Genotypes Of Lolium Perenne Research Articles

Seasonal Differences in Structural and Genetic Control of Digestibility in Perennial Ryegrass.

Perennial ryegrass is an important forage crop in dairy farming, either for grazing or haying purposes. To further optimise the forage use, this study focused on understanding forage digestibility in the two most important cuts of perennial ryegrass, the spring cut at heading and the autumn cut. In a highly diverse collection of 592 Lolium perenne genotypes, the organic matter digestibility (OMD) and underlying traits such as cell wall digestibility (NDFD) and cell wall components (cellulose, hemicellulose, and lignin) were investigated for 2 years. A high genotype × season interaction was found for OMD and NDFD, indicating differences in genetic control of these forage quality traits in spring versus autumn. OMD could be explained by both the quantity of cell wall content (NDF) and the quality of the cell wall content (NDFD). The variability in NDFD in spring was mainly explained by differences in hemicellulose. A 1% increase of the hemicellulose content in the cell wall (HC.NDF) resulted in an increase of 0.81% of NDFD. In autumn, it was mainly explained by the lignin content in the cell wall (ADL.NDF). A 0.1% decrease of ADL.NDF resulted in an increase of 0.41% of NDFD. The seasonal traits were highly heritable and showed a higher variation in autumn versus spring, indicating the potential to select for forage quality in the autumn cut. In a candidate gene association mapping approach, in which 503 genes involved in cell wall biogenesis, plant architecture, and phytohormone biosynthesis and signalling, identified significant quantitative trait loci (QTLs) which could explain from 29 to 52% of the phenotypic variance in the forage quality traits OMD and NDFD, with small effects of each marker taken individually (ranging from 1 to 7%). No identical QTLs were identified between seasons, but within a season, some QTLs were in common between digestibility traits and cell wall composition traits confirming the importance of hemicellulose concentration for spring digestibility and lignin concentration in NDF for autumn digestibility.

Applying RGB- and Thermal-Based Vegetation Indices from UAVs for High-Throughput Field Phenotyping of Drought Tolerance in Forage Grasses

The persistence and productivity of forage grasses, important sources for feed production, are threatened by climate change-induced drought. Breeding programs are in search of new drought tolerant forage grass varieties, but those programs still rely on time-consuming and less consistent visual scoring by breeders. In this study, we evaluate whether Unmanned Aerial Vehicle (UAV) based remote sensing can complement or replace this visual breeder score. A field experiment was set up to test the drought tolerance of genotypes from three common forage types of two different species: Festuca arundinacea, diploid Lolium perenne and tetraploid Lolium perenne. Drought stress was imposed by using mobile rainout shelters. UAV flights with RGB and thermal sensors were conducted at five time points during the experiment. Visual-based indices from different colour spaces were selected that were closely correlated to the breeder score. Furthermore, several indices, in particular H and NDLab, from the HSV (Hue Saturation Value) and CIELab (Commission Internationale de l’éclairage) colour space, respectively, displayed a broad-sense heritability that was as high or higher than the visual breeder score, making these indices highly suited for high-throughput field phenotyping applications that can complement or even replace the breeder score. The thermal-based Crop Water Stress Index CWSI provided complementary information to visual-based indices, enabling the analysis of differences in ecophysiological mechanisms for coping with reduced water availability between species and ploidy levels. All species/types displayed variation in drought stress tolerance, which confirms that there is sufficient variation for selection within these groups of grasses. Our results confirmed the better drought tolerance potential of Festuca arundinacea, but also showed which Lolium perenne genotypes are more tolerant.

Comparative physiological and proteomic analysis indicates lower shock response to drought stress conditions in a self-pollinating perennial ryegrass.

