACT FROM AUTHOR]

Loss of chlorophyll and oxidative damage co-occur during heat-induced leaf senescence. This study aimed to determine the functions of a chlorophyll catabolic gene, NON-YELLOW COLOURING 1 (NYC1)-like (NOL), in regulating heat-induced leaf senescence and to characterize antioxidant roles of a chlorophyll derivative, sodium copper chlorophyllin (SCC), in suppressing heat-induced leaf senescence. In two separate experiments, one by comparing NOL RNAi transgenic and wild-type plants, and the other by analysing the effects of SCC treatment, perennial ryegrass (Lolium perenne) was exposed to heat stress (38/35 °C, day/night) or optimal temperature (25/20 °C). Results showed that both knock down of LpNOL and application of SCC suppressed heat-induced leaf senescence, as manifested by increased chlorophyll content, reduced electrolyte leakage, down-regulation of chlorophyll-catabolic genes and senescence-related genes, as well as enhanced antioxidant capacity in the peroxidase pathway for H2O2 scavenging. Ex vivo SCC incubation protected membranes from H2O2 damage in mesophyll protoplasts of perennial ryegrass. The suppression of leaf senescence by knocking down NOL or chlorophyllin application was associated with enhanced chlorophyll accumulation playing antioxidant roles in protecting leaves from heat-induced oxidative damage. [ABSTRACT FROM AUTHOR]

Aim: Potassium (K) is a key determinant for plant development and productivity. However, more than 90% of K in the soil exists in an insoluble form. K‐solubilizing microbes play an important role in the transformation of insoluble K. Thus, the objective of this study was to evaluate K‐dissolving ability of Aspergillus aculeatus (F) and growth‐promoting properties in perennial ryegrass. Methods and Results: Perennial ryegrass inoculated with A. aculeatus exhibited enhanced soluble K accompanied with higher growth rate and turf quality, compared with the noninoculated regimen. In addition, A. aculeatus also played a primary role in increasing chlorophyll content and photosynthetic capacity of the plant exposed to LK+F (K‐feldspar plus A. aculeatus) treatment, compared with the CK (control, no K‐feldspar and A. aculeatus), F (only A. aculeatus) and LK (only K‐feldspar) groups. Furthermore, the antioxidase activities (CAT and POD) were significantly increased while the oxidative damage (EL and MDA) was dramatically decreased in the LK+F group compared to the LK (K‐feldspar) group. Finally, in perennial ryegrass leaves, the genes expression levels of HAK8, HAK12 and HKT18 were obviously elevated in the LK+F group, compared to the CK, F and LK groups. Conclusion: We concluded that A. aculeatus could solubilize K from bound form and be considered as K‐solubilizing biofertilizer through supplementing K in soil. Significance and Impact of the Study: Aspergillusaculeatus has the potential to be used as a biofertilizer in sustainable agriculture. [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]

Background Self-incompatibility (SI) systems prevent self-fertilization in several species of Poaceae, many of which are economically important forage, bioenergy and turf grasses. Self-incompatibility ensures cross-pollination and genetic diversity but restricts the ability to fix useful genetic variation. In most inbred crops it is possible to develop high-performing homozygous parental lines by self-pollination, which then enables the creation of F 1 hybrid varieties with higher performance, a phenomenon known as heterosis. The inability to fully exploit heterosis in outcrossing grasses is partially responsible for lower levels of improvement in breeding programmes compared with inbred crops. However, SI can be overcome in forage grasses to create self-compatible populations. This is generating interest in understanding the genetical basis of self-compatibility (SC), its significance for reproductive strategies and its exploitation for crop improvement, especially in the context of F 1 hybrid breeding. Scope We review the literature on SI and SC in outcrossing grass species. We review the currently available genomic tools and approaches used to discover and characterize novel SC sources. We discuss opportunities barely explored for outcrossing grasses that SC facilitates. Specifically, we discuss strategies for wide SC introgression in the context of the Lolium – Festuca complex and the use of SC to develop immortalized mapping populations for the dissection of a wide range of agronomically important traits. The germplasm available is a valuable practical resource and will aid understanding the basis of inbreeding depression and hybrid vigour in key temperate forage grass species. Conclusions A better understanding of the genetic control of additional SC loci offers new insight into SI systems, their evolutionary origins and their reproductive significance. Heterozygous outcrossing grass species that can be readily selfed facilitate studies of heterosis. Moreover, SC introduction into a range of grass species will enable heterosis to be exploited in innovative ways in genetic improvement programmes. [ABSTRACT FROM AUTHOR]

Background Self-incompatibility (SI) is a physiological mechanism that many flowering plants employ to prevent self-fertilization and maintain heterozygosity. In the grass family this is known to be controlled by a two locus (S - Z) system; however, the SI system is intrinsically leaky. Modifier genes of both the S and Z loci and a further locus, T , are known to override SI leading to self-fertilization and self-seed production. This has implications for the ecological and evolutionary success as well as the commercial breeding of grasses. Here we report a study where the genetic control of self-compatibility (SC) was determined from the results of self-pollinating an F 2 population of perennial ryegrass from two independently derived inbred lines produced by single-seed descent. Methods In vitro self-pollinations of 73 fertile plants were analysed. A genetic association analysis was made with a panel of 1863 single-nucleotide polymorphism (SNP) markers, generated through genotype-by-sequencing methodology. Markers were placed on a recombination map of seven linkage groups (LGs) created using Joinmap v.5. The seed set on self- and open-pollinated inflorescences was determined on 143 plants, including the 73 plants analysed for self-pollination response. Key Results Self-pollinations revealed a bimodal distribution of percentage SC with peaks at 50 and 100 %. A single quantitative trait locus (QTL) was identified with peak association for marker 6S14665z17875_11873 that mapped to LG 6. Peak position was associated with maximum marker segregation distortion. The self-compatible plants were equally fecund after self- and open pollination. Conclusions This is the first report in the Poaceae family of an SC locus located on LG 6. This new SC QTL discovery, as well as indicating the complex nature of the pollen–stigma recognition process and its evolutionary significance, provides an additional source of SC for breeding perennial ryegrass. [ABSTRACT FROM AUTHOR]

Crossing over, in addition to its strictly genetic role, also performs a critical mechanical function, by bonding homologues in meiosis. Hence, it is responsible for an orderly reduction of the chromosome number. As such, it is strictly controlled in frequency and distribution. The well-known crossover control is positive crossover interference which reduces the probability of a crossover in the vicinity of an already formed crossover. A poorly studied aspect of the control is chromatid interference. Such analyses are possible in very few organisms as they require observation of all four products of a single meiosis. Here, we provide direct evidence of chromatid interference. Using in situ probing in two interspecific plant hybrids (Lolium multiflorum×Festuca pratensis and Allium cepa×A. roylei) during anaphase I, we demonstrate that the involvement of four chromatids in double crossovers is significantly more frequent than expected (64% versus 25%). We also provide a physical measure of the crossover interference distance, covering ~30–40% of the relative chromosome arm length, and show that the centromere acts as a barrier for crossover interference. The two arms of a chromosome appear to act as independent units in the process of crossing over. Chromatid interference has to be seriously addressed in genetic mapping approaches and further studies. [ABSTRACT FROM AUTHOR]

