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.

The Leibniz Institute of Plant Genetics and Crop Plant Research maintains a diverse collection of wild potato germplasm with more than 2800 accessions from 139 botanical species, 19 Solanum series and 14 countries of origin. During the past two decades, almost half of the collection has been screened for resistance to late blight (Phytophthora infestans) and pale cyst nematode (Globodera pallida (Pa2/3)) infection under laboratory conditions. In particular, resistance to tuber blight was considered, which is an important component of P. infestans resistance and has not been investigated that detailed yet. Out of the 1055 accessions tested, 68 were very resistant and 311 were classified as partially resistant against tuber blight. Besides in accessions of species well-known for foliage resistance, resistance to tuber blight was also observed in previously less reported species such as S. acaule, S. fendleri, S. megistacrolobum, S. polytrichon, S. jamesii, S. trifidum, and S. tarnii. In regard to G. pallida infection, 78 out of 749 tested accessions were classified as resistant, belonging to the species S. acaule, S. circaeifolium, S. gourlayi, S. kurtzianum, S. oplocense, S. sparsipilum, S. spegazzini and S. vernei. New or previously less reported sources of G. pallida resistance were identified in accessions of S. brevicaule, S. demissum and S. microdontum. In various accessions of different species, combined resistance was observed and the relationship to their country of origin is discussed.

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.

Perennial ryegrass (Lolium perenne L.) is increasingly important as a forage grass in the Nordic and Baltic region, especially in the light of climate change. However, winter hardiness and persistence need to be improved. This article describes the long-term Nordic/Baltic public-private partnership for pre-breeding in perennial ryegrass, started in 2012. The basis for the project is detailed genotyping and phenotyping of nearly 400 genebank accessions, followed by generation of new broad-based diploid and tetraploid breeding populations, locally adapted and trait-based populations. Preliminary results confirm the need for more robust and stable cultivars with wider adaptations, and genebank accessions need to be introgressed and recombined with adapted materials followed by natural/artificial selection in order to create novel germplasm for these regions.

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.

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.

Lolium grasses are widely distributed and used, and their economic importance is significant. We report the development of Lolium single nucleotide polymorphism (SNP) markers that were derived from barley EST data and that were suitable for allele quantification (AQ) via pyrosequencing (PSQ). Polymorphism information content (PIC) values for 22 developed markers ranged between 0.23 and 0.93 (average PIC value 0.80). The markers were used to characterize a collection of 2829 Lolium accessions. Eleven SNP markers could be mapped in the Lolium perenne VrnA mapping population. This is the first report on fingerprinting a comprehensive genebank collection by quantification of SNP alleles. The markers clearly distinguish between L. perenne and L. multiflorum and will prove as very useful for the management of germplasm collections.

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).

At IPK, routine application of cryopreservation started in the year 1998 on potato and garlic and, in 2006, on mint. Allium pollen is the newest target. Main methods are: DMSO droplet freezing in potato, vitrification in garlic, droplet vitrification in mint, and direct cooling of pollen in Allium. Across the years, some changes in detailed protocol steps were introduced improving the methods. Since more than 25 years, accessions of IPK's Potato Collections have been maintained via in vitro culture. For potato, a protocol including microtuber formation was applied since the beginning with only minimal modifications. Garlic, however, is not amenable to in vitro storage over such long periods and quickly declining quality requires using fresh material. Accumulating endophytic colonisation revealed to be the main obstacle for prolonged use of in vitro plantlets as source for cryopreservation. Further investigations were performed on morphogenesis, tissue water conditions and genetic stability. For potato, studies were conducted analyzing the methylation patterns of different potato cultivars under three different maintenance systems (field, in vitro, in cryo) in 2012. Although this study revealed differences in the methylation status of different single plants of the same genotype these differences could not be traced back to one maintenance system in particular. Hence, it can be stated that in cryo maintenance does not induce additional genetic variation. In mint, no differences between the in vitro source plants and regenerants from cryopreservation were found using RAPDs. Cost estimations were done in potato and garlic. With respect to cost factors, the large potato collection had been prioritized depending on the request frequency so far experienced for the various genetic resources.

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.