We investigated the physiological and proteomic changes in the leaves of three Lolium perenne genotypes, one Iranian putative self-pollinating genotype named S10 and two commercial genotypes of Vigor and Speedy, subjected to drought stress conditions. The results of this study indeed showed higher RWC (relative water content), SDW (shoot dry weight), proline, ABA (abscisic acid), nitrogen and amino acid contents, and antioxidant enzymes activities of S10 under drought stress in comparison with the two other genotypes. A total of 915 proteins were identified using liquid chromatography-mass spectrometry (LC/MS) analysis, and the number of differentially abundant proteins between normal and stress conditions was 467, 456, and 99 in Vigor, Speedy, and S10, respectively. Proteins involved in carbon and energy metabolism, photosynthesis, TCA cycle, redox, and transport categories were up-regulated in the two commercial genotypes. We also found that some protein inductions, including those involved in amino acid and ABA metabolisms, aquaporin, HSPs, photorespiration, and increases in the abundance of antioxidant enzymes, are essential responses of the two commercial genotypes to drought stress. In contrast, we observed only slight changes in the protein profile of the S10 genotype under drought stress. Higher homozygosity due to self-pollination in the genetic background of the S10 genotype may have led to a lower variation in response to drought stress conditions.

Can endosymbiotic microbes modulate natural selection in plant populations? An example with Lolium perenne and its fungal endophyte

Many plant species are symbiotic with systemic microbes. For example, many grasses are inhabited by fungal endophytes that affect aspects of their host’s physiology, morphology, and reproduction. However, there have not been any analyses of the potential effect of endophytes on the strength of phenotypic selection on quantitative traits. Here, a previously published data set on several life history traits measured for two years in a field population of 12–13 Lolium perenne genotypes, each replicated as symbiotic and non-symbiotic plants, was analyzed using the standard Lande-Arnold method of selection analysis. In one year, endophytic symbionts reduced the strength of selection on the number of reproductive tillers when relative fitness was expressed as seed yield. Also, symbionts selected for reduced tiller production when fitness was expressed as mean seed mass. These changes in the strength of selection only occurred when fitness of genotypes when symbiotic was unrelated to fitness of the same genotypes when non-symbiotic. In a second year, when fitness of symbiotic and non-symbiotic groups were significantly correlated, there was no detectable selection on reproductive tiller production. Because the effects of microbial endosymbionts were only shown for one year in a single host population, additional research is needed to better assess how endosymbionts might mediate selective pressures in other natural plant populations.

Enhanced expression of Rubisco activase splicing variants differentially affects Rubisco activity during low temperature treatment in Lolium perenne

Alternative splicing of the Rubisco activase gene was shown to be a point for optimization of photosynthetic carbon assimilation. It can be expected to be a stress-regulated event that depends on plant freezing tolerance. The aim of the study was to examine the relationships among Rubisco activity, the expression of two Rubisco activase splicing variants and photoacclimation to low temperature. The experiment was performed on two Lolium perenne genotypes with contrasting levels of freezing tolerance. The study investigated the effect of pre-hardening (15°C) and cold acclimation (4°C) on net photosynthesis, photosystem II photochemical activity, Rubisco activity and the expression of two splicing variants of the Rubisco activase gene. The results showed an induction of Rubisco activity at both 15°C and 4°C only in a highly freezing-tolerant genotype. The enhanced Rubisco activity after pre-hardening corresponded to increased expression of the splicing variant representing the large isoform, while the increase in Rubisco activity during cold acclimation was due to the activation of both transcript variants. These boosts in Rubisco activity also corresponded to an activation of non-photochemical mechanism of photoacclimation induced at low temperature exclusively in the highly freezing-tolerant genotype.In conclusion, enhanced expression of Rubisco activase splicing variants caused an increase in Rubisco activity during pre-hardening and cold acclimation in the more freezing-tolerant Lolium perenne genotype. The induction of the transcript variant representing the large isoform may be an important element of increasing the carbon assimilation rate supporting the photochemical mechanism of photosynthetic acclimation to cold.

Different photosynthetic acclimation mechanisms are activated under waterlogging in two contrasting Lolium perenne genotypes.

