Swiss Mattenklee landraces, a distinct and diverse genetic resource of red clover (Trifolium pratense L.)

Genetic variability within and among 19 landraces and cultivars of red clover (Trifolium pratense L.) was investigated by means of amplified fragment length polymorphism (AFLP) analysis in order to assess the potential value of Swiss Mattenklee landraces as genetic resources for plant breeding and the preservation of biodiversity. Populations were classified into three groups according to their origin and agronomic features: Mattenklee landraces (8), Mattenklee cultivars (8) and field clover cultivars (3). Analysis of molecular variance based on 276 polymorphic AFLP markers revealed 80% of total variability to be due to variability within populations while 12% were attributed to variability among groups. Stepwise discriminant analysis identified a subset of 126 AFLP markers which best separated individual plants into the three respective groups. Genetic distances between populations were considerably larger among groups than among populations within the same group, providing further evidence for the genetic distinction between Mattenklee landraces, Mattenklee cultivars and field clover cultivars. AFLP markers identified two landrace clusters, containing three and four populations respectively, which, together with one additional landrace, may sufficiently represent the genetic variability of all eight landraces investigated. The results of this study strongly suggest that Swiss Mattenklee landraces form a genetically distinct group of red clover. The data obtained provide criteria on how to efficiently manage, preserve and exploit Mattenklee germplasm

QTL analysis of seed yield components in red clover (Trifolium pratense L.)

Cultivars of red clover (Trifolium pratense L.), an important forage crop in temperate regions, are often characterised by an unsatisfactory level of seed yield, leading to high production costs. This complex trait is influenced by many components and negatively correlated with other important traits, such as forage yield or persistence. Therefore, seed yield has proven to be difficult to improve. Thus, the objectives of this study were to assess association among seed yield components and to provide the basis for identifying molecular markers linked to QTLs for seed yield components to assist breeding for improved red clover cultivars. A total of 42 SSR and 216 AFLP loci were used to construct a molecular linkage map with a total map length of 444.2 cM and an average distance between loci of 1.7 cM. A total of 38 QTLs were identified for eight seed yield components. The traits seed number per plant, seed yield per head, seed number per head, head number per plant and percent seed set were highly correlated with seed yield per plant, and QTLs for several of these traits were often detected in the same genome region. Head number per plant may present a particularly useful character for the improvement of seed yield since it can easily be determined before seed maturity. In addition, two genome regions containing four or five QTLs for different seed yield components, respectively, were identified representing candidate regions for further characterisation of QTLs. This study revealed several key components which may facilitate further improvement of seed yield. The QTLs identified represent an important first step towards marker-assisted breeding in red clover

Sind Ökotypen von Welschem Weidelgras für den Ökolandbau besser geeignet als Zuchtsorten?

Ten ecotype populations of Italian ryegrass collected in permanent grassland in different regions of Switzerland were compared to two currently recommended cultivars in plot trials under both organic and conventional conditions. On average, the ecotypes had similar yields as the cultivars under organic conditions, but significantly outyielded them under conventional conditions. However, some of the best ecotype populations appeared to be also very suitable for organic agriculture. All ecotypes were extremely susceptible to crown rust. Therefore, targeted selection is needed to exploit their potential for use in organic agriculture

Genetic mapping reveals a single major QTL for bacterial wilt resistance in Italian ryegrass (Lolium multiflorum Lam.)

Bacterial wilt caused by Xanthomonas translucens pv. graminis (Xtg) is a major disease of economically important forage crops such as ryegrasses and fescues. Targeted breeding based on seedling inoculation has resulted in cultivars with considerable levels of resistance. However, the mechanisms of inheritance of resistance are poorly understood and further breeding progress is difficult to obtain. This study aimed to assess the relevance of the seedling screening in the glasshouse for adult plant resistance in the field and to investigate genetic control of resistance to bacterial wilt in Italian ryegrass (Lolium multiflorum Lam.). A mapping population consisting of 306 F1 individuals was established and resistance to bacterial wilt was assessed in glasshouse and field experiments. Highly correlated data (r = 0.67–0.77, P < 0.01) between trial locations demonstrated the suitability of glasshouse screens for phenotypic selection. Analysis of quantitative trait loci (QTL) based on a high density genetic linkage map consisting of 368 amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers revealed a single major QTL on linkage group (LG) 4 explaining 67% of the total phenotypic variance (Vp). In addition, a minor QTL was observed on LG 5. Field experiments confirmed the major QTL on LG 4 to explain 43% (in 2004) to 84% (in 2005) of Vp and also revealed additional minor QTLs on LG 1, LG 4 and LG 6. The identified QTLs and the closely linked markers represent important targets for marker-assisted selection of Italian ryegrass

An Increasing Need for Productive and Stress Resilient Festulolium Amphiploids:What Can Be Learnt from the Stable Genomic Composition of Festuca pratensis subsp. apennina (De Not.) Hegi?

