Papers by Stephen Langrell
Isolation and characterisation of simple sequence repeat loci in Armillaria ostoyae
HAL (Le Centre pour la Communication Scientifique Directe), Mar 25, 2001
Molecular phylogeny, detection and epidemiology of Nectria canker (Nectria Galligena Bres.)
ABSTRACT Thesis (Ph. D.)--University of London, Jan 2000.
Fungal Biology, Jul 1, 2011
Soil borne Phytophthora cinnamomi and Phytophthora cambivora are considered the most pathogenic s... more Soil borne Phytophthora cinnamomi and Phytophthora cambivora are considered the most pathogenic species associated with chestnut (Castanea sativa) decline in Europe. Mapping their incidence and distribution from nursery and plantation soils may offer valuable information for limiting spread. As conventional biological baiting and taxonomic confirmation is generally time consuming, labour, logistically and space intensive, we have focused on the development of a specific touchdown nested multiplex Polymerase Chain Reaction (PCR) approach for the simultaneous detection of both species direct from soil. Pre-existing and novel primers, based on Internal Transcribed Spacer (ITS) sequences, have been evaluated for their specificity and use in a multiplex capacity in various combinations. Coupled to this we have modified a mechanical lysis procedure for DNA extraction from up to 10 g of chestnut under storey soils (ranging from 0.5 to 25 mg DNA g À1 fresh soil). Using serial dilutions and/or polyvinylpolypyrrolidone chromatography purification, both species have been successfully detected, in artificially and naturally infected soils. Levels of assay detection are comparable to other Phytophthora species where PCR based diagnostic systems have been reported. A qualitative evaluation of this approach against conventional baiting is presented.
Fems Microbiology Letters, 2005
A pair of primers specific for Nectria fuckeliana, a bark infecting pathogen predominantly of Nor... more A pair of primers specific for Nectria fuckeliana, a bark infecting pathogen predominantly of Norway spruce (Picea abies), were designed from comparisons of nucleotide sequences of the nuclear ribosomal internal transcribed spacer (ITS) regions of nine isolates from Norway,
Molecular Ecology Resources, Mar 2, 2011
Red band needle blight is one of the most important foliar diseases of Pinus species and is of in... more Red band needle blight is one of the most important foliar diseases of Pinus species and is of increasing international forest health and biosecurity concern. To provide a rapid identification technique for this pathogen in support of official control measures, a nested polymerase chain reaction-based diagnostic assay that employs species-specific primer sets has been developed. The assay is able to detect the presence of the pathogen direct from pine needles, irrespective of host species, to within 10 fg of target DNA, the equivalent of approximately 2-3 ascospores or hyphael cells.
Phytopathology, Feb 1, 2007
Development of nested polymerase chain reaction detection of Mycosphaerella spp. and its applicat... more Development of nested polymerase chain reaction detection of Mycosphaerella spp. and its application to the study of leaf disease in Eucalyptus plantations. Phytopathology 97:132-144. Mycosphaerella leaf disease (MLD) is a serious disease of two of the major eucalypt species grown in temperate regions worldwide, Eucalyptus globulus and E. nitens. More than 30 species of Mycosphaerella have been reported on eucalypts worldwide. Accurate, rapid, and early discrimination of Mycosphaerella spp. causing crown damage to E. globulus and E. nitens will assist the development of sustainable management strategies. This study describes the development, and incorporation in a nested polymerase chain reaction (PCR) approach, of specific primers for the detection and identification of Mycosphaerella spp. commonly reported from leaf lesions of E. globulus and E. nitens in Australia. Primer design was assisted by sequence alignment and phylogenetic analysis of 165 nonredundant sequences from the nuclear ribosomal DNA internal transcribed spacer regions of Mycosphaerella and related species. Phylogenetic analysis revealed very high sequence similarity for two taxon groups, Mycosphaerella grandis and M. parva, and M. vespa, M. ambi-phylla, and M. molleriana, and primers were designed to differentiate each of the two groups. Three other species, M. cryptica, M. nubilosa, and M. tasmaniensis, were distinct and distinguished by species-specific primers. In double-blind trials, the detection test accurately and rapidly identified Mycosphaerella spp. in cultures and discriminated against other pathogens that co-occur in or on Eucalyptus leaves, thereby verifying its reliability. The detection test has an