Showing papers by "CABI published in 2003"

Environmental risk assessment of exotic natural enemies used in inundative biological control

Abstract: In the past 100 years many exotic naturalenemies have been imported, mass reared andreleased as biological control agents. Negativeenvironmental effects of these releases haverarely been reported. The current popularity ofinundative biological control may, however,result in problems, as an increasing number ofactivities will be executed by persons nottrained in identification, evaluation andrelease of biological control agents.Therefore, a methodology for risk assessmenthas been developed within the EU-financedproject `Evaluating Environmental Risks ofBiological Control Introductions into Europe[ERBIC]' as a basis for regulation of importand release of exotic natural enemies used ininundative forms of biological control (i.e.not in `classical biological control' thoughsome of the same principles and approachesapply). This paper proposes a general frameworkof a risk assessment methodology for biologicalcontrol agents, integrating information on thepotential of an agent to establish, itsabilities to disperse, its host range, and itsdirect and indirect effects on non-targets. Ofthese parameters, estimating indirect effectson non-targets will be most difficult, asmyriads of indirect effects may occur whengeneralist natural enemies are introduced. Theparameter `host range' forms a central elementin the whole risk evaluation process, becauselack of host specificity might lead tounacceptable risk if the agent establishes anddisperses widely, whereas, in contrast, amonophagous biological control agent is notexpected to create serious risk even when itestablishes and disperses well. Drawing onpublished information and expert opinion, theproposed risk assessment methodology is appliedto a number of biological control agentscurrently in use. These illustrative casehistories indicate that the risk assessmentmethodology can discriminate between agents,with some species attaining low `risk indices'and others scoring moderate or high. Riskindices should, however, not be seen asabsolute values, but as indicators to which ajudgement can be connected by biologicalcontrol experts for granting permission torelease or not.

Animal Domestication and Behavior

Abstract: This text synthesizes existing knowledge of the process of domestication and how domestication has affected the behaviour of captive wild and domesticated animals, including both farm, zoo and companion animals. Three broad themes are addressed: genetic contributions to the process of domestication; experimental contributions to the process of domestication; the process of feraliztion (i.e. the adaptation of domesticated animals when returned to their natural habitat.

Endophytes and mycoparasites associated with an indigenous forest tree, Theobroma gileri , in Ecuador and a preliminary assessment of their potential as biocontrol agents of cocoa diseases

Abstract: The main constraint and continuing threat to cocoa production in Latin America is disease caused by two basidiomycete fungi belonging to the genus Crinipellis (Agaricales), both of which are currently on an invasive front Classical biological control, in which coevolved natural enemies are considered to offer the most potential for sustainable control of invasive alien organisms, is investigated as a management strategy Our initial approach has been to search for the suspected coevolved host (Theobroma gileri) of one of these pathogens, Crinipellis roreri, the causal agent of frosty pod rot, in the mesic forests of north-west Ecuador; to isolate the endophytes and mycoparasites associated with both host and pathogen; to screen selected fungi in the greenhouse and laboratory, in order to determine their biocontrol potential Endophytes were isolated directly in the field from healthy tree boles and pods, and over 40 genera were recorded, mainly representing anamorphs of Hypocreales in the genera Acremonium, Clonostachys, Trichoderma and Verticillium, as well as basidiomycetes belonging to the Agaricales and Polyporales Of the endophytic fungi tested, most can be inoculated into and recovered from asymptomatic cocoa seedlings Twenty-eight mycoparasitic species were isolated from diseased pods and selected mycoparasites as well as endophytes were screened against C roreri using the pre-colonised plate method Consistently high mycoparasitism of the C roreri pseudostroma was demonstrated, particularly by a complex of Clonostachys and Trichoderma species

Are invasives bigger? a global study of seed size variation in two invasive shrubs