Age at puberty in bovine heifers is controlled largely by genetic and environmental factors, among which nutrition has a major influence. This study evaluated the utility of cool-season forages for heifer development in a limited-resource beef cow-calf system. Beef heifer development was evaluated at 4 time periods: Period 1 (Birth-Weaning) heifers sucked dams until weaning, Period 2 (Weaning-Puberty) heifers grazed natural pastures and supplements in Fall and Winter, Period 3 (Puberty-Breeding) heifers grazed cool-season forages, Period 4 (Breeding-Pregnancy) heifers were maintained on Spring and Summer forages. The supplements were fed at a rate of 0.45 kg/68.2 kg. calf BW and consisted of a 1:1 ratio of cracked corn and commercial grower pellets. Cool-season pasture consisted mainly of Rye grass and clovers. Hay, water, and minerals were provided free choice. Heifer body weights were obtained at quarterly intervals. They were synchronized with two doses of prostaglandin F (PGF) 2a, 14 days apart before bull introduction on June 1st. Pregnancy was confirmed by ultrasonography at the end of breeding in August. The growth trajectory was evaluated by mixed procedures of SAS. A stair-step pattern of body weight gain was observed from birth to pregnancy. There was rapid growth pre-weaning, average daily gain (ADG) = 0.95 ± 0.0.17kg ·heifer-1·day-1. Limited growth during the juvenile period (ADG = 0.24 ± 0.17kg·heifer-1·day-1) and compensatory growth during the pre-pubertal period (ADG = 1.32 ± 0.17kg·heifer-1·day-1). These preliminary results indicate that limited-resource beef cow-calf producers should utilize winter forages to leverage compensatory growth in their heifer development programs. Funded by FAMU World Class Scholars Program and NIFA CBG # 2021-38821-34599. [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]

The natural genetic diversity of agricultural species is an essential genetic resource for breeding programs aiming to improve their ecosystem and production services. A large natural ecotype diversity is usually available for most grassland species. This could be used to recombine natural climatic adaptations and agronomic value to create improved populations of grassland species adapted to future regional climates. However describing natural genetic resources can be long and costly. Molecular markers may provide useful information to help this task. This opportunity was investigated for Lolium perenne L., using a set of 385 accessions from the natural diversity of this species collected right across Europe and provided by genebanks of several countries. For each of these populations, genotyping provided the allele frequencies of 189,781 SNP markers. GWAS were implemented for over 30 agronomic and/or putatively adaptive traits recorded in three climatically contrasted locations (France, Belgium, Germany). Significant associations were detected for hundreds of markers despite a strong confounding effect of the genetic background; most of them pertained to phenology traits. It is likely that genetic variability in these traits has had an important contribution to environmental adaptation and ecotype differentiation. Genomic prediction models calibrated using natural diversity were found to be highly effective to describe natural populations for almost all traits as well as commercial synthetic populations for some important traits such as disease resistance, spring growth or phenological traits. These results will certainly be valuable information to help the use of natural genetic resources of other species. [ABSTRACT FROM AUTHOR]

By modifying two genes involved in lipid biosynthesis and storage [cysteine oleosin (cys-OLE)/diacylglycerol O -acyltransferase (DGAT)], the accumulation of stable lipid droplets in perennial ryegrass (Lolium perenne) leaves was achieved. Growth, biomass allocation, leaf structure, gas exchange parameters, fatty acids, and water-soluble carbohydrates were quantified for a high-expressing cys-OLE/DGAT ryegrass transformant (HL) and a wild-type (WT) control grown under controlled conditions with 1–10 mM nitrogen (N) supply at ambient and elevated atmospheric CO2. A dramatic shift in leaf carbon (C) storage occurred in HL leaves, away from readily mobilizable carbohydrates and towards stable lipid droplets. HL exhibited an increased growth rate, mainly in non-photosynthetic organs, leading to a decreased leaf mass fraction. HL leaves, however, displayed an increased specific leaf area and photosynthetic rate per unit leaf area, delivering greater overall C capture and leaf growth at high N supply. HL also exhibited a greater photosynthesis response to elevated atmospheric CO2. We speculate that by behaving as uniquely stable microsinks for C, cys-OLE-encapsulated lipid droplets can reduce feedback inhibition of photosynthesis and drive greater C capture. Manipulation of many genes and gene combinations has been used to increase non-seed lipid content. However, the cys-OLE/DGAT technology remains the only reported case that increases plant biomass. We contrast cys-OLE/DGAT with other lipid accumulation strategies and discuss the implications of introducing lipid sinks into non-seed organs for plant energy homeostasis and growth. [ABSTRACT FROM AUTHOR]

Forage nutritive value impacts animal nutrition, which underpins livestock productivity, reproduction and health. Genetic improvement for nutritive traits in perennial ryegrass has been limited, as they are typically expensive and time-consuming to measure through conventional methods. Genomic selection is appropriate for such complex and expensive traits, enabling cost-effective prediction of breeding values using genome-wide markers. The aims of the present study were to assess the potential of genomic selection for a range of nutritive traits in a multi-population training set, and to quantify contributions of family, location and family-by-location variance components to trait variation and heritability for nutritive traits. The training set consisted of a total of 517 half-sibling (half-sib) families, from five advanced breeding populations, evaluated in two distinct New Zealand grazing environments. Autumn-harvested samples were analyzed for 18 nutritive traits and maternal parents of the half-sib families were genotyped using genotyping-by-sequencing. Significant (P, 0.05) family variance was detected for all nutritive traits and genomic heritability (h2 g) was moderate to high (0.20 to 0.74). Family-by-location interactions were significant and particularly large for water soluble carbohydrate (WSC), crude fat, phosphorus (P) and crude protein. GBLUP, KGD-GBLUP and BayesCp genomic prediction models displayed similar predictive ability, estimated by 10-fold cross validation, for all nutritive traits with values ranging from r = 0.16 to 0.45 using phenotypes from across two locations. High predictive ability was observed for the mineral traits sulfur (0.44), sodium (0.45) and magnesium (0.45) and the lowest values were observed for P (0.16), digestibility (0.22) and high molecular weight WSC (0.23). Predictive ability estimates for most nutritive traits were retained when marker number was reduced from one million to as few as 50,000. The moderate to high predictive abilities observed suggests implementation of genomic selection is feasible for most of the nutritive traits examined. [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]

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]

Chl breakdown is a hallmark of leaf senescence. Protein degradation is tightly associated with accelerated Chl catabolism during leaf senescence. Therefore, blocking or reducing Chl breakdown and thereby improving Chl and leaf protein contents is desirable for agronomic improvement in perennial forage grasses. Perennial ryegrass (Lolium perenne L.) is one principle cool-season forage grass in temperate areas throughout the world. In this study, the perennial ryegrass STAY-GREEN gene (LpSGR) was cloned and characterized. LpSGR was highly expressed in developmentally or dark-induced senescent leaves. LpSGR was subcellularly localized in chloroplast and interacted with the other Chl catabolic enzymes. RNA interference (RNAi) of LpSGR in perennial ryegrass blocked the degradation of Chl, resulting in increased Chl content and photochemical efficiency in senescent leaves. The RNAi transgenic plants had significantly improved forage quality, with up to 46.1% increased protein content in the harvested biomass. Transcriptome comparison revealed that suppression of LpSGR led to multiple alterations in metabolic pathways in locations inside the chloroplast. Most transcription factors of senescence-associated hormonal signaling pathways (e.g. ABA, ethylene and jasmonic acid) had decreased expression levels in the RNAi plants. These results provided a foundation for the further study on the regulatory mechanism of LpSGR in perennial ryegrass for the purpose of forage improvement with delayed leaf senescence and higher forage quality. [ABSTRACT FROM AUTHOR]

