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.

Interspecific and intergeneric hybridization within the Festuca-Lolium complex is frequently used in forage plant breeding. However, little is known about the natural occurrence and competitiveness of such hybrids. We collected naturally formed hybrids between Festuca apennina, Festuca pratensis, and Lolium perenne in different habitats of Switzerland and the British Isles and studied their origin, the ease of their spontaneous formation, and their competitiveness with parental species. A special attention was paid to the largely sterile triploid forms and their rare sexual progeny. The triploid hybrid F. apennina × F. pratensis proved to be widespread and often highly competitive in Swiss permanent pastures. The majority of these hybrids originated from F. apennina as the seed parent although little or no F. apennina grew nearby. In an experimental setting with ample F. pratensis pollen provided by neighbouring plants, up to 20 % of seeds from open pollinated F. apennina plants were interspecific hybrids; among seeds collected in natural habitats, only 0.35 % were hybrids. At an experimental site at 1 000 m altitude, these triploid hybrids grew much more vigorously than corresponding tetraploid pure F. apennina, confirming their great competitiveness at such altitudes in permanent grasslands. The triploid hybrids were only marginally fertile suggesting that vegetative propagation by rhizomes is the cause of their competitive success in grassland. Moreover, triploid progeny retained the chromosome constitution of their mother plants indicating the possibility of apomixis. Natural triploid F. pratensis × L. perenne hybrids were partially female fertile (a seed set of 0.1 % or less) whereas diploid hybrids did not produce any viable seeds. Progenies of these triploids showed considerable chromosome alterations, such as loss of a genome or recombination due to homoeologous pairing, and only rarely the chromosome constitution of the triploid mother plant was retained. It was concluded that natural triploid interspecific hybrids could expand the range of their progenitor species and might function as bridges transferring genes between them.

Funding information German Federal Ministry of Food and Agriculture Program: “F€ orderung von Innovationen zur Z€ uchtung klimaangepasster Kulturpflanzen im Rahmen des Programms zur Innovationsf€ orderung”, Grant/Award Number: FKZ: 313-06.01-28-1-45.030-10 (IPK), FKZ: 511-06.01-28-1-45.029-10 (LfL), FKZ: 511-06.01-28-1-45.031-10 (JKI) Abstract The objectives of this research were to establish a practicable phenotyping platform for assessing the drought stress response of perennial ryegrass (Lolium perenne L.; Lp), and to use this platform for evaluating the variation for drought tolerance among a panel of 39 diverse Lp populations. A moderate-to-strong correlation was assessed between the performance of plants grown in a hydroponics system, where the stress was generated by the addition of polyethylene glycol (PEG), and those grown in the field in a rainout shelter. Following the application of drought stress, tetraploid Lp populations, along with a small number of reference Festulolium and Festuca sp. accessions, were able to develop more shoot and root dry matter than diploid Lp populations. The onset of drought symptoms was also delayed within these accessions and the plants recovered better once drought had been relieved. Although most of the diploid Lp populations were drought susceptible, there was a considerable accession-to-accession variation for performance under drought stress conditions. Measuring biomass production and post-drought recovery in rainout shelter experiments in combination with the assessment of root biomass accumulation in PEG-supplemented hydroponics represented a viable means of screening Lp germplasm for drought tolerance.

The ecotypic diversity of perennial ryegrass (Lolium perenne L.) is a major genetic resource for breeding programs. In three replicated micro-sward trials in France, Belgium and Germany, we measured spring growth and recorded heading date of round 400 genebank accessions from the natural diversity of L. perenne that were selected as to represent the wide range of variability in this species. We observed marked differences between trial locations as well as interaction between accessions and locations in the timing of spring growth rates along growing-degree-days (GDDs). These preliminary results are part of a wider project aiming to investigate the natural adaptation of perennial ryegrass to various regional climates across its spontaneous area of presence in Europe.