Abstract: We explored the spatial structure of seed size variation and tested whether seed size differed between native and exotic populations in two invasive species. Seed of Cytisus scoparius (Scotch broom) is significantly heavier in its exotic range, whereas seed of Ulex europaeus (European gorse) is no different between ranges. This result suggests that seed size in C. scoparius is either adaptively or phenotypically responsive to conditions in its exotic range or that plants with large seeds were preferentially introduced. We found that modern ornamental broom seed was no bigger than seed from natural or naturalized populations, suggesting that large seed size in the exotic range is not due to preferential introduction of ornamental varieties with large seeds. Most previous studies of trait differences between native and exotic ranges in invasive species have not taken variation throughout the ranges into account. This is the most comprehensive survey of seed size variation in any species, and the first time that variation in a trait of an invasive species has been studied from individual plant level up to global ranges. Demographic rates can be affected by seed attributes making this study an important first step in understanding how population processes may differ between native and exotic ranges.

Effects of host plant drought stress on the performance of the bird cherry‐oat aphid, Rhopalosiphum padi (L.): a mechanistic analysis

Abstract: 1. The growth (increase in height and leaf number) of four grass species was reduced by a -0.5 MPa drought stress, but the performance of an associated herbivore, Rhopalosiphum padi (L.), was not affected consistently. The intrinsic rate of increase of R. padi was reduced by drought stress on three grass species, including Dactylis glomerata (L.), but was unaffected on Arrhenatherum elatius (L.). Therefore, there is no general relationship in the effect of plant drought on an insect herbivore, even among closely related host plant species. 2. Drought stress increased the quality of plant phloem sap, as indicated by increased sieve element osmotic pressure and essential amino acid concentrations. Thus, diet quality could not account for the reduced performance of R. padi under drought stress. The concentration of essential amino acids in the phloem of well-watered A. elatius was, however, lower than that of well-watered D. glomerata, correlating with the decreased performance of aphids on well-watered A. elatius. 3. There were no differences in aphid feeding duration between watering treatments or plant species but sap ingestion rates were reduced significantly under drought stress. 4. Using the measure of dietary amino acid concentrations and the estimate of sap ingestion, the essential amino acid flux through aphids was calculated. Compared with the flux through aphids feeding on well-watered D. glomerata, there was a reduction in aphids feeding on drought-stressed D. glomerata and drought-stressed A. elatius due to lower sap ingestion rates. The flux through aphids on well-watered A. elatius was also reduced due to low phloem essential amino acid concentrations. Thus, the performance of an aphid is correlated with the availability and accessibility of essential amino acids.

Evolutionary Relationships among Aspergillus Species Producing Economically Important Mycotoxins

Abstract: Summary Several mycotoxins are produced by aspergilli, which contaminate our foods and feeds. Economically the most important of these mycotoxins are aflatoxins, ochratoxins and patulin. Recent studies indicate that these compounds can be produced by a number of unrelated Aspergillus species. Evolutionary relationships among sections involving these mycotoxin producing species (Aspergillus sections Circumdati, Flavi, Nigri, Fumigati and Clavati) were evaluated using phylogenetic analysis of -tubulin and ribosomal RNA gene sequences. Phylogenetically unrelated species were found to produce the same mycotoxins. For example, aflatoxins have been produced under laboratory conditions by species belonging to three different sections, while ochratoxin A (OA) and patulin have been produced by a variety of unrelated species. Based on this observation, mycotoxin-producing abilities of the isolates were lost (or gained) several times during the evolution of the genus. Previous studies revealed that biosynthetic genes of several mycotoxins are clustered in the genome, leading to the idea that these clusters could be horizontally transferred as a unit to unrelated species, leading to the biosynthesis of the same mycotoxins in phylogenetically unrelated fungi. Such a mechanism could also explain the widespread occurrence of ochratoxin and patulin production in aspergilli. The organisation of biosynthetic genes of patulin and ochratoxins is unknown. Research is in progress in our laboratory to clarify the genetic background of biosynthesis of these mycotoxins, and to develop biosynthetic gene based probes for the molecular detection of these mycotoxin-producing organisms.