Tall fescue (Schedonorus arundinaceus) is the predominant cool-season perennial forage in the Eastern U.S. However, a symbiotic endophyte reduces performance of animals grazing tall fescue. This results in losses of around $2 billion annually. Due to the vasoconstriction caused by the endophyte, a decrease in conception rates among cows and heifers consuming tall fescue has been observed. With rising input costs, it is necessary to explore alternative mitigation strategies these production losses. The objective of this study was to mitigate the toxic effects of 'KY 31' tall fescue by limit-grazing cool-season annuals as an alternative to feed supplementation. In January 2022, 48 heifers [14 months of age; 365.9 ± 11.89 kg body weight (BW)] were randomly assigned to tall fescue only, tall fescue with supplemental feed at 1% of BW, tall fescue with limit grazing of cool-season annuals for 24 h per week, and cool-season annuals only. Four animals grazed in each of three replicated paddocks per treatment. Cool-season annual pasture was a mixture of crimson clover (Trifolium incarnatum), annual ryegrass (Lolium multiflorum), and oat (Avena sativa). Body condition scores (BCS), hair coat scores (HCS), and BW were recorded every 30 d. Forage samples were taken for biomass, nutritive value, and ergovaline concentration every 30 d. On April 1, 2022, heifers were artificially inseminated (AI), and conception rates were determined 45 d after AI. Data were analyzed using the Glimmix procedure of SAS 9.4 (SAS Inst, Cary, NC) with a = 0.05. There were no differences among treatments in HCS at any weigh date (P > 0.05). The BCS for all treatments was less in February than January or March (5.6, 6.1, 6.1, respectively; P < 0.0001), but there were no differences among treatments at any sampling date (P > 0.05). Conception rates were not different among treatments (P > 0.10) but averaged 75, 67, 42, and 50% for the continuous-cool season, limit graze, supplemental feed, and tall fescue treatments, respectively. Crude protein (CP) concentrations for the control and limit grazing fescue treatments were greater than the limit grazing cool-season annual treatment, continuous grazing cool-season annual treatment, and the supplemental feed treatment (13.5, 10.7, 10.4, and 8.9%, respectively, (P < 0.012). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were different among the supplemental treatment when compared with the limit grazing fescue, limit grazing cool-season annual, control, and continuous cool-season annual (48.2 vs 64.7% NDF and 25.8 vs. 37.0% ADF; P < 0.0361). At this time, the results indicate that limit grazing coolseason annual forages may be an advantageous option to mitigate fescue toxicosis in replacement heifers grazing tall fescue pastures in the spring. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effects of concentrate supplementation levels on performance and DM intake of early-weaned beef calves consuming annual ryegrass (Lolium multiflorium). The experiments were conducted at the UF/IFAS Range Cattle Research and Education Center, Ona, FL from January to May 2022. In experiment 1, treatments were two levels of concentrate supplementation (0.75% or 1.0% of BW) distributed in a randomized complete block design with four replicates. Concentrate was fed daily and had 18% CP and 78% TDN. Thirty-two Angus crossbred calves were weaned with 90 ± 14 kg BW at 76 ± 10 d of age and allocated to 1 of 8 annual ryegrass pastures (experimental units; 0.3 ha/pasture; 4 calves/pasture) with a continuous and fixed stocking rate. Herbage mass and nutritive value were estimated every 14 d and calves were weighed every 28 d. There was no difference in herbage mass (mean = 1.300 kg DM/ha; P = 0.44; SE = 0.46), herbage allowance (mean = 0.86 kg DM/kg LW; P = 0.66; SE = 0.03), CP (mean = 24.4%; P = 0.46; SE = 0.78), and in vitro digestible organic matter (mean = 77%; P = 0.49; SE = 1) concentration between treatments. There was a treatment × month interaction on ADG and the interaction occurred because calves receiving 1% BW had greater ADG than 0.75% BW in April (1.0 vs. 0.8 kg/d; P = 0.04; 0.03) but there were no differences between treatments in February, March, and May. In experiment 2, treatments were supplementation with 0.75% or 1.0% BW concentrate distributed in a complete randomized design with seven replicates. Fourteen steers calves (166 ± 17 kg BW) from experiment 1 were maintained in the same treatment, transferred to a drylot (1 steer/pen), and evaluated for forage and total DM intake, and in vivo DM digestibility. Ground annual ryegrass hay (11% CP, 58% IVDOM) was offered and adjusted to allow 10% refusals. There was no difference in forage DM intake (mean = 1.8 kg DM/d; P = 0.3; SE = 0.06) between treatments but calves receiving 1.0% BW had greater total DM intake (2.7 vs. 2.5 kg DM/d; P = 0.05; SE = 0.06) and in vivo DM digestibility (77 vs. 75%; P < 0.01; SE = 0.53) than 0.75% BW. Decreasing concentrate supplementation level from 1.0 to 0.75% BW may be a viable management practice to reduce cost of developing early weaned beef calves grazing annual ryegrass. [ABSTRACT FROM AUTHOR]

In grassland plant communities, the ability of individual plants to regrow after defoliation is of crucial importance since it allows the restoration of active photosynthesis and plant growth. The aim of this study was to evaluate the effects of increasing defoliation intensity (0, 25, 65, 84, and 100% of removed leaf area) on sugar remobilization and N uptake, remobilization, and allocation in roots, adult leaves, and growing leaves of ryegrass over 2 days, using a 15N tracer technique. Increasing defoliation intensity decreased plant N uptake in a correlative way and increased plant N remobilization, but independently. The relative contribution of N stored before defoliation to leaf growth increased when defoliation intensity was severe. In most conditions, root N reserves also contributed to leaf regrowth, but much less than adult leaves and irrespective of defoliation intensity. A threshold of defoliation intensity (65% leaf area removal) was identified below which C (glucose, fructose, sucrose, fructans), and N (amino acids, soluble proteins) storage compounds were not recruited for regrowth. By contrast, nitrate content increased in elongating leaf bases above this threshold. Wounding associated with defoliation is thus not the predominant signal that triggers storage remobilization and controls the priority of resource allocation to leaf meristems. A framework integrating the sequential events leading to the refoliation of grasses is proposed on the basis of current knowledge and on the findings of the present work. [ABSTRACT FROM AUTHOR]

Immature pollen can be induced to switch developmental pathways from gametogenesis to embryogenesis and subsequently regenerate into homozygous, diploid plants. Such androgenic production of doubled haploids is particularly useful for species where inbreeding is hampered by effective selfincompatibility systems. Therefore, increasing the generally low androgenic capacity of perennial ryegrass (Lolium perenne L.) germplasm would enable the efficient production of homozygous plant material, so that a more effective exploitation of heterosis through hybrid breeding schemes can be realized. Here, we present the results of a genome-wide association study in a heterozygous, multiparental population of perennial ryegrass (n = 391) segregating for androgenic capacity. Genotyping-by-sequencing was used to interrogate gene-dense genomic regions and revealed over 1,100 polymorphic sites. Between one and 10 quantitative trait loci (QTL) were identified for anther response, embryo and total plant production, green and albino plant production and regeneration. Most traits were under polygenic control, although a major QTL on linkage group 5 was associated with green plant regeneration. Distinct genetic factors seem to affect green and albino plant recovery. Two intriguing candidate genes, encoding chromatin binding domains of the developmental phase transition regulator, Polycomb Repressive Complex 2, were identified. Our results shed the first light on the molecular mechanisms behind perennial ryegrass microspore embryogenesis and enable marker-assisted introgression of androgenic capacity into recalcitrant germplasm of this forage crop of global significance. [ABSTRACT FROM AUTHOR]