internal amplification control in the first-round PCR with fungal-specific primers to raise confidence in test results, particularly to highlight negative results due to PCR inhibition. When applied to DNA extracted from leaf or stem samples either as multiple or single lesions, it detected and identified up to five Mycosphaerella spp. or taxon groups in both positively identified and in young (putative) MLD lesions. The samples were 20 mm 2 or larger in surface area and were collected while undertaking disease rating assessments in an experimental investigation of Eucalyptus plantations and regrowth forest. Using nested PCR detection, Mycosphaerella spp. were positively identified in 2 days, 1 to 5 months earlier than by classical methods, demonstrating the potential application of this detection test to the early discrimination of MLD components in ecological, epidemiological, and genetic investigations. Eucalyptus spp. are a major global hardwood pulp crop. Mycosphaerella spp. cause severe leaf diseases of temperate Eucalyptus plantations in wetter areas of Australia and serious disease in New Zealand, South Africa, Spain, and some regions of Chile (19). Many species appear to have spread to other temperate regions from Australia, and species that also occur in the Australian subtropics appear to have spread to Indonesia, Vietnam, China, and South America (21,58,62). Indigenous temperate Australian forests have mixed eucalypt species where Mycosphaerella leaf disease (MLD) generally is of minor significance, except in coppice regrowth in certain Western Australian forests (1,14). In southern Australia, MLD in plantations appears to be caused principally by Mycosphaerella nubilosa and M. cryptica, although M. vespa, M. tasmaniensis, M. parva, and M. grandis occur frequently. M. marksii and other species are encountered less often (13,49,51,52,60). The most damaging are reported to be M. nubilosa and M. cryptica (10-12,14,25,59-62), which cause the most severe leaf disease, resulting in significant crown damage of E. globulus, E. nitens, and their hybrids (30,39), the most widely
HAL (Le Centre pour la Communication Scientifique Directe), Sep 17, 2001
Phyla scaberrima (Verbenaceae) is a herbaceous species distributed from Mexico to Panama. Because... more Phyla scaberrima (Verbenaceae) is a herbaceous species distributed from Mexico to Panama. Because of its well-known sweet properties and other medicinal uses, this species is cultivated in South America and the Caribbean. Phyla scaberrima has been arbitrarily extracted from nature, resulting in a severe reduction in its gene pool. In this study, we developed and characterized 11 simple sequence repeat markers for P. scaberrima to determine the genetic variability and patterns of population structure of the species. Fifty-six alleles were detected in a sample of 48 individuals belonging to 3 different populations. The average number of alleles per locus was 5.09, while the polymorphic information content ranged from 0.000-0.587. The observed and expected heterozygosities varied from 0.000-0.543 and from 0.000-0.651, respectively. Two loci exhibited significant deviation of the expected Hardy-Weinberg proportion. The 11 primer pairs were ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (3): 7864-7868 (2014) Isolation of SSR loci for Phyla scaberrima also tested for cross-amplification to 6 species of the related genus Lippia. The transferability rate ranged from 4 loci in Lippia florida and L. rotundifolia to 6 loci in L. corymbosa and L. microcephala. The 11 primer sets were shown to be valuable tools for population genetic studies in P. scaberrima and in species of the genus Lippia in which primer transferability was detected.
Isolation and characterization of polymorphic simple sequence repeat loci in Armillaria ostoyae
HAL (Le Centre pour la Communication Scientifique Directe), 2001
Molecular Ecology Notes, Jun 1, 2002
Cross-species PCR amplification of Armillaria mellea group taxa with previously reported A. ostoy... more Cross-species PCR amplification of Armillaria mellea group taxa with previously reported A. ostoyae microsatellite markers, indicative of flanking sequence conservation, was exploited for the species-specific isolation of simple sequence repeat (SSR) motifs from A. gallica. Six SSR motifs were sequence characterized from cloned PCR fragments generated with primers previously developed from A. ostoyae. Five novel primer pairs, designed from motif flanking regions, allowed for improved, efficient amplification in this species. One original A. ostoyae primer pair was used directly. Polymorphims were observed at wide geographical levels only. Relative cross-species amplification intensities generally supported the currently accepted molecular phylogeny of this group.