Phylogeny of the frosty pod rot pathogen of cocoa

Abstract: Morphological, cytological and molecular evidence is presented which confirms that the frosty pod rot pathogen of cocoa, formerly classified as the mitosporic fungus Moniliophthora roreri (Deuteromycota), belongs to the hymenomycetous genus Crinipellis (Basidiomycota) and that two varieties should now be recognized: Crinipellis roreri var. roreri and the new variety C. roreri var. gileri. The latter was collected on Theobroma gileri, an endemic tree of submontane forests in north-west Ecuador, and can be distinguished from Ecuadorian and Peruvian isolates from cocoa (T. cacao) on the basis of spore morphology, incompatibility and nucleotide sequence data. As with var. roreri, meiosis is shown to occur within the dispersive and infective spore stage of var. gileri and these meiospores are interpreted to represent a much modified probasidium. In addition, in a field inoculation experiment, an isolate from T. gileri proved to be noninfective to cocoa pods when compared with positive control strains isolated from T. cacao in western Ecuador and T. bicolor in eastern Ecuador. It is concluded that var. gileri is the vestigial progenitor of the frosty pod rot pathogen of cocoa, with a host range and distribution restricted to T. gileri in the mesic forests of north-west South America.

Culture collections over the world

Abstract: Culture collections have the crucial role of providing the authenticated biological material upon which high quality research is based. Importantly, they serve as repositories for strains as part of patent deposits, providers of safe and confidential services to store key organisms for research and industry, and sources of organisms cited in scientific papers that can be used in the confirmation of results and for further study. The demands upon culture collections change as new technologies and uses of organisms are discovered. Many are becoming Biological Resource Centres, as defined by the OECD Biological Resource Centre (BRC) Initiative, in that they operate according to international quality criteria, carry out essential research, enhance the value and applications of strains and provide a vital information resource. In a changing international scientific environment, many collections are under threat of extinction because of inadequate funding, changing government support strategies and the cost of new technologies. We are also suffering a decline in the number of biosystematists, who are needed to form a sound base for molecular technologies and to aid in identifying, and characterizing microbial diversity. In this environment, collections must work together to make the best use of new technologies and to contribute to the description of the 1.4 million fungi yet to be discovered. At the current rate, this will take 700 years. New technologies and novel ways of funding this task must be engaged and, above all, scientists must collaborate. Common policies are necessary to address the regulatory demands on collections, to control access to dangerous organisms, and, in particular, to enforce the Convention on Biological Diversity. Countries that hold the majority of biodiversity require support in building the facilities required to explore their hidden resource. The World Federation for Culture Collections (WFCC) and, in Europe, the European Culture Collection Organisation (ECCO) have a key role to play. The world must benefit from its microbial diversity, which is crucial to solving increasing problems in food provision, public health and poverty alleviation.

The use of amplified fragment length polymorphism for molecular analysis of Beauveria bassiana isolates from Kenya and other countries, and their correlation with host and geographical origin.

Abstract: Beauveria spp. (one Beauveria sp., two B. brongniartii, and 47 B. bassiana) isolated from insects and soil from Kenya and other 16 different countries, were obtained from the CABI Bioscience Genetic Resource Collection. DNA was extracted from the 50 isolates and their genetic variability was investigated using restriction analysis of the internal-transcribed-spacer ribosomal region restriction fragment length polymorphism (ITS-RFLP), ITS sequencing, and amplified fragment length polymorphism (AFLP). The B. bassiana isolates could not be distinguished by ITS-RFLP as all of them showed the same banding pattern. However, the AFLP technique provided more information on polymorphism between the isolates, allowing them to be clustered by relative similarity using band matching and unweighted pair group method with arithmetic mean analysis. Although no significant correlation between the isolates and host and geographical origins were observed, the technique revealed clonal populations of B. bassiana within Kenya.