Increased precipitation and snowmelt during warmer winters may lead to low-temperature waterlogging of plants. Perennial ryegrass (Lolium perenne L.) is one of the most important cool-season grasses in agriculture. It is well adapted to cold climates, and may be considered as a model system for studying the mechanisms involved in cold acclimation. The aim of this study was to evaluate the effects of waterlogging on photosynthetic acclimation to cold in perennial ryegrass. Two L. perenne genotypes that differ in their responses to waterlogging in terms of freezing tolerance were compared. We evaluated the effects of waterlogging during cold acclimation on the water-soluble carbohydrate concentration, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity, photochemical efficiency of PSII, and transcript levels of the Rubisco activase (RcaA) and sucrose-sucrose fructosyltransferase (1-SST) genes. The genotype that did not accumulate water-soluble carbohydrates in the leaf under waterlogging showed a lower degree of feedback inhibition of photosynthesis under low temperature, and activated a photochemical mechanism of photosynthetic acclimation to cold. The other genotype accumulated water-soluble carbohydrates in the leaf during waterlogging, and activated a non-photochemical mechanism under cold conditions. Different photosynthetic acclimation systems to cold under waterlogging may be activated in these two contrasting L. perenne genotypes.

Metabolite profiling during cold acclimation of Lolium perenne genotypes distinct in the level of frost tolerance.

Abiotic stresses, including low temperature, can significantly reduce plant yielding. The knowledge on the molecular basis of stress tolerance could help to improve its level in species of relatively high importance to agriculture. Unfortunately, the complex research performed so far mainly on model species and also, to some extent, on cereals does not fully cover the demands of other agricultural plants of temperate climate, including forage grasses. Two Lolium perenne (perennial ryegrass) genotypes with contrasting levels of frost tolerance, the high frost tolerant (HFT) and the low frost tolerant (LFT) genotypes, were selected for comparative metabolomic research. The work focused on the analysis of leaf metabolite accumulation before and after seven separate time points of cold acclimation. Gas chromatography-mass spectrometry (GC/MS) was used to identify amino acids (alanine, proline, glycine, glutamic and aspartic acid, serine, lysine and asparagine), carbohydrates (fructose, glucose, sucrose, raffinose and trehalose) and their derivatives (mannitol, sorbitol and inositol) accumulated in leaves in low temperature. The observed differences in the level of frost tolerance between the analysed genotypes could be partially due to the time point of cold acclimation at which the accumulation level of crucial metabolite started to increase. In the HFT genotype, earlier accumulation was observed for proline and asparagine. The increased amounts of alanine, glutamic and aspartic acids, and asparagine during cold acclimation could be involved in the regulation of photosynthesis intensity in L. perenne. Among the analysed carbohydrates, only raffinose revealed a significant association with the acclimation process in this species.

Enhanced Expression of Rubisco Activase Confers to Increase in Rubisco Activity During Cold Acclimation in Lolium Perenne

Photosynthetic apparatus acclimation to low temperature is a prerequisite for proper hardening and acquired freezing tolerance. It has been shown that Lolium perenne plants have two isoforms of Rubisco activase, products of two splicing variants (RcaA1, RcaA2) of common pre-mRNA (Jurczyk et al., 2015). The aim of the study was to determine the relationship between the activation of mechanisms of photosynthetic acclimation to cold, the Rubisco activity and the expression of alternatively spliced Rubisco activase isoforms in Lolium perenne. Transcript levels of alternatively spliced mRNAs coding for two Rubisco activase isoforms were measured using real-time PCR. Rubisco activity has been determined spectrophotometrically. The measurements of chlorophyll-a fluorescence parameters, including photochemical and non-photochemical quenching, were made with a FMS2 fluorymeter. Gas exchange measurements were performed using an infrared gas analyser. All measurements were taken before cold acclimation, after 2 weeks of prehardening, and after 1 and 3 weeks of cold acclimation in two Lolium perenne genotypes with contrasting levels of freezing tolerance. In more freezing tolerant genotype the Rubisco activity was higher in treated plants relative to control. The increased Rubisco activity during cold acclimation was due to higher expression of both transcripts variants, representing two isoforms of Rubisco activase, but the shorter isoform seemed to be more active. The photochemical, but also non-photochemical mechanism of photosynthetic activation to cold has been activated in freezing tolerant genotype. It may be concluded that the increase in photochemical mechanism of photosynthetic acclimation to cold observed in Lolium perenne may be attributed to enhanced expression of Rubisco activase leading to increased Rubisco activity.The research was supported under a project DEC-2011/03/B/NZ2/00536 “The role of alternate mRNA splicing of Rubisco activase gene in acclimation of photosynthetic apparatus to cold” financed by the Polish National Research Centre.