First Report of <i>Colletotrichum acutatum</i> on <i>Kalmia</i>
Plant Disease, Apr 1, 2001
Colletotrichum acutatum J. H. Simmonds was isolated from diseased leaves of ornamental Kalmia lat... more Colletotrichum acutatum J. H. Simmonds was isolated from diseased leaves of ornamental Kalmia latifolia L. (mountain laurel) cvs. Carousel and Peppermint on plants imported from the United States to Edinburgh, Scotland, in December 1999. Symptoms included sunken, desiccated, darkened necrotic areas, primarily at the leaf tip. Necrotic areas advanced toward the leaf base and were bordered by purple/red pigmentation. Isolations were made from salmon colored conidiomata that developed on abaxial leaf surfaces following incubation in a humidity box at 25°C for 7 to 10 days. White aerial mycelia, becoming gray to grayish beige, and producing salmon to orange colored conidial masses, formed on potato dextrose agar after 10 to 14 days. Conidia were hyaline, aseptate, fusiform to slightly irregular, and measured 13.4 to 13.8 × 4.3 to 4.9 μm. Both morphological and conidial characteristics were consistent with the description of C. acutatum (2). The identity of isolates was further verified by positive plate-trapped antigen ELISA of conidial preparations using a species-specific monoclonal antibody (1). Pathogenicity was assessed by inoculating the adaxial surface of healthy leaves of both cultivars of the imported plants with colonized agar disks and a range of spore suspensions (30, 300, and 3,000 spores delivered in 30 μl volumes) from test fungal isolates and a confirmed laboratory strain (three replicates per treatment). To ensure inoculum uptake, two 5 mm2 areas of cuticle on either side of the mid-rib of each leaf were lightly scratched with a sterile hyperdermic needle prior to inoculation. Inoculated leaves were incubated in a humidity box at 25°C for up to 3 weeks. Symptom development was progressive but relatively slow on both cultivars. The relatively slow development on artificially infected leaf material may be partly attributable to residual fungicide treatment as prescribed by the Scottish Plant Health Service at the time of planting out. Symptoms produced on fruits (apple, banana, and strawberry), inoculated with both test and laboratory strains of the fungus, were identical. Symptoms did not occur on control leaves or fruits inoculated with sterile distilled water or uninoculated agar disks. Koch's postulates were confirmed by consistently reisolating isolates with morphological and immunological characteristics identical to the fungal isolate used to initially inoculate test material. Over the same period, additional symptoms, identical to those originally described at the time of interception, continued to develop on leaf tips of both Kalmia cultivars. Additional isolations from this material were characterized as C. acutatum. Identification of representative isolates was confirmed by CABI Bioscience, Egham, UK, where a reference culture (accession number IMI 384569) has been deposited. As advanced symptoms were observed immediately on arrival of this consignment in the UK, original infection is thought to have occurred prior to importation. This is the first report of C. acutatum infecting K. latifolia. References: (1) I. Barker et al. 1994. Pages 179-182 in: Assays for Plant Pathogenic Fungi: Identification, Detection and Quantification. A. Schots, F. M. Dewey, and R. Oliver, eds. CABI International, Wallingford, UK. (2) B. J. Dyko and J. E. M. Mordue. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 630, 1979.
Isolation and characterization of polymorphic simple sequence repeat loci in <i>Armillaria ostoyae</i>
Molecular Ecology Notes, Dec 1, 2001
ABSTRACT A modified hybridization strategy was used to construct a microsatellite enriched librar... more ABSTRACT A modified hybridization strategy was used to construct a microsatellite enriched library from DNA of Armillaria ostoyae, a serious root pathogen on pine. Sequence characterization of 19 random clones revealed 12 distinct loci harbouring a repetitive motif. Primer design from the flanking regions allowed for their development as polymerase chain reaction based markers. Polymorphic assessment at both the population and global levels revealed levels of variation useful for genetic studies. The level of cross-species amplification observed with closely related Armillaria species was high, raising the possible exploitation of these primers across the genus.