Bovine respiratory disease (BRD) is the leading cause of morbidity and mortality in beef cattle. Common management practices in addition to BRD have been shown previously to cause inflammation. The objectives of this study were: (1) characterize the inflammatory profiles as indicated by haptoglobin concentrations, over a receiving period in high-risk cattle; (2) evaluate the impact of on-arrival metaphylactic antimicrobial therapy on inflammatory profiles in high risk cattle; and (3) examine the relationship between inflammatory profile and BRD morbidity and mortality in high risk cattle. This 70 d trial was repeated over two years. A total of 160 black/black white face crossbred heifers were acquired from local auction markets and randomly assigned at arrival to treatment groups. Heifers were purchased by an order buyer from auction barns. At arrival, heifers were randomly assigned to either receive tulathromycin (Draxxin, META, n = 40) or not (NO META, n = 40) upon arrival. Each group was housed on a 10-acre pasture planted in annual ryegrass where they were offered complete commercial supplemental feed (14% CP) and free choice (both Purina Animal Nutrition, Nashville, TN) mineral and were observed daily for clinical signs of BRD. Cattle were weighed and blood was collected every seven days from d0 to d20, and again on d70. Haptoglobin concentrations were determined using ELISA. Effects of treatment and morbidity on haptoglobin concentration were tested using the MIXED procedure of SAS. Overall morbidity was 28.5%. Initial body weight (227 kg META, 229 kg NO META, P > 0.10) did not differ between the two treatment groups. However, final body weight differed between treatment groups (294 kg META, 289kg NO META). Haptoglobin concentrations remained elevated over time for all groups (P = 0.03). Metaphylaxis did not affect haptoglobin concentration (P > 0.10). There was a significant increase in BRD cases from day 0 to 20 (P = 0.00). Morbidity (BRD vs no BRD) did not impact haptoglobin concentrations. Overall, metaphylaxis did not affect haptoglobin levels or BRD incidence. [ABSTRACT FROM AUTHOR]

Nitrogen excretion from sheep production systems is an important source of nitrate, ammonia, and nitrous oxide responsible for groundwater pollution and global warming. The present study aimed to identify key parameters influencing N utilization efficiency and develop prediction equations for manure N, feces N, and urine N outputs in sheep. Data used were collected from 82 sheep offered fresh perennial ryegrass (Lolium perenne) as the sole diet in 6 metabolism experiments (data from non-grassonly diets were not used). Sheep were from breeds of Highlander, Texel, Scottish Blackface, and Swaledale at the age of 5 to 18 mo and weighing from 24.5 to 62.7 kg. Herbage was harvested daily from 6 swards of contrasting harvest dates (May to December), offering wide variation in feed value to cover the range that would be offered in most practical farm situations. Before the commencement of each study, the experimental sward was harvested at a residual height of 4 cm and allowed to grow for 2 to 4 wk to target an average pregrazing sward height in a range of 8 to 15 cm depending on the time of year. Sheep were housed in individual pens for 14 d and then transferred to individual metabolism crates for 4 d with feed intake and feces and urine outputs measured. Data were analyzed using the linear mixed model procedure to develop prediction equations for feces N, urine N, and manure N outputs using N intake, herbage chemical composition, and digestibility with effects of sex, breed, and experimental periods removed. Nitrogen intake was the best single predictor for N output in feces, urine, and manure, and the r² value for prediction of manure N output was greater than those for feces N and urine N (0.86 vs. 0.70 and 0.77, respectively; P < 0.001). Animal BW and herbage DM, ether extract, NDF, ADF, water soluble carbohydrate, and DE concentrations and N digestibility were also used to predict N outputs because N intake may not be available in commercial practice. The prediction equations for N utilization efficiency indicated that increasing feeding level and ME concentration and reducing N concentration could improve N utilization efficiency and shift N excretion into feces rather than urine (P < 0.001). The equations developed in the current study provide an approach for sheep producers to quantify N excretion against production and, consequently, to develop their own mitigation strategies to reduce the environmental impact of sheep production systems. [ABSTRACT FROM AUTHOR]

Secreted proteins, those involved in cell wall biogenesis, are likely to play a role in communication in the symbiotic interaction between the fungal endophyte Epichlo¨e festucae with perennial ryegrass (Lolium perenne), particularly given the close association between fungal hyphae and the plant cell wall. Our hypothesis was that secreted proteins are likely to be responsible for establishing and maintaining a normal symbiotic relationship. We analyzed an endophyte EST database for genes with predicted signal peptide sequences. Here, we report the identification and characterization of rhgA; a gene involved in the regulation of hyphal growth in planta. In planta analysis of ΔrhgA mutants showed that disruption of rhgA resulted in extensive unregulated hyphal growth. This phenotype was fully complemented by insertion of the rhgA gene and suggests that rhgA is important for maintaining normal hyphal growth during symbiosis. [ABSTRACT FROM AUTHOR]

Aims Effects of culture conditions on productivity, germinability and bioactivity of Trichoderma atroviride LU132 conidia were assessed to identify the factors affecting conidium 'fitness' (quantity and quality) and to withstand variable environmental conditions, increase conidial productivity, and perform optimum bioactivity. Methods and Results The interaction effects of temperatures (20 or 30°C) vs hydrocarbon types (dextrose or sucrose in constant C : N 5 : 1) were assessed for bioactivity and colonization potential in pot experiments with ryegrass in the presence of pathogen, Rhizoctonia solani. Trichoderma atroviride produced in different culture conditions increased some growth parameters of ryegrass plant and also reduced the pathogenicity effects of R. solani. For example, Trichoderma colony produced at 20°C with sucrose increased all plant growth parameters and conidia produced at 20°C with dextrose gave the greatest bioactivity. Conclusion The bimodal population cycle in T. atroviride recurred in pot experiments in a manner similar to that previously observed in agar plates but indicating that simulated natural conditions shortened the Trichoderma life cycle. Trichoderma colonized ryegrass root system and symbiotically interacted with ryegrass and greater ryegrass colonization resulted from medium production treatment with dextrose rather than sucrose. Significance and Impact of the Study This study is the first report on the effects of inoculum production conditions on conidium quality of Trichoderma to colonize and to maintain populations in host rhizospheres, and also the ability to promote plant growth and suppress a soil-borne disease. The results of these experiments provide new knowledge on how manipulation of culture conditions of T. atroviride LU132 can influence conidium fitness, as a basis for optimizing commercial production of the fungus as a biological control agent. [ABSTRACT FROM AUTHOR]

Remote sensing has opened doors for grazing management by allowing producers to monitor forage in a more efficient way. The objective of this study was to observe the relationship between the normalized vegetation index (NDVI) from images taken by an unmanned aerial vehicle (UAV) to nutritive value parameters. This project took place at the H. H. Leveck Animal Research Center located in Starkville, MS where 9, 2-hectare pastures planted in Marshall annual ryegrass (Lolium multiflorum) were utilized. Each 2-hectare pasture was subdivided into 0.20-hectare sections where forage samples were collected from 3, 1/4 of a meter quadrat every 14-days. Images were taken with UAV over a 76-day grazing period every 14-days. Images from the UAV were captured at 121.9 m above ground level using a DJI inspire 2 rotor wing fitted with a MicaSense RedEdge camera (MicaSense; Seattle, WA). Images were processed using Pix4D (Pix4D SA; Prilly, Switzerland) and analyzed in QGIS (QGIS; OSGeo; Finland). Raster calculator in QGIS was utilized to calculate NDVI values. Forage samples were analyzed using NIR for crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), relative forage quality (RFQ), and invitro dry matter digestibility (IVDMD) and correlated to NDVI values. Regression analysis was conducted in R (RStudio, PBC) using the package easynls (easynls-package) procedure within package ggplot2 (ggplot2-package). Regression models were obtained through a backward-elimination technique. Neutral detergent fiber (r² = 0.27) had the best correlated relationship to NDVI compared with CP (r² = 0.21), ADF (r² = 0.25), RFQ (r² = 0.18), and IVDMD (r² = 0.22). As NDVI values increased, CP, RFQ, and IVDMD increased while ADF and NDF decreased. There was a weak correlation between all nutritive value parameters and NDVI values. In conclusion, weak relationships indicate that NDVI values may not be the best predictor of nutritive value. [ABSTRACT FROM AUTHOR]