Competitive outcomes depend on host genotype, but not clavicipitaceous fungal endophytes, in Lolium perenne (Poaceae).

• Cool-season grasses infected by endophytic fungal symbionts sometimes show improved tolerance of herbivory and abiotic stresses, but the potential effects of endophytes on host competitive ability are unclear. This study examined intraspecific competition among variable genotypes of Lolium perenne with and without the endophyte Epichloë festucae var. lolii (Clavicipitaceae, Ascomycota) to assess the effect of infection on competitive outcomes.• Eleven host genotypes distributed among infected plants of four cultivars of L. perenne were used for two pairwise competition experiments. In the greenhouse, an infected or uninfected ramet of each genotype was grown alone and paired in competition with a ramet of an uninfected genotype of a native accession of L. perenne. Tiller numbers and root and shoot dry mass were determined for targets and competitor plants after 15 wk.• Competition and host genotype had highly significant effects on all measured variables. However, endophyte-mediated effects on hosts were minor, and those that occurred depended on genotype. In addition, endophytic status of target plants did not influence tiller number or dry mass in 10 of 11 competitor genotypes, although these native genotypes did significantly vary in their competitive performance.• Genotypic variation among cultivars and accessions from native populations of L. perenne determines the effect of both intraspecific competition and infection by a fungal endophyte. However, in the absence of herbivory, asexual clavicipitaceous endophytes may not be as important to host success in competitive environments as previously thought in this globally important grass species.

Tetraploid Lolium Perenne genotypes Identified in Danish Semi-Natural Habitats

Tetraploid Lolium Perenne genotypes Identified in Danish Semi-Natural Habitats Christian Damgaard, Vibeke Simonsen, Jesper Givskov Sørensen, Thomas Didion, Marianne Bruus Abstract The ploidy of perennial ryegrass, Lolium perenne, was studied in order to assess the potential of tetraploidity as a means of preventing transgenes from spreading to natural populations.In contradiction to earlier observations, we found that tetraploid L. perenne genotypes was present in a semi-natural habitat in non-trivial proportions. Consequently, we conclude that tetraploidy will not prevent GM traits from spreading to natural rye grass populations by either an invasion or an introgression pathway. Full Text: PDF DOI: 10.15640/aijb.v2n3-4a2

Orthology Guided Assembly in highly heterozygous crops: creating a reference transcriptome to uncover genetic diversity in Lolium perenne

Despite current advances in next-generation sequencing data analysis procedures, de novo assembly of a reference sequence required for SNP discovery and expression analysis is still a major challenge in genetically uncharacterized, highly heterozygous species. High levels of polymorphism inherent to outbreeding crop species hamper De Bruijn Graph-based de novo assembly algorithms, causing transcript fragmentation and the redundant assembly of allelic contigs. If multiple genotypes are sequenced to study genetic diversity, primary de novo assembly is best performed per genotype to limit the level of polymorphism and avoid transcript fragmentation. Here, we propose an Orthology Guided Assembly procedure that first uses sequence similarity (tBLASTn) to proteins of a model species to select allelic and fragmented contigs from all genotypes and then performs CAP3 clustering on a gene-by-gene basis. Thus, we simultaneously annotate putative orthologues for each protein of the model species, resolve allelic redundancy and fragmentation and create a de novo transcript sequence representing the consensus of all alleles present in the sequenced genotypes. We demonstrate the procedure using RNA-seq data from 14 genotypes of Lolium perenne to generate a reference transcriptome for gene discovery and translational research, to reveal the transcriptome-wide distribution and density of SNPs in an outbreeding crop and to illustrate the effect of polymorphisms on the assembly procedure. The results presented here illustrate that constructing a non-redundant reference sequence is essential for comparative genomics, orthology-based annotation and candidate gene selection but also for read mapping and subsequent polymorphism discovery and/or read count-based gene expression analysis.