Genome composition of Festuca pratensis subsp. apennina (De Not.) Hegi, a tetraploid fescue species native to the tall forbs communities of south-eastern Europe at altitudes between 1100 and 2200m a.s.l. has been the subject of some debate by grass taxonomists. Our cytogenetic analyses including fluorescence in situ hybridisation with probes for genomic DNA and selected DNA repeats revealed the species to be allotetraploid and derived from interspecific hybridization between F. pratensis Huds., a species confined to grassland at lower altitudes, and a so far unknown Festuca species. Besides tetraploids, triploids and pentaploids were found growing in Alpine meadows in close association with F. pratensis subsp. apennina. Triploid cytotypes predominated at many sites in Switzerland and Romania, and in some localities, they were the only cytotypes observed. Cytogenetic analyses revealed the triploids to be hybrids between diploid F. pratensis and tetraploid Festuca pratensis subsp. apennina, while the pentaploid cytotypes originated from hybridization between F. pratensis subsp. apennina and hexaploid F. arundinacea Schreb., a closely-related species growing in a close vicinity to F. pratensis subsp. apennina. Parental genomes of F. pratensis subsp. apennina and of the triploid and pentaploid hybrids showed no evidence of homoeologous chromosome pairing and interspecific recombination, supporting previous observation of a disomic inheritance at meiosis, where chromosome pairing was restricted to bivalent associations. A hypothesis is presented that a chromosome pairing regulator(s), reported previously in other polyploid broad-leaved fescue species of the Festuca subg. Schedonorus, is present and functional in F. pratensis subsp. apennina. It is likely that a common ancestors’ genome that carries the chromosome pairing regulator(s) is present in all polyploid broad-leaved fescue species, and its acquisition was a key event that enabled speciation, and development of a polyploid series within Festuca. Identification of a functional chromosome pairing regulator capable of stabilizing advantageous genome combinations in hybrids within the Lolium-Festuca complex would greatly assist in development of stable Festulolium cultivars. Its expression within Festulolium amphiploid cultivars would assist strategies aimed at climate-proofing productive European grasslands to combat exposures to stress conditions

A state of the art of germplasm collections for forage and turf species

v2010o

Plant Breeding: the Art of Bringing Science to Life. Abstracts of the 20th EUCARPIA General Congress, 29 Aug - 1 Sep 2016, ETH Zurich, Switzerland

Abstract book of 426 pages No proceedings of full articles will be publishe

Optimization of bulked AFLP analysis and its application for exploring diversity of natural and cultivated populations of red clover

Landraces and wild populations of red clover (Trifolium pratense L.) may represent a significant yet poorly characterized genetic resource of temperate grasslands. A bulking strategy with amplified fragment length polymorphism (AFLP) markers was optimized to characterize 120 red clover populations in 6 different groups: Swiss wild clover populations, Mattenklee landraces, Mattenklee cultivars, field clover cultivars, Dutch wild clover populations, and Dutch landraces. Analysis of 2 bulked samples/population consisting of 20 plants each with12 AFLP primer combinations was found optimal for determining genetic diversity and relationships within and among red clover populations and groups. Swiss wild clover populations were clearly separated from all other red clover groups and variability within and among populations was shown to be particularly high in wild clover populations and Mattenklee landraces, emphasising their value as genetic resources for improvement of red clover cultivars, as well as for conservation and restoration of biodiversity. This study shows that the ancestry of red clover landraces is primarily found in introduced cultivars rather than in natural wild clover populations. In addition, the methodological considerations presented here may help improve diversity analyses using bulked samples.Les variétés de pays et les populations sauvages du trèfle rouge (Trifolium pratenseL.) constituent possible-ment une ressource génétique considérable pour les prairies des zones tempérées, mais elles demeurent mal connues.Une stratégie d’analyse massale à l’aide de marqueurs AFLP (polymorphisme de longueur des produits amplifiés) a étéoptimisée afin de caractériser 120 populations de trèfle rouge appartenant à 6 groupes différents : trèfle sauvage suisse,variétés de pays de Mattenklee, cultivars de Mattenklee, cultivars de trèfle des champs, trèfle sauvage hollandais, varié-tés de pays hollandaises. L’analyse de 2 échantillons (amalgame de 20 plantes) par population à l’aide de 12 combinai-sons d’amorces AFLP s’est avérée optimale pour mesurer la diversité génétique et déterminer les relations parmi etentre les populations et groupes. Les populations du trèfle sauvage suisse étaient nettement séparées de tous les autresgroupes de trèfle rouge et la variabilité tant entre les populations qu’au sein de celles-ci était particulièrement élevéechez les populations de trèfle sauvage et chez les variétés de pays Mattenklee. Cela démontre leur intérêt en tant queressource génétique pour l’amélioration des cultivars de trèfle rouge de même que pour leur conservation et la restaura-tion de la biodiversité. Cette étude montre que les ancêtres des variétés de pays du trèfle rouge se trouvent principale-ment parmi les cultivars introduits plutôt qu’au sein des populations naturelles de trèfles sauvages. De plus, lesconsidérations méthodologiques présentées par les auteurs peuvent aider à améliorer les analyses de diversité faisantappel à des échantillons composés

Improving Persistence in Red Clover: Insights from QTL Analysis and Comparative Phenotypic Evaluation

Cultivars of red clover (Trifolium pratense L.) often suffer from low persistence, leading to insufficient legume proportions in pluriannual forage stands. Persistence is a complex trait often negatively correlated with other important traits and its phenotyping is laborious. Consequently, persistence is difficult to improve. The objectives of this study were to optimize the phenotypic evaluation of persistence, to identify quantitative trait loci (QTLs) for this important trait, and to investigate the association of persistence with other important traits. A weighted average of vigor scores assessed during two winters and three growing seasons was identified as the optimal method to phenotype persistence. For this index, one QTL explaining 12.2% of the total phenotypic variation was identified. While there was no negative correlation between persistence and seed yield, persistence was positively correlated with length of stem, which in turn was positively correlated with seed yield. Furthermore, QTLs for persistence, length of stem, and seed yield were detected in the same genome region. Improvement of persistence should therefore be possible without adverse effects on seed yield. Moreover, length of stem may present a candidate character for indirect selection of these two traits. The QTLs and the indirect selection criteria identified in this study may substantially assist future breeding efforts for the improvement of persistence in red clover