• Background and Aims High density genetic linkage maps that are extensively anchored to assembled genome sequences of the organism in question are extremely useful in gene discovery. To facilitate this process in perennial ryegrass (Lolium perenne L.), a high density single nucleotide polymorphism (SNP)- and presence/absence variant (PAV)-based genetic linkage map has been developed in an F2 mapping population that has been used as a reference population in numerous studies. To provide a reference sequence to which to align genotyping by sequencing (GBS) reads, a shotgun assembly of one of the grandparents of the population, a tenth-generation inbred line, was created using Illumina-based sequencing. • Methods The assembly was based on paired-end Illumina reads, scaffolded by mate pair and long jumping distance reads in the range of 3-40 kb, with >200-fold initial genome coverage. A total of 169 individuals from an F2 mapping population were used to construct PstI-based GBS libraries tagged with unique 4-9 nucleotide barcodes, resulting in 284 million reads, with approx. 1.6 million reads per individual. A bioinformatics pipeline was employed to identify both SNPs and PAVs. A core genetic map was generated using high confidence SNPs, to which lower confidence SNPs and PAVs were subsequently fitted in a straightforward binning approach. • Key Results The assembly comprises 424 750 scaffolds, covering 1.11 Gbp of the 2.5 Gbp perennial ryegrass genome, with a scaffold N50 of 25 212 bp and a contig N50 of 3790 bp. It is available for download, and access to a genome browser has been provided. Comparison of the assembly with available transcript and gene model data sets for perennial ryegrass indicates that approx. 570 Mbp of the gene-rich portion of the genome has been captured. An ultra-high density genetic linkage map with 3092 SNPs and 7260 PAVs was developed, anchoring just over 200Mb of the reference assembly. • Conclusions The combined genetic map and assembly, combined with another recently released genome assembly, represent a significant resource for the perennial ryegrass genetics community. [ABSTRACT FROM AUTHOR]

Development of effective methane (CH4) mitigation strategies for grazing sheep requires accurate prediction tools. The present study aimed to identify key parameters influencing enteric CH4 emissions and develop prediction equations for enteric CH4 emissions from sheep offered fresh grass. The data used were collected from 82 sheep offered fresh perennial ryegrass (Lolium perenne) as sole diets in 6 metabolism experiments (data from non-grass-only diets were not used). Sheep were from breeds of Highlander, Texel, Scottish Blackface, and Swaledale at the age of 5 to 18 mo and weighing from 24.5 to 62.7 kg. Grass was harvested daily from 6 swards on contrasting harvest dates (May to December). Before the commencement of each study, the experimental sward was harvested at a residual height of 4 cm and allowed to grow for 2 to 4 wk. The feeding trials commenced when the grass sward was suitable to zero grazing (average grass height = 15 cm), thus offering grass of a quality similar to what grazing animals would receive under routine grazing management. Sheep were housed in individual pens for 14 d and then moved to individual calorimeter chambers for 4 d. Feed intake, fecal and urine outputs, and CH4 emissions were measured during the final 4 d. Data were analyzed using the REML procedure to develop prediction equations for CH4 emissions. Linear and multiple prediction equations were developed using BW, DMI, GE intake (GEI), and grass chemical concentrations (DM, OM, water-soluble carbohydrates [WSC], NDF, ADF, nitrogen [N], GE, DE, and ME) as explanatory variables. The mean CH4 production was 21.1 g/kg DMI or 0.062 MJ/MJ GEI. Dry matter intake and GEI were much more accurate predictors for CH4 emissions than BW (P < 0.001, r2 = 0.86 and r2 = 0.87 vs. r2 = 0.09, respectively). Adding grass DE and ME concentrations and grass nutrient concentrations (e.g., OM, N, GE, NDF, and WSC) to the relationships between DMI or GEI and CH4 emissions improved prediction accuracy with R2 values increased to 0.93. Models based on farm-level data, for example, BW and grass nutrient (i.e., DM, GE, OM, and N) concentrations, were also developed and performed satisfactorily (P < 0.001, R2 = 0.63). These models can contribute to improve prediction accuracy for enteric CH4 emissions from sheep grazing on ryegrass pasture. [ABSTRACT FROM AUTHOR]

Aims The purpose of this study was to investigate the effects of compaction and air infiltration on the bacterial community structure during the fermentation process and the aerobic exposure phase of grass silage. Methods and Results Perennial ryegrass was ensiled at laboratory scale in a high-density ( HD) and low-density ( LD) compaction variant. Silages were exposed to air, and degradation was monitored by analysing temperature changes within the silage. Fermentation dynamics were examined using chemical analysis and terminal restriction fragment length polymorphism ( TRFLP) analysis of the 16S rRNA gene supported by cloning and sequencing of representative samples. Dominant Lactobacillus species in HD silages remained largely unchanged during aerobic exposure. LD silages revealed fundamental changes in the bacterial community structure when exposed to air. After 4 days aerobic storage, only 23% of the primary silage community remained and mainly opportunistic Bacillus species proliferated. Conclusion The ensiling of ryegrass is a very dynamic microbial process. Aerobic spoilage was limited to the LD silages, marked by a complete change towards a Bacillus-dominated community. Significance and Impact of the Study The TRFLP analysis supported by the identification of terminal restriction fragments, revealed novel insights into the dynamics of the bacterial community during ensiling, and at aerobic spoilage conditions. [ABSTRACT FROM AUTHOR]

Aims To search for culturable Burkholderia species associated with annual ryegrass in soils from natural pastures in Portugal, with plant growth-promoting effects. Methods and Results Annual ryegrass seedlings were used to trap Burkholderia from two different soils in laboratory conditions. A combined approach using genomic fingerprinting and sequencing of 16S rRNA and recA genes resulted in the identification of Burkholderia strains belonging to the species Burkholderia graminis, Burkholderia fungorum and the Burkholderia cepacia complex. Most strains were able to solubilize mineral phosphate and to synthesize indole acetic acid; some of them could produce siderophores and antagonize the phytopathogenic oomycete, Phytophthora cinnamomi. A strain (G2Bd5) of B. graminis was selected for gnotobiotic plant inoculation experiments. The main effects were the stimulation of root growth and enhancement of leaf lipid synthesis and turnover. Fluorescence in situ hybridization and confocal laser microscopy evidenced that strain G2Bd5 is a rhizospheric and endophytic colonizer of annual ryegrass. Conclusions This work revealed that annual ryegrass can naturally associate with members of the genus Burkholderia. A novel plant growth promoting strain of B. graminis was obtained. Significance and Impact of the Study The novel strain belongs to the plant-associated Burkholderia cluster and is a promising candidate for exploitation as plant inoculant in field conditions. [ABSTRACT FROM AUTHOR]

Chlorophyll (Chl) degradation occurs naturally during leaf maturation and senescence, and can be induced by stresses, both processes involving the regulation of plant hormones. The objective of this study was to determine the functional roles and hormonal regulation of a gene encoding pheophytin pheophorbide hydrolyase (PPH) that catabolizes Chl degradation during leaf senescence in perennial grass species. A PPH gene, LpPPH, was cloned from perennial ryegrass (Lolium perenne L.). LpPPH was localized in the chloroplast. Overexpressing LpPPH accelerated Chl degradation in wild tobacco, and rescued the stay-green phenotype of the Arabidopsis pph null mutant. The expression level of LpPPH was positively related to the extent of leaf senescence. Exogenous application of abscisic acid (ABA) and ethephon (an ethylene-releasing agent) accelerated the decline in Chl content in leaves of perennial ryegrass, whereas cytokinin (CK) and aminoethoxyvinylglycine (AVG; an ethylene biosynthesis inhibitor) treatments suppressed leaf senescence, corresponding to the up- or down-regulation of LpPPH expression. The promoters of five orthologous PPH genes were predicted to share conserved cis-elements potentially recognized by transcription factors in the ABA and CK pathways. Taken together, the results suggested that LpPPH-mediated Chl breakdown could be regulated positively by ABA and ethylene, and negatively by CK, and LpPPH could be a direct downstream target gene of transcription factors in the ABA and CK signaling pathways. [ABSTRACT FROM AUTHOR]