Frequency, type, and distribution of EST-SSRs from three genotypes of Lolium perenne, and their conservation across orthologous sequences of Festuca arundinacea, Brachypodium distachyon, and Oryza sativa

BackgroundSimple sequence repeat (SSR) markers are highly informative and widely used for genetic and breeding studies in several plant species. They are used for cultivar identification, variety protection, as anchor markers in genetic mapping, and in marker-assisted breeding. Currently, a limited number of SSR markers are publicly available for perennial ryegrass (Lolium perenne). We report on the exploitation of a comprehensive EST collection in L. perenne for SSR identification. The objectives of this study were 1) to analyse the frequency, type, and distribution of SSR motifs in ESTs derived from three genotypes of L. perenne, 2) to perform a comparative analysis of SSR motif polymorphisms between allelic sequences, 3) to conduct a comparative analysis of SSR motif polymorphisms between orthologous sequences of L. perenne, Festuca arundinacea, Brachypodium distachyon, and O. sativa, 4) to identify functionally associated EST-SSR markers for application in comparative genomics and breeding.ResultsFrom 25,744 ESTs, representing 8.53 megabases of nucleotide information from three genotypes of L. perenne, 1,458 ESTs (5.7%) contained one or more SSRs. Of these SSRs, 955 (3.7%) were non-redundant. Tri-nucleotide repeats were the most abundant type of repeats followed by di- and tetra-nucleotide repeats. The EST-SSRs from the three genotypes were analysed for allelic- and/or genotypic SSR motif polymorphisms. Most of the SSR motifs (97.7%) showed no polymorphisms, whereas 22 EST-SSRs showed allelic- and/or genotypic polymorphisms. All polymorphisms identified were changes in the number of repeat units. Comparative analysis of the L. perenne EST-SSRs with sequences of Festuca arundinacea, Brachypodium distachyon, and Oryza sativa identified 19 clusters of orthologous sequences between these four species. Analysis of the clusters showed that the SSR motif generally is conserved in the closely related species F. arundinacea, but often differs in length of the SSR motif. In contrast, SSR motifs are often lost in the more distant related species B. distachyon and O. sativa.ConclusionThe results indicate that the L. perenne EST-SSR markers are a valuable resource for genetic mapping, as well as evaluation of co-location between QTLs and functionally associated markers.

Costs of fungal endophyte infection in Lolium perenne genotypes from Eurasia and North Africa under extreme resource limitation

The effects of asexual, leaf-inhabiting endophytes on the growth of Lolium perenne are notoriously inconsistent and appear to be contingent on environmental conditions and host genetics. Both positive and negative growth effects of endophytes have been documented in some forage crop cultivars. Because they utilize host photosynthates, it is hypothesized that endophytes would impart a growth cost to infected plants under extreme resource limitation. The potential costs of infection by the fungal endophyte Neotyphodium lolii to its host grass, L. perenne, were investigated in accessions from Italy, Turkey, Morocco and Tunisia, the native part of the host's range. Four to five infected (+E) genotypes of L. perenne per accession were cloned into ramets, and the endophyte exterminated from half of the ramets (−E). Six +E and six −E ramets per genotype were grown for 5 months in a nutrient-poor substrate (vermiculite) within temperature- and light-controlled growth chambers. Accession and genotype within accession affected dry mass. Endophyte infection significantly reduced root:shoot ratio and the proportion of the shoot that was alive and photosynthetic. Relative interaction intensity indexes were negative for most genotypes, indicating host–endophyte associations were mostly parasitic. However, there were significant infection by genotype interactions; thus, endophyte-mediated effects depend on particular host genotype–endophyte combinations. This research is one of the few that have documented costs to endophyte infection in a grass–endophyte symbiosis. This cost, manifested as reduced root:shoot ratio and photosynthetic shoot fraction, was evident for infected L. perenne growing under conditions of extremely poor substrate nutrient availability.