Aim Grasslands have been pivotal in the development of herbivore breeding since the Neolithic and are still nowadays the most widespread agricultural land-use across Europe. However, it remains unclear whether the current large-scale genetic variation of plant species found in natural grasslands of Europe is the result of human activities or natural processes. Location Europe. Taxon Lolium perenne L (perennial ryegrass). Methods We reconstructed the phylogeographic history of L. perenne , a dominant grassland species, using 481 natural populations including 11 populations from closely related taxa. We combined the Genotyping-by-Sequencing (GBS) and Pool-sequencing (Pool-seq) methods to obtain high-quality allele frequency calls of ~ 500 k SNP loci. We performed genetic structure analyses and demographic reconstructions based on the site frequency spectrum (SFS). We additionally used the same genotyping protocol to assess the genomic diversity of a set of 32 cultivars representative of the L. perenne cultivars widely used for forage purposes. Results Expansion across Europe took place during the Würm glaciation (12-110 kya), a cooling period that decreased the dominance of trees in favour of grasses. Splits and admixtures in L. perenne fit historical sea level changes in the Mediterranean basin. The development of agriculture in Europe (7-3.5 kya), that caused an increase in the abundance of grasslands, did not have an effect on the demographic patterns of L. perenne . We found little differentiation between modern cultivars and certain natural variants. However, modern cultivars do not represent the wide genetic variation found in natural populations. Main conclusions Demographic events in L. perenne can be explained by the changing climatic conditions during the Pleistocene. Natural populations maintain a wide genomic variability at continental scale that has been underused by recent breeding activities. This variability constitutes valuable standing genetic variation for future adaptation of grasslands to climate change, safeguarding the agricultural services they provide.

Between 2002 and 2010, a total of 366 Lolium perenne L. genebank accessions originating from collection trips to Bulgaria, Croatia, Spain and Ireland were evaluated in field experiments together with commercial check varieties at the island of Poel in northern Germany. Ten plant parameters were visually scored, including the development before and after winter, spring growth, heading, plant biomass and the incidence of disease symptoms. The ecotypes collected in Croatia and Spain achieved high scores for all the growth parameters evaluated, particularly in the first and second experimental year, and were well comparable to the check varieties. The Bulgarian ecotypes exhibited a low plant biomass development after the first cut and before winter but a high productivity in spring and a low susceptibility to rust infection. The ecotypes from Ireland revealed a low aftermath heading in the second experimental year and a superior growth after winter in the third year. In conclusion, the L. perenne ecotypes studied showed a high variability regarding important agronomic attributes and several accessions were identified that exceeded the average performance of the check varieties.

Lolium perenne is one of the most important grass species in Europe and subject of intensive breeding and research. Hence, there is a substantial need for well described, diverse and easily available genetic resources. The Satellite Collections North of the IPK Genebank continuously characterize and evaluate genebank accessions of oil and fodder crops. As an example, results from characterization and evaluation trials of 336 L. perenne accessions collected in Bulgaria, Croatia, Ireland and Spain are presented. Traits considered were, amongst others, phenological development, ear emergence, biomass production, disease susceptibility and winter hardiness. Results from the three-year evaluation trials showed a high variability regarding these traits. Generally, the Spanish ecotypes revealed a high biomass production level, while the Bulgarian ecotypes were characterized by a low rust susceptibility. The Irish ecotypes showed a better growth after winter than the ecotypes from the other countries in the third scoring year. These results have been transferred to the in-house developed Genebank Information System (GBIS) and to the international EURISCO information system. Their access via EURISCO is demonstrated.

In 2013, the fifth EUCARPIA multisite rust evaluation trial took place. A set of 16 Italian (Lolium multiflorum), 4 hybrid (L. boucheanum) and 34 perennial ryegrass (L. perenne) cultivars were sown at 21 sites in 11 European countries. The cultivars were grown as rows in a completely randomized block design with four replicates. Rust incidence was scored in the year of seeding using a scale based on an estimation of the percentage of leaf area affected. Crown rust (Puccinia coronata f. sp. lolii) was the most frequently observed rust species. Compared to the previous trials, stem rust (P. graminis f. sp. graminicola) was reported more frequently, i.e., at eight sites for perennial ryegrass but also at five sites for Italian ryegrass. At most sites, there was a highly significant difference in crown and stem rust resistance among Italian and perennial ryegrass cultivars. The ranking of the Italian/hybrid and perennial ryegrass cultivars in terms of crown rust susceptibility was very consistent across the different sites. Moreover, the ranking of the mean crown and stem rust susceptibility of the cultivars was highly correlated with the corresponding ranking of the cultivars in the 2001, 2004, 2007 and 2010 trials, respectively. There is no evidence that crown and stem rust resistance of an individual cultivar was overcome by the rust pathogen over the 12 years of experimental observations.