Genotype and temperature influence pea aphid resistance to a fungal entomopathogen

Abstract: The influence of temperature on life history traits of four Acyrthosiphon pisum clones was investigated, together with their resistance to one genotype of the fungal entomopathogen Erynia neoaphidis . There was no difference among aphid clones in development rate, but they did differ in fecundity. Both development rate and fecundity were influenced by temperature, but all clones showed similar responses to the changes in temperature (i.e. the interaction term was nonsignificant). However, there were significant differences among clones in susceptibility to the pathogen, and this was influenced by temperature. Furthermore, the clones differed in how temperature influenced susceptibility, with susceptibility rankings changing with temperature. Two clones showed changes in susceptibility which mirrored changes in the in vitro vegetative growth rate of E. neoaphidis at different temperatures, whereas two other clones differed considerably from this expected response. Such interactions between genotype and temperature may help maintain heritable variation in aphid susceptibility to fungal pathogen attack and have implications for our understanding of disease dynamics in natural populations. This study also highlights the difficulties of drawing conclusions about the efficacy of a biological control agent when only a restricted range of pest genotypes or environmental conditions are considered.

Why does the larval integument of some sawfly species disrupt so easily? The harmful hemolymph hypothesis

Abstract: The larvae of several sawfly species belonging to the Tenthredinidae (Hymenoptera) have such a low mechanical resistance in the integument that slight mechanical damage to the integument is enough to provoke the release of hemolymph at a given spot We quantified this phenomenon, which we call "easy bleeding", by measuring the pressure needed to pierce dissected sawfly integument We also investigated the feeding deterrence of ethanolic extracts of the hemolymph by laboratory bioassays using Myrmica rubra ant workers These traits, integument resistance and hemolymph deterrence, were inversely related, considering 22 tenthredinid species A negative correlation was obtained by only taking into account the species of one tenthredinid tribe, namely the Phymatocerini (nine species studied) Our results support the "harmful hemolymph hypothesis" that we present here and that assumes a functional link between these morphological and chemical traits, jointly acting as a chemical defense strategy We suspect hemolymph deterrence to be often due to sequestration of plant secondary metabolites We discuss the role of easy bleeding, considering the fact that sawfly larvae are frequently the prey of invertebrate and vertebrate predators It is suggested that invertebrates such as ants were more important than vertebrates in the evolution of easy bleeding

Going Public: A New Extension Method

Abstract: Contemporary agricultural extension uses intensive face-to-face communication, especially for teaching farmers about pest and disease management. Development scholars are increasingly concerned about the cost of these programmes, and some are trying to reach more farmers through mass media. Small media is another recent option. We have developed a novel method of face-to-face extension, which we call Going Public. It makes use of places where farmers meet spontaneously, such as markets, bus terminals and other public places, to create a two-way learning channel. Going Public allows scientists, extensionists and farmer experts to show things to people, answer questions, run short experiential learning exercises and potentially to distribute material, as in any other face-to-face method, but it is quick and it allows contact with people from many areas at once. It also allows scientists to gather feedback from farmers in a social setting where the farmers are comfortable, surrounded by their friends and nei...

Characterization of phytoplasmas detected in Chinaberry trees with symptoms of leaf yellowing and decline in Bolivia

Abstract: Polymerase chain reaction (PCR) assays were used to detect phytoplasmas in foliage samples from Chinaberry (Melia azedarach) trees displaying symptoms of yellowing, little leaf and dieback in Bolivia. A ribosomal coding nuclear DNA (rDNA) product (1·8 kb) was amplified from one or more samples from seven of 17 affected trees by PCR employing phytoplasma-universal rRNA primer pair P1/P7. When P1/P7 products were reamplified using nested rRNA primer pair R16F2n/R16R2, phytoplasmas were detected in at least one sample from 13 of 17 trees with symptoms. Restriction fragment length polymorphism (RFLP) analysis of P1/P7 products indicated that trees CbY1 and CbY17 harboured Mexican periwinkle virescence (16SrXIII)-group and X-disease (16SrIII)-group phytoplasmas, respectively. Identification of two different phytoplasma types was supported by reamplification of P1/P7 products by nested PCR employing X-disease-group-specific rRNA primer pair R16mF2/WXint or stolbur-group-related primer pair fSTOL/rSTOL. These assays selectively amplified rDNA products of 1656 and 579 bp from nine and five trees with symptoms, respectively, of which two trees were coinfected with both phytoplasma types. Phylogenetic analysis of 16S rDNA sequences revealed Chinaberry yellows phytoplasma strain CbY17 to be most similar to the chayote witches’-broom (ChWBIII-Ch10) agent, a previously classified 16SrIII-J subgroup phytoplasma. Strain CbY1 resembled the Mexican periwinkle virescence phytoplasma, a 16SrXIII-group member. The latter strain varied from all known phytoplasmas composing group 16SrXIII. On this basis, strain CbY1 was assigned to a new subgroup, 16SrXIII-C.