Effects of biotic and abiotic stress on the growth of three genotypes of Lolium perenne with and without infection by the fungal endophyte Neotyphodium lolii

SummaryThe combinations of three genotypes of Lolium perenne with and without (i) infection by the fungal endophyte Neotyphodium lolii, (ii) infection by ryegrass mosaic virus and (iii) one of five different forms of abiotic stress were studied in pot experiments in a glasshouse. The five abiotic stress treatments were (i) low pH (compared with ‘optimal’ pH), (ii) cutting plants to a height of 1 cm (compared with 5 cm), (iii) shading (compared with no shading), (iv) cutting plants at 2‐weekly intervals (compared with 6 wk) and (v) low nitrogen applied (compared with ‘high’ nitrogen applied). On average, over the five experiments, the accumulated herbage dry weight was 10% more for N. lolii‐infected plants than uninfected, 22% more for virus‐free plants than infected, and 265% more for ‘unstressed’ plants than for plants with abiotic stress. The effects of N. lolii infection on plant growth when the plants were under abiotic or biotic stress were not consistent.

Differences in growth and nitrogen productivity between a stay-green genotype and a wild-type of Lolium perenne under limiting relative addition rates of nitrate supply.

The stay-green mutation of the nuclear gene sid inhibits chlorophyll degradation during leaf senescence in grasses. Decreased productivity is expected under conditions of limited external N availability, due to the higher retention of N in senescent tissues. However, this has not been reported when plants are grown at limiting low external concentrations of N. In the present study a different approach was taken, based on the relative addition rate method for defining limiting N supply. Wild-type and stay-green genotypes of Lolium perenne L. were grown for 30 days in flowing solution culture and then supplied with NO3- on an hourly basis over 35 days at relative addition rates (RARs) of 0.03, 0.06, 0.09 and 0.12 day-1, ranging from severe N limitation to optimal supply. Plants were steady-state labelled with 15NO3- prior to RAR treatments, then switched to 14NO3- to allow measurement of the re-distribution of N absorbed prior to RAR control. Following acclimation, relative growth rates (RGRs) approached the corresponding RAR, but were significantly lower for stay-green than wild-type at RARs of 0.03 and 0.06 day-1. Tiller numbers were lower in stay-green plants after 35 days at all RARs except 0.12 day-1. Concentrations of total N in senescent laminae of stay-green plants exceeded those in wild-type plants by a similar margin (4.8-6.8 mg g-1 DW) irrespective of RAR. Maximum nitrogen productivity (Pn) was 3.9 g DW g-1 N day-1 (Nmin = 7.1 mg g-1 DW) in wild-type plants, and 5.1 g DW g-1 N day-1 (Nmin = 10.7 mg g-1 DW) in stay-green plants. The higher N productivity of stay-green plants indicated these plants used a smaller pool of metabolically available N more efficiently in biosynthesis compared with wild-type plants. The retention of N, absorbed prior to RAR treatments, in senescent laminae was significantly higher in stay-green plants at RAR of 0.03 day-1 after day 21 (i.e. 20% versus 15% of the total N recovered). However, in terms of the whole N economy of the plant the margin represented only 1.7% of the total N content on day 35.

Tracing of 2n egg occurrence in perennial ryegrass (Lolium perenne L.) using interploidy crosses

Several genotypes of Lolium perenne (2n = 2x = 14) were screenedfor the production of 2n eggs. In each cross a diploid genotype, used asfemale parent, was pollinated with a tetraploid genotype. All interploidycrosses were made in isolation cages. Flow cytometrical analysis of theprogeny of 154 diploid plants revealed 28 tetraploid descendants. Theseoffspring plants were harvested on 15 different diploid mother plants.Amplified Fragment Length Polymorphism (AFLP) markers were used tocheck the parenthood of these tetraploids. Two seedlings died, theremaining plants could, after AFLP fingerprinting, be identified as meiotictetraploids. The results obtained allowed to conclude that the tetraploidprogeny plants harvested on 15 diploid mother plants were the result ofthe fertilisation of an unreduced egg by a reduced pollen grain of thetetraploid plant.