Perennial ryegrass (Lolium perenne L.) is the most valued temperate grass species in Europe. Between 2002 and 2010, a total of 352 L. perenne accessions originating from four European countries (Bulgaria, Croatia, Ireland and Spain) were evaluated in four phenotyping experiments at the Malchow experimental station of the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK). Ten plant parameters were visually scored, including development before and after winter, spring growth, plant biomass and incidence of crown rust and disease symptoms (leaf spot symptoms). Accessions from Croatia, Ireland and Spain were characterized by higher plant biomass in the 2nd scoring year than Bulgarian accessions. Considering the incidence of rust and diseases in perennial ryegrass accessions, the present study showed that the variation for scored crown rust and disease symptoms was higher in Irish and Bulgarian accessions. Correspondence analysis (CA) was carried out to examine the relationship between scored traits and 352 L. perenne accessions. The results presented in this study provide a brief description of L. perenne accessions maintained at the Satellite Collections North of the IPK Genebank.

Global climate change is one of the biggest challenges for research in agricultural science. In Europe, expected temporary periods of reduced precipitation during the growing season will affect crop yields. Perennial ryegrass (Lolium perenne L.) is one of the most important forage grasses in Europe due to high yields and nutritional composition. Because perennial ryegrass has no distinct tolerance to drought, it is likely to be particularly affected by global climate change. Perennial ryegrass is found in many geographical regions across Europe, thus genetic variation for drought tolerance is likely. We have evaluated persistence under temporary drought conditions of 200 accessions, representing gene bank material from several countries with differing amounts of precipitation as well as breeding material. The evaluation was based on field trials at drought-prone locations. A contrasting drought response could be detected within the accessions and a representative subsample of 54 accessions could be identified for use in a two location rain-out shelter trial. Different methods for phenotyping recovery after drought stress were compared and traits were scored on a single plant basis in the semi-controlled environment rain-out shelter. A huge variation was found not only between, but also within accessions. It became obvious that the most important mechanism under Central European drought conditions is not maintenance of biomass production under severe drought stress but rather fast recovery after a limited period of water shortage. Single clones with contrasting recovery performance could be identified and will be used to investigate drought tolerance mechanisms and breed new varieties in future projects.

The IPK Genebank, Satellite Collections North, at Malchow/Poel is responsible for the ex situ maintenance of genetic resources of forage plants in Germany. More than 10,400 accessions of grasses (forage and turf species) and 1,300 small grained forage legumes (red clover and alfalfa) belong to the collections, originating mainly from Europe, but partially also from destinations around the world. The main goal is to hold all accessions available for distribution and characterize/evaluate them for different research and breeding purposes as intensively as possible. For this means, a good documentation system is necessary, besides the management of PGR according to European Genebank Standards and a protocol for a quality management system (certificate ISO 9001:2008).

Les graminees fourrageres font l’objet de programmes de selection depuis plusieurs decennies afin d’offrir des semences de haute valeur agronomique pour la creation de prairies temporaires. La diversite de ces especes presente dans les prairies naturelles a fourni le materiel genetique qui a permis d’initier les premiers programmes d’amelioration puis d’enrichir regulierement les pools de selection. Pour cela, des campagnes de collecte de diversite naturelle ont ete entreprises sur de vastes territoires. Nous montrons que la diversite naturelle des graminees fourrageres reste encore une ressource genetique importante, notamment dans l’objectif de repondre a de nouveaux enjeux agro-environnementaux. La distribution spatiale de cette diversite est esquissee a trois echelles geographiques (locale, regionale et continentale) et les modalites de sa collecte sont discutees. L’importance du maintien in situ de cette diversite naturelle est soulignee. Il est montre que les collections des centres de ressources genetiques peuvent fournir un support pour developper des modeles permettant d’evaluer les risques potentiels qui pesent sur le maintien in situ de la diversite naturelle. Ces differents points sont developpes en s’appuyant sur deux etudes de la diversite du ray-grass anglais, l’une a l’echelle locale, l’autre combinant les echelles regionale et continentale.