This study investigated successional colonization of fresh perennial ryegrass (PRG) by the rumen microbiota over time. Fresh PRG was incubated in sacco in the rumens of three Holstein × Friesian cows over a period of 8 h, with samples recovered at various times. The diversity of attached bacteria was assessed using 454 pyrosequencing of 16S rRNA (cDNA). Results showed that plant epiphytic communities either decreased to low relative abundances or disappeared following rumen incubation, and that temporal colonization of the PRG by the rumen bacteria was biphasic with primary (1 and 2 h) and secondary (4-8 h) events evident with the transition period being with 2-4 h. A decrease in sequence reads pertaining to Succinivibrio spp. and increases in Pseudobutyrivibrio, Roseburia and Ruminococcus spp. (the latter all order Clostridiales) were evident during secondary colonization. Irrespective of temporal changes, the continually high abundances of Butyrivibrio, Fibrobacter, Olsenella and Prevotella suggest that they play a major role in the degradation of the plant. It is clear that a temporal understanding of the functional roles of these microbiota within the rumen is now required to unravel the role of these bacteria in the ruminal degradation of fresh PRG. [ABSTRACT FROM AUTHOR]

We have developed a new methodology to assess individual perennial ryegrass plant performance under moisture stress and identified QTLs associated with improved performance during drought in this important forage species.Periodic drought events present a significant and, with climate change, increasing constraint on temperate forage plants’ production. Consequently, improving plants’ adaptive response to abiotic stress is a key goal to ensure agricultural productivity in these regions. In this study we developed a new methodology, using both area-based comparison and soil water content measurements of individual non-irrigated and irrigated clones, to assess performance of perennial ryegrass (Lolium perenne L.) genotypes subjected to moisture stress in a simulated competitive environment. We applied this method to the evaluation of a full-sibling population from a pair cross between genotypes from a New Zealand cultivar and a Moroccan ecotype. Our hypothesis was that: (i) both leaf lamina regrowth after defoliation (LR) and plant vigour affect plant performance during drought and rehydration; and (ii) quantitative trait loci (QTLs) associated with plant performance under moisture stress could be identified. Differences amongst genotypes in dry matter (DM) production, early vigour at establishment, leaf elongation rate and LR were measured. LR explained most of the variation in DM production during exposure to moisture deficit and rehydration followed by plant vigour, indicated by initial DM production in both treatments and subsequent measures of DM production of irrigated clones. We identified two main QTL regions associated with DM production and LR, both during drought exposure and rehydration. Further research focused on these regions should improve our understanding of the genetic control of drought response in this forage crop and potentially other grass species with significant synteny, and support improvement in performance through molecular breeding approaches. [ABSTRACT FROM AUTHOR]

Grazing management is heading towards a more digitized world where producers can use technology such as satellite imagery, drone imagery and global positioning system (GPS) data sets for matching real-time forage availability to livestock nutritional needs. The objective of this study was to compare vegetative indices between unmanned aerial vehicles (UAV) and satellite imagery to observe changes in forage mass in relation to environment and grazing pressure. This project took place at the H. H. Leveck Animal Research Center located in Starkville, MS where nine, two-hectare pastures planted in Marshall annual ryegrass (Lolium multiflorum) were utilized. Each pasture was monitored with a satellite and UAV over a 76-day grazing period with images taken every 14-days. Images from the UAV were captured at 121.9 m above ground level using a DJI inspire 2 rotor wing fitted with a MicaSense RedEdge camera (MicaSense®; Seattle,WA). Satellite images were captured using a constellation of satellites from Planet (Plant Labs Inc.; San Francisco, CA). Images were processed using Pix4D (Pix4D SA; Prilly, Switzerland) and analyzed in ArcGIS (ArcGIS; Esri; Redlands, CA). Normalized vegetation index (NDVI) was calculated for both imagery platforms. In addition, forage samples were collected for future analysis every 14-days to calculate biomass and observe forage nutritive value. Each UAV image was resampled using cubic convolution to match spatial resolution of the satellite image. Raster calculator in ArcGIS was utilized to calculate NDVI values between images. Reported NDVI value data were analyzed in the NPAR1WAY procedure of SAS® software, Version 9.4 (SAS Institute, Cary, NC, 2013). using a significance level of α = 0.05. Greenness of vegetation was significantly greater (P< 0.0001) for the UAV compared to the satellite imagery with NDVI being 0.80 compared to 0.78 respectively. In conclusion, vegetation observed by UAV imagery reports greater density of green vegetation. [ABSTRACT FROM AUTHOR]

Aims A fungal endophyte, Neotyphodium uncinatum, accumulates N-formylloline, which is toxic to Hemipteran insects, in Italian ryegrass. This study aimed to clarify the dynamics of N. uncinatum and N-formylloline in Italian ryegrass, and their relationship to insect resistance. Methods and Results Changes in the density and localization of N. uncinatum and N-formylloline in N. uncinatum-infected Italian ryegrass were examined by real-time PCR and gas chromatography, respectively. Neotyphodium uncinatum multiplied on pseudostems at the flowering stage, and then increased on inflorescences at the ripening stage. On the other hand, N-formylloline accumulated heavily in inflorescences and leaf blades, but lightly in pseudostems at the ripening stage. In field experiments, N. uncinatum-infected Italian ryegrass suppressed the occurrence of Stenotus rubrovittatus, which fed on the inflorescences, but was not effective to Laodelphax striatellus, which do not necessarily prefer a particular plant tissue. Conclusion Localization of N. uncinatum and N-formylloline were discordant in Italian ryegrass. The N. uncinatum-infected Italian ryegrass was effective to only insects that prefer to feed on particular plant tissues containing N-formylloline. Significance and Impact of Study Our data implies that the relationship between insect habits and the dynamics of alkaloids in plants is important for the effective use of endophyte-infected crops. [ABSTRACT FROM AUTHOR]

The analysis of large genomes is hampered by a high proportion of repetitive DNA, which makes the assembly of short sequence reads difficult. This is also the case in meadow fescue (Festuca pratensis), which is known for good abiotic stress resistance and has been used in intergeneric hybridization with ryegrasses (Lolium spp.) to produce Festulolium cultivars. In this work, we describe a new approach to analyze the large genome of meadow fescue, which involves the reduction of sample complexity without compromising information content. This is achieved by dissecting the genome to smaller parts: individual chromosomes and groups of chromosomes. As the first step, we flow sorted chromosome 4F and sequenced it by Illumina with approximately 50 × coverage. This provided, to our knowledge, the first insight into the composition of the fescue genome, enabled the construction of the virtual gene order of the chromosome, and facilitated detailed comparative analysis with the sequenced genomes of rice (Oryza sativa), Brachypodium distachyon, sorghum (Sorghum bicolor), and barley (Hordeum vulgare). Using GenomeZipper, we were able to confirm the collinearity of chromosome 4F with barley chromosome 4H and the long arm of chromosome 5H. Several new tandem repeats were identified and physically mapped using fluorescence in situ hybridization. They were found as robust cytogenetic markers for karyotyping of meadow fescue and ryegrass species and their hybrids. The ability to purify chromosome 4F opens the way for more efficient analysis of genomic loci on this chromosome underlying important traits, including freezing tolerance. Our results confirm that next-generation sequencing of flow-sorted chromosomes enables an overview of chromosome structure and evolution at a resolution never achieved before. [ABSTRACT FROM AUTHOR]