Effect of drought on the growth of Lolium perenne genotypes with and without fungal endophytes

Abstract Grass leaves are often inhabited by fungal endophytes that can enhance host growth. In some forage species, endophytes improve host resistance to, and recovery from, drought. Our objective was to determine if the growth of genotypes of Lolium perenne L. was improved by endophytes during recovery from drought. Thirteen infected genotypes were cloned into ramets. Half were treated with a systemic fungicide to eliminate the endophyte (E−); half were untreated and retained high endophyte levels (E+). In a glasshouse, half of all E− and E+ ramets were watered regularly, whilst half were exposed to a 2 week drought on two occasions, each followed by a 3 week recovery period. After the first drought and recovery period, endophytes significantly reduced tiller production in the drought‐stressed group. After the second drought and recovery period, effects of drought on live leaf area and dry mass were highly dependent on host genotype, but not endophytes. The mean tiller mass of E+ ramets after drought was significantly less than that of watered E+ ramets, but this was not true in E− ramets. For six genotypes there was greater mass allocation to storage in the tiller bases of E− ramets after drought. This perennial ryegrass population showed marked genotypic variation in the ability to recover from drought stress, but endophytes played little or no role in this ability. For some host genotypes there may be a metabolic cost of harbouring endophytes during environmentally stressful conditions.

Genotypic variation in the regrowth of Lolium perenne following clipping: effects of nutrients and endophytic fungi

1. The objective of this research was to determine the extent to which regrowth rate after clipping and the specific leaf area (SLA) of genotypes of Lolium perenne were influenced by soil nutrients and endophytic fungi. 2. Twelve infected genotypes were cloned into ramets. Half were treated with a systemic fungicide that greatly reduced endophyte levels; half were untreated and retained high endophyte levels. Ramets of each genotype were subjected to low, medium or high levels of nutrients in a glasshouse for 11 weeks. 3. Plants were clipped at soil level at 11 weeks, allowed to regrow for 14 weeks and clipped again. SLA was determined at 11 and 25 weeks. Regrowth rate was calculated based on changes in leaf area and leaf dry mass between 11 and 25 weeks. 4. As a main effect, endophytes had no influence on regrowth rates and mean endophyte levels, as measured by hyphal counts within the leaves of five genotypes at high and low nutrients, were not correlated with regrowth rates. However, after clipping, regrowth responses to soil nutrients and endophytes were genotype‐specific. Some genotypes in the high endophyte group showed an enhancement of regrowth, whilst others showed no response or a depressive effect of endophytes. 5. At the time of leaf clipping, SLA was significantly affected by genotype, nutrients and endophytes. At medium nutrients, the SLA of high endophyte plants was significantly lower than that of low endophyte plants. However, the SLA of the regrowth was affected by nutrients but not endophytes. Mean endophyte levels, as measured by hyphal counts within the leaves of five genotypes at high and low nutrients, were not correlated with SLA at 11 or 25 weeks. 6. For both high and low endophyte plants, regrowth rate was negatively correlated with SLA. 7. Perennial ryegrass possesses genotypic variation in the ability to regrow following defoliation and this ability is conditioned by abiotic (nutrients) and biotic (endophyte) factors.

Co-adaptation between neighbours? A case study with Lolium perenne genotypes

Co-adaptation between neighbouring genotypes of Lolium perenne was examined in a pot experiment over an 18 month period. Competitive interactions in pure and mixed stands were examined using 9 genotype pairs (established as neighbours from electrophoresis data), 7 from a 10 year-old, and 2 from a 40+ year-old pasture. Combinations of each pair of neighbours grown together, and each grown with 5 randomly chosen alien (non-neighbour) genotypes sampled from the same pastures were also assessed. Seven harvests of green matter produced above 20 mm were made, and 50–135 kg N ha−1 was administered after each harvest. Data for dry weight at each harvest for pure and mixed stands, and Relative Yield Totals (RYT) were obtained for neighbours and aliens in each treatment.

Influence of medium and cold pretreatment on androgenetic response in Lolium perenne L.

Genotypes of Lolium perenne L. with different androgenetic responses were used to test effects of induction medium composition. The media tested were potato II (pII), 190-2, and modified Linsmaier and Skoog media, LS-1, LS-2, and LS-3. The effect of different gelling agents, activated charcoal in a 'double layer' design, and casein hydrolysate were also studied. From 36,696 anthers, 25,906 embryo-like structures, 1,959 albino and 173 green plants were generated. Significant differences were found between media, genotypes and medium-genotype interactions studied. All three media commonly used, pII, 190-2, and LS-3, were equivalent in production of green plants. Cold pretreatment of the anthers (4°C) significantly increased the number of embryo-like structures, the number and proportion of albino plants produced, but not the production of green plants.