The EUCARPIA multi-site rust evaluation was repeated in 2010 for the fourth time. The trials were sown at 24 sites in 11 countries in Europe. The 20 Italian/Hybrid (Lolium multiflorum and L. boucheanum, respectively) and 34 perennial ryegrass (L. perenne) cultivars were sown in separate trials. The cultivars were grown as rows in a completely randomized block design with four replicates. Rust incidence was scored in the year of seeding by each of the participants. The method used to test cultivars for rust resistance was based on an estimation of the percentage of leaf area affected. Crown rust (Puccinia coronata f. sp. lolii) was again the most frequently observed rust on both ryegrass species. Stem rust (P. graminis f.sp. graminicola) was reported at only one site for Italian and at four sites for perennial ryegrass. Variation in resistance to crown rust among cultivars was significant at 17 sites for Italian and at 16 sites for perennial ryegrass. The cultivars ‘Tarandus’, ‘Gosia’, ‘Caballo’ and ‘Domino’ showed the highest level of resistance of all the Italian ryegrass cultivars tested. ‘Gwendal’ and ‘Bocage’ were the most crown rust resistant perennial ryegrass cultivars. The ranking of the mean crown rust susceptibility of the cultivars was highly correlated with the corresponding ranking of cultivars in the 2001, 2004 and 2007 trials, respectively. This was true for both perennial and Italian ryegrass. Coefficients of rank order correlations of average cultivar disease scores between the years were greater than rs = 0.97 (p < 0.05) for Italian and rs = 0.86 (p < 0.05) for perennial ryegrass, respectively. Therefore, there is no evidence that crown rust resistance of an individual cultivar was overcome by the rust pathogen over the 9 years of experimentation.

Late spring frost events can affect vegetation. The response of grassland species, however, is generally unknown. We explore the late-frost sensitivity of four common European grass species and investigate whether these species exhibit local adaptations to late frost on a continental scale and whether past climatic experience influences late frost sensitivity. Ecotypes of Arrhenatherum elatius, Alopecurus pratensis, Festuca pratensis, and Holcus lanatus from Spain, Italy, Bulgaria, Hungary, Sweden and Germany were exposed to late frost after drought and warming manipulations in the preceding growing season in a common garden experiment. Late frost reduced the productivity of the grasses on average by 20%. Ecotypes differed in their late-frost sensitivity in three of the four species and local adaptations to late frost were identified. Previous exposure to drought and warming caused differences in late-frost sensitivity in some cases. The impact of late frost events may increase in a warmer world due to an earlier onset of growing and no change in timing of late frost events. The history of climatic exposure can alter the performance of plants, possibly through epigenetic mechanisms. Based on the complex response pattern observed, a maximization of genetic diversity is proposed as a promising adaptation strategy against climate change.

The federal German ex-situ collection of agricultural and horticultural plants at the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK)—the IPK Genebank—with its headquarters in Gatersleben and a satellite collection for fodder crops at Malchow/Poel, is one of the most comprehensive plant genetic resources (PGR) collections worldwide. In addition to collection, conservation, documentation and distribution activities, the characterization and evaluation comprises a major part of the work at the IPK Genebank, particularly in field trials of collected material with common geographical origin or habitat. Evaluated traits of grasses include plant development before and after winter, growth type, length and width of flag leaf and plant height or resistance to diseases. We assessed Irish Lolium perenne accessions for relevant breeding traits to give an example of IPK Genebank activities. On the basis of the monitored traits we are able to predict the behavior of plants against abiotic stress (e.g. drought, late frost and winter hardiness), serving as a pre-selection instrument for different plant breeding objectives and strategies.

A set of 15 Italian (Lolium multiflorum), three hybrid (L. boucheanum) and 33 perennial ryegrass (L. perenne) cultivars were evaluated for their rust susceptibility in the field. The cultivars were grown in 2001, 2004 and 2007 at 29, 32 and 27 European sites, respectively. Rust incidence was scored during different growth cycles using a scale from one (no rust) to nine (susceptible). Crown rust (Puccinia coronata f. sp. lolii) was the most frequently observed rust species on Italian, hybrid and perennial ryegrass during all three experimental years. There was a highly significant difference in mean crown rust scores among Italian and perennial ryegrass cultivars, respectively, in each of the 3 years. The ranking of the cultivars was very consistent across the different sites within each year (with some exceptions), despite a significant interaction of cultivar response with sites. Moreover, the rank order correlations of mean cultivar rust scores were highly significant (r > 0.9) between the years. Stem rust (P. graminis f. sp. graminicola) occurred almost exclusively on perennial ryegrass. The cultivars showed significant variation in stem rust susceptibility. Rank order correlations of mean cultivar stem rust scores were mostly significant between sites within each year and highly significant between the years. The ranking of perennial ryegrass cultivars was different depending on whether crown or stem rust was scored. However, the rank order correlation between the mean disease scores of the cultivars for the two pathogens was low but still significant. At a particular site the assessment of crown or stem rust was in most cases very consistent over the period of experimentation. Therefore there was no evidence that rust resistance of an individual cultivar was overcome by the rust pathogen at a particular site over the 7 years of experimentation.

About 28% of agricultural land in Bulgaria is grassland that is mainly confined to foothills, intermediate mountain areas and alpine pastures and meadows