Time resolved fluorescence measurements on Tb3+ and Mn2+ doped glasses

Tb3+ (4f8) and Mn2+ (3d5) ions, known as active luminescent centres for blue, green and red fluorescence, were doped in various fluoride, phosphate and Silicate glasses with well known structure. Narrow bands of f-f transitions with strong emission of Tb3+ in the blue, green and red and broad bands of d-d transitions of Mn2+ were measured with green emission in high optical basicity glasses with tetrahedrally coordinated Mn2+. Orange to red Mn2+ emission was found in glasses with low optical basicity where Mn2+ is octahedrally coordinated. Lifetimes, τe, in the range of milliseconds were recorded in dependence of glass composition and dopant concentration for both Tb3+ and Mn2+ doped glasses. Fluorescence lifetimes are as well shortened by higher basicity of the glasses as by increasing dopant concentration

Sample size for diversity studies in tetraploid alfalfa (Medicago sativa) based on codominantly coded SSR markers

The number of genotypes investigated per population is important for the reliability of diversity studies. The objective of this study was to determine the sample size for the identification of differences among populations of an outcrossing autotetraploid species, alfalfa (Medicago sativa), using codominantly coded SSR markers. One hundred and twenty genotypes from each of two closely related populations were analysed with two markers. Twenty random subsamples for each of three sample sizes (10, 20 and 40 genotypes) were built. Compared to the populations with 120 genotypes, alleles that were no longer present in subsamples with 40 genotypes were mainly rare, whereas abundant alleles were also excluded in subsamples with 10 genotypes. F ST values for pairs of subsamples between the two populations were always significantly different based on 40 genotypes, whereas for 10 genotypes more than half of the pairs were not significantly different. We concluded that 40 genotypes are a reasonable sample size for diversity studies with closely related populations of tetraploid alfalfa investigated with SSR markers. Twenty genotypes may be an economical alternative for large scale studies, but 10 genotypes were a too low number for reliable results

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

Association of a CONSTANS-LIKE gene to flowering and height in autotetraploid alfalfa

In alfalfa (Medicago sativa), an autotetraploid forage legume, stem length is a major component of forage yield, quality and competing ability. In this species, flowering date is not a breeding criterion. Association mapping based on a candidate gene approach has given good results in plants, including autotetraploid species for which genetic analyses are complex. The role of a CONSTANS-LIKE gene, identified as a candidate for stem elongation and flowering date in the model legume M. truncatula, was tested for association with the same traits in alfalfa. Four hundred genotypes from ten cultivars were evaluated for stem height and flowering date in two locations during 4 years. They were genotyped with simple sequence repeat markers and a low structuration was noticed. Primers were designed to amplify and sequence two regions of the alfalfa gene homologous to CONSTANS-LIKE. Single nucleotide polymorphisms (SNPs) were detected and their allelic dose in each genotype was scored. Linkage disequilibrium within CONSTANS-LIKE rapidly decreased as expected. Eight SNPs with a frequency above 10% were detected over 1,010 bp (one SNP every 126 bp on average) in the 400 genotypes. This number was lower than observed in a neutral gene (a SNP every 31 bp on average). Highly significant associations of three SNPs to flowering date and stem height were identified. Each SNP explained up to 4.2% of the genetic variance. Thus, as in the model species, the CONSTANS-LIKE gene was shown to be involved in flowering date and stem height in alfalfa

Unterscheidung von Getreidesorten durch Elektrophorese

Die Identifikation von Getreidesorten ist am Ernte gut von blossem Auge nicht möglich. Die elektrophoretische Auftrennung von Speicherproteinen wie zum Beispiel Gliadinen ist eine mögliche Methode zur Sortenidentifikation am Erntegut. Dank der hohen Variabilität der Gliadine entsteht ein sortenspezifisches Bandenmuster. Wir haben die Getreidesorten der schweizerischen Sortenliste und fortgeschrittene Zuchtlinien des Schweizer Zuchtprogramms auf ihre Unterschiede im Gliadin-Bandenmusteruntersucht. Dazu verwendeten wir die Acid Polyacrylamid Gel Electrophoresis (A-PAGE). Bei Weizen fanden wir bei den 28 untersuchten Sorten 26 verschiedene Bandenmuster. Somit sind die Weizensorten mit A-PAGE gut unterscheidbar. Dies gilt auch für die Gersten- und Hafersorten. Dagegen zeigten fast alle Dinkelsorten das gleiche Gliadin-Bandenmuster. Roggensorten bilden als Fremdbefruchter kein homogenes Muster. Die Getreidearten zeigen alle ein artspezifisches Bandenmuster. Die diploiden Arten Gerste, Hafer und Roggen haben ein einfacheres Muster als die hexaploiden Weizen, Triticaleund Dinkel. Die A-PAGE-Methode ist zeitaufwändig und arbeitsintensiv. Aus diesem Grunde testeten wir auch die isoelektrische Fokussierung (IEF). Mittels IEF wurden die Glutenine, eine weitere Speicherproteinfraktion, aufgetrennt. Die 28 Weizensorten zeigten nur elfunterschiedliche Glutenin-Bandenmuster. IEF bildet jedoch eine effiziente Alternativebei der Unterscheidung vor allem zwischen den freidreschenden Getreidearten