Mycotoxin production and evolutionary relationships among species of Aspergillus section Clavati.

Abstract: Aspergillus clavatus is a commonly encountered fungus in the environment, producing a number of mycotoxins including patulin, kojic acid, cytochalasins and tremorgenic mycotoxins. A. clavatus belongs to Aspergillus section Clavati together with six other species, all of which possess clavate-shaped vesicles. Patulin production was analysed by thin layer chromatography and high performance liquid chromatography, while a primer pair developed for the detection of an iso-epoxydon dehydrogenase gene involved in the biosynthesis of patulin in penicillia was used to detect the ability of patulin production in the isolates examined. A good correlation was observed between patulin producing properties, and the presence of an iso-epoxydon dehydrogenase gene fragment among the isolates tested. A. longivesica was found for the first time to produce patulin. Ribotoxin production was also examined using a PCR-based approach. Ribotoxins were detected for the first time in an A. pallidus and a Hemicarpenteles acanthosporus isolate. A phylogenetic analysis of intergenic transcribed spacer sequence data indicated that most isolates belong to two main clades that have also been identified earlier based on 26 S rDNA sequence data. A. pallidus isolates clustered together with A. clavatus strains. Although A. clavatus isolates produced highly homogeneous random amplified polymorphic DNA profiles, phylogenetic analysis of these data let us cluster A. clavatus isolates into distinct clades. Correlations were not observed between either patulin or ribotoxin production, and the taxonomic position of the isolates tested, indicating that patulin and ribotoxin producing abilities were lost several times during evolution of Aspergillus section Clavati. Although patulin was earlier found to inhibit mycovirus replication, one of the mycovirus carrying isolates also produced patulin, and both carried the iso-epoxydon dehydrogenase gene.

Molecular mapping of genes conferring field resistance to South American Leaf Blight (Microcyclus ulei) in rubber tree

Abstract: The South American Leaf Blight (SALB), caused by the fungus Microcyclus ulei, is the major rubber tree disease in all Central and South America. A population of 192 progeny individuals derived from a cross between a resistant clone and a susceptible cultivated clone was planted in a field trial in French Guiana in order to evaluate the resistance parameters under real infestation conditions. The resistance type (RT), the presence of stromata (ST) and the level of attack (AT) were observed 20-times on a 22-months period, and semi-quantitative evaluation of stromata was registered only once. The search for QTLs was performed using the Kruskal-Wallis test, Interval Mapping and the Composite Interval Mapping method. One major QTL located on linkage group g13 was detected on the RO 38 map, responsible for 36 to 89% of the phenotypic variance of resistance. This resistance QTL corresponds to one that had previously been detected under controlled conditions of infestation and we called it M13-1bn. Surprisingly, the effect of this QTL was larger under natural conditions of infestation than under controlled inoculation. Other minor QTLs (four on the RO38 map and one on the PB 260 map) were also detected. The type of resistance brought by M13-1bn, as well as its durability, are discussed. Applications for rubber tree breeding programs are considered.

Molecular Characterization of Tomato and Chili Leaf Curl Begomoviruses from Pakistan.