Bermudagrass is often over-seeded with a cool-season annual grass for grazing purposes. In the Gulf Coast region, summer perennials will not become dormant until there are low soil and ambient temperatures. Nitrogen fertilizer is an expensive input and its split application for winter pastures is recommended. The objective of this experiment was to evaluate the time of application of N fertilizer or its substitution with red clover as a source of N. Three treatments were evaluated in 3 consecutive years (2 replicates per year) on annual ryegrass (cv. Marshall) no-tilled planted (45 kg/ha) on Tifton-85 bermudagrass: 1) Urea in late November and mid-late January; 2) Red clover planted with annual ryegrass; 3) Urea in January only. Thirty crossbred steers (203±24 kg) were blocked by BW and randomly assigned to 1 of 6 groups. Each group were continuously stocked on 1.34 ha pastures for 90 d. Forage mass, botanical composition, and nutritive value of the pastures were determined from the time of the first N application and every 15 d thereafter. There was treatment x year interaction (P = 0.03) in botanical composition. Greater proportions (P = 0.03) of bermudagrass were present on the 2-application treatment on every sampling date until d 15 of the grazing period in Year 1 and 3. This was a result of N absorbed by bermudagrass which impacted its nutritive value (P = 0.01) although not forage production (P = 0.07). In Year 2, annual ryegrass dominated the swards due to a cold artic front in early November. Steers grazing fertilized treatments had greater gains (P = 0.04), while production per ha was greater (P = 0.03) when N was applied in January than when no N was applied. Hay production (kg DM/ha) was similar (P = 0.06) among treatments. Opportunities for improved economics of production and enhanced sustainability appear to be realistic objectives with changes in fertilization strategy. [ABSTRACT FROM AUTHOR]

Grazing sward structure can influence animal performance in forage-only and forage plus concentrate-based production systems. The objective was to determine the effects of pre-grazing herbage mass (PGHM), postgrazing sward height (PGSH) and indoor finishing diet on performance of weaned, spring-born beef steers. Steers (n = 96, ca. 12 months of age, 396 ± 20.1 kg) previously fed grass silage only over the first winter, were assigned to one of twelve grazing groups, balanced for live weight. Grazing groups were randomly assigned to a two PGHM (1500 or 2500 kg DM/ha) × two PGSH (4 or 6 cm) factorial arrangement of treatments (n = 3 groups/treatment). Steers rotationally grazed Lolium perenne-dominant swards (not mechanically topped) for 222 days. Steers were then accommodated indoors and offered grass silage only (SO) or grass silage + 3.8 kg concentrate DM/head daily (SC) for a 146 day finishing period. Data were analysed using the mixed procedure of SAS with terms for PGHM, PGSH, finishing diet and their interactions in the model. Grazed herbage intake was unaffected by PGHM but was greater for PGSH-6 than PGSH-4 (6.94 vs. 6.18 kg DM/day; P < 0.001). Steer average daily gain at pasture was greater for PGHM-1500 than PGHM-2500 (0.65 vs. 0.60 kg; P < 0.05) and for PGSH-6 than PGSH-4 (0.70 vs. 0.55 kg; P < 0.001). After indoor finishing, carcass weight was unaffected by PGHM, but was heavier for PGSH-6 than PGSH-4 (386 vs. 367 kg; P < 0.01); carcass traits were unaffected by PGHM or PGSH. Carcasses were heavier (+43 kg), fatter (P < 0.001) and more conformed (P < 0.01) for SC than SO. In conclusion, both PGHM-2500 and PGSH-4 restricted animal growth at pasture; however, following an indoor finishing period, carcass weight did not differ between PGHM, but was heavier for PGSH-6 than PGSH-4. [ABSTRACT FROM AUTHOR]

A farmlet study was established to evaluate the effect of four sward types on the performance of heifers and lambs co-grazing: a perennial ryegrass only sward (PRG) receiving 170 kg N/ha each year; a permanent pasture (PP) receiving 135 kg N/ha each year; a six species mix (2 grasses, 2 legumes, 2 herbs) at 70 kg N/ha each year (6SP); and a 12 species mix (3 grasses, 4 legumes and 5 herbs) at 70 kg N/ha each year (12SP). Each farmlet (9 ha) was rotationally grazed with 20 dairy cross heifers (13 months old) and 22 ewes plus lambs from April to November 2020. Heifers and lambs were finished for slaughter from herbage only diets. Heifers were weighed monthly and drafted for slaughter on three occasions when their estimated fat class on the EUROP grid scale reached 3-. Lambs were weighed fortnightly and drafted for slaughter at 42 kg [lambing to weaning (July 7th)], 44 kg (weaning to September) and 46 kg (after September 1st) to obtain a target carcass weight of 21 kg. Average daily gain (ADG) was higher for heifers grazing the 6SP sward (1.13 kg/day) than the PRG (0.99 kg/day) or PP swards (1.03 kg/day; P < 0.05). Kill out percentage (KO%) was higher for heifers grazing the 12SP sward (48.9%) compared to the PP sward (47.2%; P < 0.01). Lamb ADG was higher for lambs grazing the 6SP sward (0.38kg/day) compared to lambs grazing either the PP (0.32kg/day) or the PRG sward (0.29kg/day) (P < 0.01). Lamb KO% was higher for lambs grazing the 12SP sward (49.4%) compared to those grazing the PRG (45.7%) and the PP swards (44.5%; P < 0.01). Lambs grazing the 6SP sward had reduced days to slaughter (109) compared to lambs grazing the PP (137) and PRG (149) swards (P < 0.01). In conclusion, co-grazing multispecies swards improved overall heifer and lamb performance. [ABSTRACT FROM AUTHOR]

Drought is a major environmental stress limiting growth of perennial grasses in temperate regions. Plant drought tolerance is a complex trait that is controlled by multiple genes. Candidate gene association mapping provides a powerful tool for dissection of complex traits. Candidate gene association mapping of drought tolerance traits was conducted in 192 diverse perennial ryegrass (Lolium perenne L.) accessions from 43 countries. The panel showed significant variations in leaf wilting, leaf water content, canopy and air temperature difference, and chlorophyll fluorescence under well-watered and drought conditions across six environments. Analysis of 109 simple sequence repeat markers revealed five population structures in the mapping panel. A total of 2520 expression-based sequence readings were obtained for a set of candidate genes involved in antioxidant metabolism, dehydration, water movement across membranes, and signal transduction, from which 346 single nucleotide polymorphisms were identified. Significant associations were identified between a putative LpLEA3 encoding late embryogenesis abundant group 3 protein and a putative LpFeSOD encoding iron superoxide dismutase and leaf water content, as well as between a putative LpCyf Cu-ZnSOD encoding cytosolic copper-zinc superoxide dismutase and chlorophyll fluorescence under drought conditions. Four of these identified significantly associated single nucleotide polymorphisms from these three genes were also translated to amino acid substitutions in different genotypes. These results indicate that allelic variation in these genes may affect whole-plant response to drought stress in perennial ryegrass. [ABSTRACT FROM AUTHOR]

Background and Aims There are many unresolved issues concerning the biochemistry of fructan biosynthesis. The aim of this paper is to address some of these by means of modelling mathematically the biochemical processes. Methods A model has been constructed for the step-by-step synthesis of fructan polymers. This is run until a steady state is achieved for which a polymer distribution is predicted. It is shown how qualitatively different distributions can be obtained. Key Results It is demonstrated how a set of experimental results on polymer distribution can by simulated by a simple parameter adjustments. Conclusions Mathematical modelling of fructan biosynthesis can provide a useful tool for helping elucidate the details of the biosynthetic processes. [ABSTRACT FROM PUBLISHER]

