New Perspectives for the Use of Elms as Street Trees

As a result of the continuing problems with Dutch elm disease in the Netherlands the dominant role of elm as a street tree has diminished strongly in the last decades of the 20th century. New cultivars with increased resistance to DED are used to a limited extent only. This paper reports on the first results of a project that aims to restore the position of the elm as a street tree in the Netherlands by providing information on these new cultivars. In particular the relative levels of resistance and their value as street tree are being tested. From the preliminary results it follows that there is a large variation in resistance and that there are several cultivars available that show no or only limited symptoms after severe inoculation in an experimental field test. In addition design and first results of the evaluation of their value as street tree are described

DNA en herkolonisatie van boomsoorten na de laatste ijstijd, een els voor de toekomst.

Voor beheerders van openbaar groen is de wetenschappelijke onderbouwing van de tegenstelling tussen inheemse boom- en plantensoorten en exoten van een ondergeschikt belang. Boombeheerders kiezen doorgaans voor een pragmatische aanpak. Met het oog op het congres ‘Stilte voor de storm’ dat NDV organiseert leek het ons als vakblad zinnig een aantal sprekers door te zagen over hun inbreng. Op deze pagina’s een samenvatting van de lezing van Joukje Buiteveld. Zij is als populatiegeneticus werkzaam bij Alterr

Population estimators or progeny tests: what is the best method to assess null allele frequencies at SSR loci?

Nuclear SSRs are notorious for having relatively high frequencies of null alleles, i.e. alleles that fail to amplify and are thus recessive and undetected in heterozygotes. In this paper, we compare two kinds of approaches for estimating null allele frequencies at seven nuclear microsatellite markers in three French Fagus sylvatica populations: (1) maximum likelihood methods that compare observed and expected homozygote frequencies in the population under the assumption of Hardy-Weinberg equilibrium and (2) direct null allele frequency estimates from progeny where parent genotypes are known. We show that null allele frequencies are high in F. sylvatica (7.0% on average with the population method, 5.1% with the progeny method), and that estimates are consistent between the two approaches, especially when the number of sampled maternal half-sib progeny arrays is large. With null allele frequencies ranging between 5% and 8% on average across loci, population genetic parameters such as genetic differentiation (F ST) may be mostly unbiased. However, using markers with such average prevalence of null alleles (up to 15% for some loci) can be seriously misleading in fine scale population studies and parentage analysi

Nieuwe autochtone herkomsten van fladderiep en boskers op de Rassenlijst Bomen

De aanbevelende Rassenlijst Bomen bevat twee nieuwe herkomsten van fladderiep (Ulmus laevis) en een nieuwe herkomst van boskers (Prunus avium). De Raad voor plantenrassen en het Bosschap maakten dit bekend. Het gaat in alle drie de gevallen om genenbankmateriaal dat is opgenomen in de categorie 'naar herkomst geïdentificeerd'

Regeneration and interspecific somatic hybridization in Allium for transfer of cytoplasmic male sterility to leek