Contrasting hypotheses exist about the relationship between plant species diversity and genetic diversity. However, experimental data of species diversity effects on genetic differentiation among populations are lacking. To address this, Lolium perenne was sown with an equal number of seeds in 78 experimental grasslands (Jena Experiment) varying in species richness (1, 2, 4, 8 to 16) and functional group richness and composition (1-4; grasses, legumes, small herbs, tall herbs). Population sizes were determined 4 years after sowing, and single-nucleotide polymorphism (SNP) DNA markers based on bulk samples of up to 100 individuals per population were applied. Genetic distances between the field populations and the initially sown seed population increased with sown species richness. The degree of genetic differentiation from the original seed population was largely explained by actual population sizes, which suggests that genetic drift was the main driver of differentiation. Weak relationships among relative allele frequencies and species diversity or actual population sizes, and a positive correlation between actual population sizes and expected heterozygosity also supported the role of genetic drift. Functional composition had additional effects on genetic differentiation of L. perenne populations, indicating a selection because of genotype-specific interactions with other species. Our study supports that genetic diversity is likely to be lower in plant communities with a higher number of interspecific competitors. Negative effects of species richness on population sizes may increase the probability of genetic drift, and selection because of genotype-specific interactions depending on species and genotypic community composition may modulate this relationship.

Genetic variation inLactuca serriola, the closest wild relative of cultivated lettuce, was studied across Europe from the Czech Republic to the United Kingdom, using three molecular marker systems, simple sequence repeat (SSR, microsatellites), AFLP and nucleotide-binding site (NBS) profiling. The ‘functional’ marker system NBS profiling, targeting disease resistance genes of the NBS/LRR family, did not show marked differences in genetic diversity parameters to the other systems. The autogamy of the species resulted in low observed heterozygosity and high population differentiation. Intra-population variation ranged from complete homogeneity to nearly complete heterogeneity. The highest genetic diversity was found in central Europe. The SSR results were compared to SSR variation screened earlier in the lettuce collection of the Centre for Genetic Resources, the Netherlands (CGN). In the UK, practically only a single SSR genotype was found. This genotype together with a few other common SSR genotypes comprised a large part of the plants sampled on the continent. Among the ten most frequent SSR genotypes observed, eight were already present in the CGN collection. Overall, the CGN collection appears to already have a fair representation of genetic variation from NW Europe. The results are discussed in relation to sampling strategies for improving genebank collections of crop wild relatives.

Germplasm accessions of wildLactucaspecies are maintained worldwide inex situcollections as gene reservoirs for quality and disease resistance traits for cultivated lettuce. Accessions of 12Lactucaspecies from 6 genebanks were compared via morphological characterization and AFLP (Amplified Fragment Length Polymorphism)-based profiling to estimate the extent of duplication. A method of assessing redundancy within very similar, but not identical accessions, is proposed, based on 352 polymorphic AFLP products. Seven duplication groups showed a high level of AFLP similarity, and one pair ofLactuca salignaaccessions displayed identical AFLP profiles. In several cases, the morphological assessment indicated that a taxonomic reclassification of accessions was necessary. Candidate duplicates were identified using population parameters and inter- and intra-accession variability. The implications of these findings on the conservation of wild species are discussed.

Expeditions were conducted in the Czech Republic, Germany, the Netherlands and United Kingdom in 2001 (partly 1998) to study Lactuca serriola L. (prickly lettuce, compass plant) geographic distribution, ecology, habitat characteristics and occurrence of diseases and pests on this species. During these missions the seed material of L. serriola L. was collected in an east–west transect of these four countries. The European transect where seeds were collected and field observations were made represents a relatively large area between 2°34′50′′ W–17°32′46′′ E and 47°40′42′′–54°04′19′′ N. The seed material was used for regeneration, inclusion in the national genetic resources collections of individual countries and for research purposes in follow-up studies. During the missions, 50 locations with occurrence of L. serriola L. were visited (16 in Czech Republic and Germany, 10 in UK and 8 in the Netherlands). Individual seed lots of sixteen different plants were collected at each location (L. serriola L. population). Thus, in total 800 seed samples were collected. In Czech Republic and Germany L. serriola L. f. serriola dominated in all observed populations, in the Netherlands both f. serriola and f. integrifolia occurred in pure or mixed stands, whereas in the United Kingdom L. serriola L. f. integrifolia (S.F. Gray) S.D. Prince et R.N. Carter was dominant. L. serriola L. was recorded at various altitudes (−4 to 410 m), different habitats (ditches, along roads, fields and field margins, ruderal places, pavements and parking sites, fallow fields), individual populations varied substantially in size (20 to >1000 plants), area covered (25–10,000 m2), and the structure and character of associated plant communities. Natural infections by downy mildew (Bremia lactucae Regel) and powdery mildew (Golovinomyces cichoracearum (DC.) V.P. Gelyuta) were observed in some populations. B. lactucae Regel was recorded only in Czech Republic, G. cichoracearum (DC.) V.P. Gelyuta was more common in continental Europe. General and specific aspects of L. serriola L. geographic distribution and ecology are discussed.

The work of this GENRES CT99 109-112 project has been supported by the European Commission in the framework of Council Regulation (EC) No 1467/94 and by the partner national programmes.