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

A CONSTANS-like gene candidate that could explain most of the genetic variation for flowering date in Medicago truncatula

Flowering is a critical period during a plant’s life cycle, and thus the identification and characterization of genes involved in flowering date control are of great importance in agronomy, breeding, population genetics and ecology. The model species Medicago truncatula can be used to detect genes explaining the variation for flowering date, which could also explain this variation in legume crops. The objective of this study was to identify the most promising candidate gene explaining a major quantitative trait locus (QTL) for flowering date previously found in three M. truncatula mapping populations. Fine mapping and bioinformatic analysis of bacterial artificial chromosomes (BACs) in the confidence interval of the QTL showed six genes potentially involved in the control of flowering date. Two of these genes, similar to CONSTANS and FT of Arabidopsis thaliana respectively, had genomic mutations when compared to the parents. The transcriptomic study of these genes by semi-quantitative RT-PCR in leaves and flowers sampled at two developmental stages showed that the CONSTANS-like gene was differentially expressed in the two parental lines. A gene belonging to the CONSTANS-like family could explain the major QTL for flowering date segregating in M. truncatula progenies

Im Dienst für die Forschung = Au service de la recherche

10 Jahre lang leitete Doris Herrmann das Ressort Forschung, Dienstleistungen und Weiterbildung an der BFH-HAFL. Ihre nächste Station: Leiterin des Fachbereichs Forschung, Beratung und Innovation am Bundesamt für Landwirtschaft BLW.Doris Herrmann a été pendant 10 ans responsable du bureau Recherche, prestations, formation continue à la BFH-HAFL. Sa prochaine étape : la direction du secteur Recherche, vulgarisation et innovation de l’Office fédéral de l’agriculture

Structuration de la diversité génétique chez la luzerne cultivée, conséquence pour l'identification de gènes liés à des caractères agronomiques

La luzerne, espèce allogame et autotétraploïde, est une légumineuse fourragère dont l’intérêt connaît un renouveau certain grâce à ses atouts pour le développement durable de l’agriculture. L’amélioration des variétés nécessite de mieux connaître les ressources génétiques, pour les exploiter, que ce soit en sélection classique ou en utilisant les outils moléculaires pour implémenter la sélection assistée par marqueurs. En étudiant 10 variétés européennes, nous avons montré que la diversité à l’intérieur des variétés est grande (hétérozygotie attendue de 0.75, déviation standard de 0.80, pour des caractères phénotypiques et des marqueurs moléculaires neutres, respectivement). La différenciation entre variétés est notable pour les caractères phénotypiques. Cette structuration de la diversité est favorable à l’utilisation de la génétique d’association basée sur des gènes candidats pour identifier des gènes liés à des caractères agronomiques. Une telle étude a permis de montrer que le gène Constans-like contribue à expliquer les différences de longueur de tiges chez la luzerne, une composante du rendement fourrager. Alfalfa, an allogamous and autotetraploid species, is a forage legume for which a renewed interest has raised because of its advantages for a sustainable agriculture. Variety improvement requires a better knowledge of the genetic resources in order to exploit them, with classical breeding methods or with molecular tools to implement marker assisted selection. We have described 10 European varieties and found a large within-variety diversity (expected heterozygozity of 0.75, standard deviation of 0.80, with phenotypic traits and neutral molecular markers, respectively). Differentiation between varieties was noticeable for phenotypic traits. This genetic structure of diversity is favourable to the use of association genetics based on candidate genes to identify genes related to agronomic traits. Such a study showed that Constans-like gene contributes to explain differences in alfalfa stem length, a component of forage yield

The research of the pulsed electron beam effect on polylactic acid scaffolds

The effect of nanosecond pulsed electron beam irradiation on properties of polylactic acid (PLLA)scaffolds was investigated. Modification of scaffolds was performed in electron beam accelerator with absorbeddose from 30 to200 kGy. Properties of the scaffolds were examined by means of XRD analysis and scanningelectron microscopy. It was shown that pulsed electron beam exposure leads to the recrystallization and changesin surface morphology