The vast majority of the present day leek cultivars is of poor quality. The genetic constitution of leek makes it a difficult crop to breed and consequently mass, or family selection methods, both of which have a low efficiency, are mainly used. F 1 hybrid breeding seems the appropriate strategy for improvement of leek. With such a breeding system a higher uniformity of the crop, better fixation of desirable traits, such as pest and disease resistance and a better exploitation of heterosis effects can be achieved. Large-scale seed production of hybrid cultivars requires a hybridization system based on cytoplasmic male sterility (CMS), because of the considerable advantage of this system in maintaining the male sterile parent line. Since no source of CMS has yet been found in leek or related forms of A. ampeloprasum , several researchers are focused on introducing cytoplasmic male sterility into leek. In the present thesis the possibility of introducing CMS into leek via somatic hybridization with A. cepa as CMS donor was investigated. Successful application of such a technique requires an efficient system for regeneration of plants from protoplasts. At the beginning of the research project in 1990 such a protoplast-to-plant system for leek was not available. Therefore, substantial effort was directed towards the development of efficient plant regeneration methods from embryogenic callus cultures, suspension cultures and protoplasts.Initially, much attention was focused on development of regenerative callus cultures from different explants and cultivars. The highest compact callus response was obtained when mature, zygotic embryos were cultured on MS medium, containing 30 g/l sucrose and 1 mg/l 2,4-D. Significant differences were found between the cultivars and accessions for shoot formation frequency. In addition, a genotype-dependent response of leek embryo explants for the formation of shoots was evident.In contrast to plant regeneration from compact embryogenic callus of leek, which is efficient and easy to achieve, the establishment of suspension cultures from this type of callus was less successful. Although compact callus cultures in liquid medium retain their ability to form somatic embryos and shoots for a long period, they do not become a finely-dispersed suspension culture. For this purpose, a new friable embryogenic type of callus was induced on immature embryos instead of mature embryos. This friable callus comprised numerous globular embryoids, embedded in mucilage and is highly regenerative when plated on a cytokinin containing medium. It was found that the developmental stage of the immature embryo and the genotype of the donor plant significantly influenced the callus response. Characterization of the two callus types by a histological examination revealed striking differences and supported the suggestion that friable callus is more suitable for initiating suspension cultures than compact callus. A stringent selection within these friable callus cultures was necessary to obtain highly-embryogenic suspension cultures.A procedure was described for the isolation, culture and regeneration of plants from protoplasts derived from these embryogenic suspension cells. Imbedding in alginate was an important factor in increasing the plating efficiency. The regeneration frequency of the protoplast-derived calli was primarily affected by the type of callus that developed. The protoplast-to-plant system described was reproducible for at least three genotypes. Plants were regenerated within 6 months after protoplast isolation.Utilising this regeneration procedure for protoplasts, a method for symmetric hybridization between leek and onion as a CMS donor was set up. The fusion experiments yielded large numbers of hybrid calli and plants. The aneuploid status of the hybrid plants could be explained by the use of leek protoplasts, derived from an aneuploid suspension culture. This also implied that using cell suspensions as a protoplast source for fusion remains a restrictive factor in the establishment of a successful hybridization system for leek. The leaf morphology of the hybrids was intermediate between the two parents. It appeared that most of the hybrids possessed leek chloroplasts and a rearranged mitochondrial genome of both parents, but with a predominance of mtDNA fragments from leek.With the methods described in this thesis the first steps to transfer CMS to leek have been realized. The results described here show that a cytoplasm of onion can be successfully transferred to leek via somatic hybridization. Future research should focus on further improvement of the system. For this, optimization of some aspects of the regeneration process and developing an efficient selection system for the desired hybrids, containing the onion specific CMS mtDNA sequences should be accomplished. The research has shown that somatic hybridization has a high potential to obtain CMS leek plants.</p

Modelling global livestock diversity : a fuzzy cognitive mapping approach

For modelling global trends in agrobiodiversity better insight in the relationship between drivers (and related pressures) and agrobiodiversity is needed. In a previous study of the authors a number of indicators for genetic diversity were proposed as being suitable for modelling. In this working document it was investigated if a global agrobiodiversity map for livestock could be produced based on one of these earlier suggested indicators. The Global Domestic Animal Diversity Information System (DAD-IS) was interrogated for one livestock species (cattle) to investigate whether sufficient data of good quality is available to produce such a global map. Additionally, a fuzzy cognitive mapping approach was used to make a qualitative description of livestock diversity in relation to drivers of change. In the FCM 21 factors were identified by the workshop participants to describe the livestock diversity system, of which 10 appeared to be most influential. For these most important factors a list of relevant (proxy) indicators with their potential for use was suggested. These suggested indicators could be the basis for further research in which the so-called archetype methodology could be used to get insight in hotspots of livestock diversity

Identification of inclusions in lung tissue with a Raman microprobe

Inhaled particles smaller than 4 μm can cause damage to lung tissue, a disease called silicosis. We present an investigation on the use of a Raman microspectrometer for the identification of inclusions in lung tissue. We measured Raman spectra of such inclusions in lung tissue of a patient whose probable cause of death was silicosis. Most of the inclusions we could identify were calcite particles

Het belang van genetische diversiteit voor beleid en beheer

Genetisch onderzoek aan de voorbeeldsoorten zwarte populier, eik en beuk heeft veel nieuwe inzichten opgeleverd. Deze kennis kan gebruikt worden in het behee

Round-robin tournaments with homogeneous rounds

We study single and double round-robin tournaments for n teams, where in each round a fixed number (g) of teams is present and each team present plays a fixed number (m) of matches in this round. In a single, respectively double, round-robin tournament each pair of teams play one, respectively two, matches. In the latter case the two matches should be played in different rounds. We give necessary combinatorial conditions on the triples (n,g,m) for which such round-robin tournaments can exist, and discuss three general construction methods that concern the cases m=1, m=2 and m=g−1. For n≤20 these cases cover 149 of all 173 non-trivial cases that satisfy the necessary conditions. In 147 of these 149 cases a tournament can be constructed. For the remaining 24 cases the tournament does not exist in 2 cases, and is constructed in all other cases. Finally we consider the spreading of rounds for teams, and give some examples where well-spreading is either possible or impossible

First National Report on Forest Genetic Resources for Food and Agriculture,The Netherlands : country report for the FAO first state of the world's forest genetic resources for food and agriculture, Ministry of Economic Affairs, The Hague, November 2012

The Dutch national report is designed to contribute to a regional and global sysnthesis of the state of forest genetic resources and in particular to examine trends over the past ten years. After a general introduction to the Dutch forest sector and the historical background of today's forests, it describes the current state of forest genetic diversity in the Netherlands and the main factors influencing i