Tall fescue [Lolium arundinaceum (Schreb.) Darbysh. syn. Festuca arundinacea Schreb.] and perennial ryegrass (Lolium perenne L.) are impor-tant perennial forage grasses utilized throughout the moderate- to high-rainfall temperate zones of the world. These grasses have coevolved with symbiotic fungal endophytes (Epichloe/Neotyphodium spp.) that can impart bioactive properties and environmental stress tolerance to the grass compared with endophyte-free individuals. These endophytes have proven to be very important in pastoral agriculture in the United States, New Zealand, and Australia, where forage grasses are the principal feed for grazing ruminants. In this review, we describe the biology of these grass-endophyte associations and implications for the livestock indus-tries that are dependent on these forages. Endophyte alkaloid production is put in context with endophyte diversity, and we illustrate how this has facilitated uti-lization of grasses infected with different endophyte strains that reduce livestock toxicity issues. Utilization of tall fescue and use of perennial ryegrass in the United States, New Zealand, and Australia are compared, and management strategies focused predominantly on the success of endophyte-infected perennial ryegrass in New Zealand and Australia are discussed. In addition, we consider the impact of grass-endophyte associations on the sustainability of pasture ecosystems and their likely response to future changes in climate. [ABSTRACT FROM AUTHOR]

This study tested the hypotheses that: (i) genetic variation in Rubisco turnover may exist in perennial ryegrass (Lolium perenne L.); (ii) such variation might affect nitrogen use efficiency and plant yield; and (iii) genetic control of Rubisco turnover might be amenable to identification by quantitative trait loci (QTL) mapping. A set of 135 full-sib F1 perennial ryegrass plants derived from a pair cross between genotypes from the cultivars ‘Grasslands Impact’ and ‘Grasslands Samson’ was studied to test these hypotheses. Leaf Rubisco concentration at different leaf ages was measured and modelled as a log-normal curve described by three mathematical parameters: D (peak Rubisco concentration), G (time of D), and F (curve standard deviation). Herbage dry matter (DM) yield and morphological traits (tiller weight (TW), tiller number (TN), leaf lamina length (LL), and an index of competitive ability (PI)) were also measured. The progeny exhibited continuous variation for all traits. Simple correlation and principal component analyses indicated that plant productivity was associated with peak Rubisco concentration and not Rubisco turnover. Lower DM was associated with higher leaf Rubisco concentration indicating that Rubisco turnover effects on plant productivity may relate to energy cost of Rubisco synthesis rather than photosynthetic capacity. QTL detection by a multiple QTL model identified seven significant QTL for Rubisco turnover and nine QTL for DM and morphological traits. An indication of the genetic interdependence of DM and the measures of Rubisco turnover was the support interval overlap involving QTL for D and QTL for TN on linkage group 5 in a cluster involving QTL for DM and PI. In this region, alleles associated with increased TN, DM, and PI were associated with decreased D, indicating that this region may regulate Rubisco concentration and plant productivity via increased tillering. A second cluster involving QTL for LL, TN, PI and DM was found on linkage group 2. The two clusters represent marker-trait associations that might be useful for marker-assisted plant breeding applications. In silico comparative analysis indicated conservation of the genetic loci controlling Rubisco concentration in perennial ryegrass and rice. [ABSTRACT FROM AUTHOR]

This study investigated successional colonization of perennial ryegrass ( PRG) by the rumen microbiota. PRG grown for 6 weeks in a greenhouse was incubated in sacco in the rumens of three Holstein × Freisian cows over a period of 24 h. PRG incubated within the rumen was subsequently harvested at various time intervals postincubation to assess colonization over time. DGGE-based dendograms revealed the presence of distinct primary (0-2 h) and secondary (4 h onwards) attached bacterial communities. Moving window analysis, band number and Shannon- Wiener diversity indices suggest that after 2 h a proportion of primary colonizing bacteria detach, to be replaced with a population of secondary colonizing bacteria between 2 and 4 h after entry of PRG into the rumen. Sequencing and classification of bands lost and gained between 2 and 4 h showed that the genus Prevotella spp. was potentially more prevalent following 4 h of incubation, and Prevotella spp. 16 S r DNA-based QPCR supported this finding somewhat, as 2- to 4-h Prevotella QPCR data were greater but not significantly so. Low-temperature scanning electron microscopy showed that attached bacteria were predominantly enveloped in extracellular polymeric substances. In conclusion, colonization of fresh PRG is biphasic with primary colonization completed within 2 h and secondary colonization commencing after 4 h of attachment in this study. [ABSTRACT FROM AUTHOR]

Whole-genome sequences established for model and major crop species constitute a key resource for advanced genomic research. For outbreeding forage and turf grass species like ryegrasses (Lolium spp.), such resources have yet to be developed. Here, we present a model of the perennial ryegrass (Lolium perenne) genome on the basis of conserved synteny to barley (Hordeum vulgare) and the model grass genome Brachypodium (Brachypodium distachyon) as well as rice (Oryza sativa) and sorghum (Sorghum bicolor). A transcriptome-based genetic linkage map of perennial ryegrass served as a scaffold to establish the chromosomal arrangement of syntenic genes from model grass species. This scaffold revealed a high degree of synteny and macrocollinearity and was then utilized to anchor a collection of perennial ryegrass genes in silico to their predicted genome positions. This resulted in the unambiguous assignment of 3,315 out of 8,876 previously unmapped genes to the respective chromosomes. In total, the GenomeZipper incorporates 4,035 conserved grass gene loci, which were used for the first genome-wide sequence divergence analysis between perennial ryegrass, barley, Brachypodium, rice, and sorghum. The perennial ryegrass GenomeZipper is an ordered, information-rich genome scaffold, facilitating map-based cloning and genome assembly in perennial ryegrass and closely related Poaceae species. It also represents a milestone in describing synteny between perennial ryegrass and fully sequenced model grass genomes, thereby increasing our understanding of genome organization and evolution in the most important temperate forage and turf grass species. [ABSTRACT FROM AUTHOR]

The daily BW gain of stocker steers grazing tall fescue [Lolium arundiriaceum (Schreb.) S.J. Darbysh. = Schedonorus arundinaceus (Schreb.) Dumort.]-based pastures typically declines during summer. To avoid these declines, in part to mitigate the effects of tall fescue toxicosis, it is commonly advised to move cattle to warm-season forage during this period. A 3-yr (2006, 2007, and 2008) grazing study was conducted to evaluate the effect of replacing 25% of the area of a tall fescue/clover (81% endophyte-infected) pasture system with "Ozark" bermudagrass [Cynodon dactylon (L.) Pers.] overseeded with clover (Trifolium spp.) to provide summer grazing for stocker steers (TF+BERM). The TF+BERM treatment was compared with a grazing system in which tall fescue/clover (TF) pastures were the only type of forage available for grazing. Our objective was to determine if replacement of 25% of the land area in a fescue system with bermudagrass would increase annual beef production compared with a system based solely on tall fescue. The study was conducted at the Southwest Research and Education Center of the University of Missouri near Mt. Vernon. Each treatment was rotationally stocked with 5 steers (248 ± 19.3 kg) on 1.7 ha. Fertilizer applications were applied at rates recommended for each respective forage species. Total forage production, BW gain per hectare, and season-long ADG of steers was greater (P < 0.06) for TF+BERM than for TF in 2006, but none of these measures differed (P > 0.19) in 2007 or 2008. In vitro true digestibility of pastures was greater (P = 0.01) for TF (84.4%, SEM = 0.64%) compared with TF+BERM (80.6%, SEM = 0.79%), even in summer. The decreased in vitro true digestibility of the bermudagrass pastures likely negated any benefit that animals in TF+BERM had in avoiding the ergot-like alkaloids associated with endophyte-infected tall fescue. Renovating 25% of the pasture system to bermudagrass provided some benefit to the system in years when summertime precipitation was limited (2006) but provided no value in wetter years (2007 and 2008). Although renovating endophyte-infected tall fescue pastures to a warm-season forage is a widely used practice to mitigate tall fescue toxicosis, the benefits of this practice are limited if forage quality of the warm season component is poor. [ABSTRACT FROM AUTHOR]