Abstract: Leaf curl or yellowing symptoms, typical of those caused by begomovirus infection, are commonly observed in chili (Capsicum annuum) and tomato (Lycopersicon esculentum) plantings in Pakistan. One chili sample with leaf curl symptoms was collected in 1998 in Multan (Punjab Province), and two tomato samples with leaf curl and yellowing symptoms were collected from Islamabad and Dargai (North West Frontier Province) in 2000 and 2001, respectively. Virus DNA was first amplified by polymerase chain reaction using the degenerate primer pair PAL1v1978/PAR1c715 (3). The expected 1.4-kb PCR products were obtained from the three samples. Based on the sequences of the 1.4-kb DNA products, specific primers were designed to complete each of the DNA-A sequences. Two primer pairs, DNABLC1/DNABLV2 and DNABLC2/DNABLV2, were used for the detection of DNA-B (2). The genome of the tomato leaf curl isolate from Islamabad contained a DNA-A of 2,739 nucleotides (GenBank Accession No. AF448059), a DNA-B of 2,728 nucleotides (GenBank Accession No. AY150304), and had 94% nucleotide identity in the common region. The genome of the tomato leaf curl isolate from Dargai contained a DNA-A of 2,740 nucleotides (GenBank Accession No. AF448058), a DNA-B of 2,686 nucleotides (GenBank Accession No. AY150305), and had 96% nucleotide identity in the common region. Each of the tomato isolates contained eight predicted open-reading frames (ORFs) (AV1, AV2, AV3, AC1, AC2, AC3, AC4, and AC5) in the DNA-A and two predicted ORFs (BV1 and BC1) in the DNA-B. The DNA-A nucleotide sequence identity of the Islamabad isolate and Dargai tomato isolate is 96% and that of DNA-B is 88%. Sequence comparisons with begomovirus sequences available in the GenBank sequence database showed that these two tomato virus isolates had the highest sequence identity with Tomato leaf curl New Delhi virus-Severe (GenBank Accession No. U15015) from northern India (more than 95% for DNA-A and less than 90% for DNA-B). The DNA-A of the virus associated with chili leaf curl from Pakistan (GenBank Accession No. AF336806) consists of 2,754 nucleotides, containing six predicted ORFs (AV1, AV2, AC1, AC2, AC3, and AC4). The chili virus was unrelated to the two tomato begomovirus isolates from Pakistan, with which it shares less than 75% nucleotide identity. Sequence comparisons show highest sequence identity (87%) with Tomato leaf curl Bangladesh virus (GenBank Accession No. AF188481). DNA-beta of 1.3 kb was detected in the chili begomovirus isolate using Beta01/Beta02 primers (1). There was no evidence for the presence of a DNA-B in the chili begomovirus isolate when tested by the two DNA-B specific primer pairs. Based on DNA sequence comparisons, the chili leaf curl virus from Pakistan, to our knowledge, constitutes a distinct, new monopartite begomovirus. References: (1) R. W. Briddon et al. Mol. Biotechnol. 20:315, 2002. (2) S. K. Green et al. Plant Dis. 85:1286, 2001. (3) M. R. Rojas et al. Plant Dis. 77:340, 1993.

Steinernema weiseri n. sp. (Rhabditida, Steinernematidae), a new entomopathogenic nematode from Europe

Abstract: Steinernema weiseri n. sp. is described from a roadside with apple trees near Ceske Budejovice, Czech Republic. The species is also widely distributed in Germany and Slovakia, from where it had previously been reported as Steinernema spec. F. The British Steinernema sp. D1 is considered conspecific with S. weiseri n. sp. Males of the new species are mainly characterised by light brown, slightly curved spicules with a long manubrium and the presence of a short tail mucron in the second generation. Third-stage infective juveniles are characterised by a `medium size' body and tail length, short hyaline tail portion (mostly around 1/3 of tail length), the excretory pore situated in the mid-pharynx region, lip region slightly offset, angular and flattened, and the lateral field having nine equally developed lines separated by eight distinct ridges. S. weiseri n. sp. is most similar to S. feltiae, with which it did not hybridise. RFLP analysis of the ITS region of the rDNA repeat shows S. weiseri n. sp. to be distinct from 50 other Steinernema species and isolates. The new species was found in a wide range of habitats and is readily maintained on Galleria mellonella larvae.