Relative significance of nursery infections and orchard inoculum in the development and spread of apple canker (Nectria galligena) in young orchards
Plant Pathology, 2003
Three nurseries produced apple rootstocks (M9) and budwood (cv. Royal Gala), which they exchanged... more Three nurseries produced apple rootstocks (M9) and budwood (cv. Royal Gala), which they exchanged at the end of the first year. Each nursery then budded its own budwood onto the rootstocks it had produced and that from the other two nurseries. Budded trees were grown on for a further year before being planted at HRI, East Malling in southern England; NIHPBS, Loughgall in Northern Ireland; and ADAS, Rosemaund in the West Midlands of England. Canker development was monitored twice a year. The position of the infected trees within the orchard was recorded, as was the position of the canker on each tree (main‐stem or peripheral). Nectria galligena was isolated from representative cankers and analysed using molecular techniques. At the sites in Northern Ireland and HRI there was a strong positional effect, especially of peripheral cankers, indicating that most of the inoculum was external and had been spread from neighbouring orchards. There was little or no positional effect on main‐ste...
Review of Agricultural, Food and Environmental Studies, 2017
A realistic experiment with 189 French consumers was conducted to analyse consumers' reaction to ... more A realistic experiment with 189 French consumers was conducted to analyse consumers' reaction to the transition towards Integrated Pest Management (IPM) as the standard in European farming. Results indicate high substitutability between IPM and organic tomatoes. It suggests IPM sales will benefit from the withdrawal of conventional products from the market only if there is a significant reduction in the price of IPM products as compared to organic ones and/or an important increase in the shelf space dedicated to IPM products. While information on IPM guidelines increases IPM products purchases, providing extra information on residue levels in IPM tomatoes has no further impact on consumers' choices in this experiment.
Data from: Nested polymerase chain reaction–based detection of Dothistroma septosporum, red band needle blight of pine, a tool in support of phytosanitary regimes
Red band needle blight is one of the most important foliar diseases of Pinus species and is of in... more Red band needle blight is one of the most important foliar diseases of Pinus species and is of increasing international forest health and biosecurity concern. To provide a rapid identification technique for this pathogen in support of official control measures, a nested polymerase chain reaction–based diagnostic assay that employs species-specific primer sets has been developed. The assay is able to detect the presence of the pathogen direct from pine needles, irrespective of host species, to within 10 fg of target DNA, the equivalent of approximately 2–3 ascospores or hyphael cells
introduction of GM crops into european agriculture: a summary report of the FP6 SIGMEA research p... more introduction of GM crops into european agriculture: a summary report of the FP6 SIGMEA research project*
This report synthesises the findings from the workshop on “Sustainability and Production Costs in... more This report synthesises the findings from the workshop on “Sustainability and Production Costs in the Global Farming Sector: Comparative Analysis and Methodologies” organised jointly by the IPTS-JRC and the Directorate-General for Agriculture and Rural Development in Brussels on 21-22 June 2011. The report constitutes a comprehensive technical overview of the state of production costs calculations for a range of strategic agricultural sectors at global level, and a consideration of the prospects for effective international comparison. Particular attention was given to the methodologies and approaches for data collection and processing, factor market structure and policy inter-linkages, sectoral coverage, horizontal technical issues, and the implications for global agricultural markets. An important part of the report represents policy-relevant conclusions and recommendations for conducting an effective international comparative analysis of production costs.
We would like to thank all participants who readily gave of their experiences and expertise of re... more We would like to thank all participants who readily gave of their experiences and expertise of regional and global food security, challenges of wheat production from across the Eurasian wheat belt region, as well as with complex issues associated with national, regional and global economic and market drivers, presented and discussed at the workshop on "The role of the Eurasian wheat belt to regional and global food security"
American Journal of Veterinary Research, 2012
Climate change is increasingly perceived as one of the major constraints that limit agricultural ... more Climate change is increasingly perceived as one of the major constraints that limit agricultural productivity. Crop losses due to climate change could be direct, such as damages through flooding or storms, or indirect such as altered distribution of crop pests. The real impact of climate change at global level is yet uncertain and likely variable from one region to another. Within this context, it is difficult to predict effects of climate change, particularly when long-term datasets from the past are missing to develop and test predictive models for the future. Nevertheless, our knowledge of plant-disease interactions, population genetics of pathogens as well as crops, and examples of overwhelming establishment of new diseases in a given region provides insights into how climate change may affect disease incidence and severity. Here we report examples of pest populations which have been established across regions previously considered detrimental for their survival and yield losses...
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Papers by Stephen Langrell