Inter- and intraspecific morphometric variation and characterization of Phytophthora isolates from cocoa

Abstract: Difficulties in the accurate identification of the Phytophthora species responsible for black pod disease of cocoa continue to hamper effective disease control. A re-evaluation of morphological characters (Brasier & Griffin, 1979) and a detailed morphometric analysis of 161 Phytophthora isolates largely associated with black pod disease of cocoa from 17 countries worldwide have shown considerable inter- and intraspecific variation. Stable and more reliable parameters for the identification of the species responsible for the disease have been determined. Colony characteristics such as pattern and growth rate on V8 agar are reasonably characteristic for the cocoa Phytophthora species, and can be used to make preliminary identification to species level. Significant sporangial character variation was found within isolates of species from the same and different sources, highlighting the difficulties in making accurate identification on the basis of raw morphological data. Pedicel length was found to be the most consistent species-linked sporangial characteristic. Cluster plots of length/breadth ratios of sporangia versus reciprocals of sporangial pedicel length clearly separated all isolates into distinct species groups (P. capsici, P. citrophthora, P. palmivora and P. megakarya) and can be used reliably to identify accurately those pathogens involved in black pod disease outbreaks.

Pyrrolizidine alkaloid content in Senecio: ontogeny and developmental constraints.

Abstract: The ontogeny of pyrrolizidine alkaloid (PA) synthesis and constraints on defence level during the seedling stage were examined in the annual Senecio vulgaris and the monocarpic perennial Senecio jacobaea In both species, PAs were actively synthesized from the onset of seedling growth so that juvenile stages did not go through an undefended stage Roots are known to be the exclusive sites where PAs are produced Root biomass was the single most important biomass parameter explaining variation in total PAs per seedling All correlation coefficients between—relative growth rate and PA concentration were negative, but none was significant However, a significant negative—correlation was found between shoot to root ratio and PA concentration in S jacobaeaseedlings, suggesting a dilution effect of the PAs Earlier studies have shown that the shoot to root ratio is positively correlated with relative growth—rate of established S jacobaea plants It is therefore suggested that young S jacobaea plants with a high shoot to root ratio and hence a high growth capacity necessarily have lower PA defence levels than plants with a low shoot to root ratio

Actual and potential distribution of an invasive canola pest, Meligethes viridescens (Coleoptera: Nitidulidae), in Canada

Abstract: Meligethes viridescens (Fabricius), le coleoptere des fleurs du colza, est un ravageur commun de colza oleagineaux [Brassica napus L. et Brassica rapa L. (Brassicaceae)] dans la sous-region de l'ouest palearctique. L'etablissement de M. viridescens dans l'est de l'Amerique du Nord suscite des inquietudes parce qu'il represente un risque pour l'industrie de colza du Canada ou l'on cultive jusqu'a 4 millions d'hectares de colza d'ete, B. napus et B. rapa, chaque annee. L'etude de specimens de musee indique que M. viridescens est d'abord apparu en Nouvelle-Ecosse en 1947. Les etudes sur le terrain ont demontre qu'en 2001, M. viridescens a progresse vers l'ouest jusqu'a Saint-Hyacinthe, Quebec. Un modele CLIMEX MD a ete elabore et valide en Europe avec des donnees sur la repartition reelle de M. viridescens. Au Canada, le modele predit qu'une fois introduit, le ravageur peut facilement survivre dans les zones de culture de colza. La repartition actuelle de M. viridescens dans l'est du Canada correspond bien a la repartition predite par le modele. La dispersion vers l'ouest et l'etablissement de M. viridescens dans les zones de culture de colza de l'Ontario et de l'ouest canadien, particulierement dans le sud du Manitoba, semblent inevitables. La colonisation de ces regions pose un risque de pertes considerables pour les producteurs de colza.

Molecular relatedness within the "Ascochyta pinodes-complex"

Abstract: The morphological, molecular and pathological characters of 34 isolates identified as Ascochyta pinodes, A. phaseolorum, and Phoma medicaginis var. pinodella were determined. Initial molecular findings, based on PCR fragment size and RFLPs of sections of the mitochondrial genome, the rRNA gene cluster and the β-tubulin gene complex, were further investigated by sequencing of the total rRNA ITS regions. Isolates were homogenous for all characteristics determined, with the exception of conidial size and septation, and RFLPs of AT rich (presumptive mitochondrial) DNA. The results suggest that the isolates represent host preferential forms of a single taxon, and this finding is discussed in relation to the known teleomorphs and reference material of the species studied.