1,721,044 research outputs found
Perspectives for integrated insect pest protection in oilseed rape breeding
Full text linkIn the past, breeding for incorporation of insect pest resistance or tolerance into cultivars for use in integrated pest management schemes in oilseed rape/canola (Brassica napus) production has hardly ever been approached. This has been largely due to the broad availability of insecticides and the complexity of dealing with high-throughput phenotyping of insect performance and plant damage parameters. However, recent changes in the political framework in many countries demand future sustainable crop protection which makes breeding approaches for crop protection as a measure for pest insect control attractive again. At the same time, new camera-based tracking technologies, new knowledge-based genomic technologies and new scientific insights into the ecology of insect–Brassica interactions are becoming available. Here we discuss and prioritise promising breeding strategies and direct and indirect breeding targets, and their time-perspective for future realisation in integrated insect pest protection of oilseed rape. In conclusion, researchers and oilseed rape breeders can nowadays benefit from an array of new technologies which in combination will accelerate the development of improved oilseed rape cultivars with multiple insect pest resistances/tolerances in the near future
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Das von Duftstoffen vermittelte Wirtsfindungsverhalten des Ektoparasitoiden Holepyris sylvanidis und seine Relevanz für die biologische Bekämpfung von Vorratsschädlingen
No full textThis thesis focused on the semiochemicals mediating host-searching behavior of the ectoparasitoid Holepyris sylvanidis (Hymenoptera: Bethylidae) which attacks larvae of various stored-product pest beetles, especially those of the confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae). Prior to this thesis, it was already known that the parasitoid uses host-specific compounds released from larval feces of T. confusum for host location and that the attractiveness of host-specific kairomones for the parasitoid increases by the addition of habitat background odor. Moreover, host cuticular hydrocarbons (CHCs) serve as contact kairomones for host recognition by H. sylvanidis and mediate trail-following behavior in foraging parasitoids, but only for a period of two days. Despite these initial findings, many chemical and ecological aspects of the parasitoid’s host search and the potential of host-specific kairomones to enhance biological control were still poorly understood.
Therefore, the goal of this thesis was to gain deeper insights in the chemically mediating host search of H. sylvanidis. Various behavioral bioassays and chemical analysis of host kairomones via coupled gas chromatography-mass spectrometry were performed to answer the following questions:
(i) Which factors drive the loss of kairomonal activity of host larval CHC trails over time? (Chapter 2)
(ii) Do H. sylvanidis females discriminate a host from a non-host species based on a host-specific CHC pattern present on the cuticle? (Chapter 3)
(iii) Does the additional application of host-specific kairomones improve the host search activity of the parasitoid and thus, its efficiency in controlling T. confusum? (Chapter 4).
In Chapter 2, we first investigated whether the time-limited kairomonal activity of host trails was due to changes in the CHC composition induced by microbes. Chemical analysis revealed that the CHC profile of host trails did not change qualitatively or quantitatively over a two-day period regardless of whether they were analyzed under sterile or non-sterile conditions. These results prompted the suggestion that factors other than microbial degradation might determine the temporary behavioral activity of CHC trails. This assumption was confirmed by our cryo-scanning electron microcopy results. Within two days, host trails gradually formed solid microstructures most likely due to a self-assembly of CHCs. But this process was reversible by hexane application which in turn led to the recovery of kairomonal activity of two-day-old CHC trails. Parasitoids followed these re-activated host trails as they did when encountering freshly laid ones. Our results suggest that the gradual solidification of long-chain CHCs in a host trail over time reduces the perceptibility for H. sylvanidis as such that the trail is no longer followed.
In Chapter 3 we examined the influence of different CHC profiles of three closely related and one distantly related beetle species on the host recognition behavior of H. sylvanidis. In bioassays the parasitoid successfully recognized and accepted larvae of Tribolium spp. as hosts, whereas larvae of Oryzaephilus surinamensis were rejected. The latter species elicited a behavioral response in H. sylvanidis only when solvent extracted larvae were treated with a sample of T. confusum larval CHCs. Chemical analysis of larval extracts showed that the CHC profiles of the host and non-host species differed in their compositions. The main difference was the presence of methylated alkanes (MeAL) on the cuticle of Tribolium spp. and the absence of MeAL on that of O. surinamensis. MeAL serve as host recognition cues that enable the parasitoid to distinguish a host from a non-host species.
In Chapter 4, we first examined whether volatiles associated either to T. confusum larvae or to other host stages (e.g., beetle adults) participate in the host search of H. sylvanidis over long distances. The parasitoid was most attracted to a mix of two larval key compounds (2CM = (E)-2-nonenal and 1-pentadecene) emitted from larval feces, but the behavioral response of the parasitoid was concentration dependent. In contrast, volatiles released by T. confusum adults were not attractive for the parasitoid in all concentrations tested. We then studied whether the additional presence of synthetic 2CM (in the most attractive concentration) has an enhancing effect on the host search of H. sylvanidis. In three-day lasting flight cage experiment we offered T. confusum larvae either with additionally applied 2CM (test) or without (control) to parasitoid females. In test cages, parasitoids removed significantly more beetle larvae from the initial population within 48 h and parasitized a significantly higher number of host larvae after 72 h compared to those in the control cages. Furthermore, significantly more parasitoid offspring emerged from host larvae parasitized in the presence of 2CM. However, the increasing population size in the F1 was due to a significant increase in male offspring. These results illustrate that the host-finding success and parasitization rate of parasitoids can be improved by the additional release of host-specific, synthetic kairomones. But this is associated with changes in the population composition (male/female) of the parasitoid progeny.
Overall, the results obtained in this thesis on the semiochemicals mediating host-searching behavior of a natural antagonist of stored-product pest beetles contribute to a better understanding of the interaction between parasitoids and their host species. In addition, they provide important insights into the potential use of host-associated, behaviorally modifying compounds to increase the efficiency of parasitoids in the biological control of insect pests in storage environments.Diese Doktorarbeit befasste sich mit der durch Semiochemikalien vermittelten Wirtssuche des Ektoparasitoiden Holepyris sylvanidis (Hymenoptera: Bethylidae), der die Larven verschiedener vorratsschädlicher Käfer parasitiert, aber die des amerikanischen Reismehlkäfers Tribolium confusum (Coleoptera: Tenebrionidae) bevorzugt. Vor dieser Arbeit war bereits bekannt, dass sich der Parasitoid bei der Wirtssuche anhand von Duftstoffen orientiert, die aus dem Larvalkot von T. confusum stammen, und dass die Attraktivität dieser wirtsspezifischen Kairomone für den Parasitoiden durch den Habitatduft (ausgehend von Futtersubstrat des Schädlings; hier Weizenvollkornschrot) verstärkt wird. Zudem dienen kutikuläre Kohlenwasserstoffe (KKW) der Wirtslarven als Kontaktkairomone zur Wirtserkennung und lösen Spurfolgeverhalten im Parasitoiden aus, aber nur über einen Zeitraum von zwei Tagen. Trotz dieser ersten Ergebnisse waren viele chemische und ökologische Aspekte der Wirtssuche von H. sylvanidis und das Potenzial wirtsspezifischer Kairomone zur Verbesserung der biologischen Schädlingsbekämpfung im Vorratsschutz weiterhin unbekannt.
Daher war es das Ziel dieser Arbeit, tiefere Einblicke in die chemisch vermittelte Wirtssuche von H. sylvanidis zu gewinnen. Verschiedene Verhaltensversuche und chemische Analysen von Wirtskairomonen mittels gekoppelter Gaschromatographie-Massenspektrometrie wurden durchgeführt, um die folgenden Fragen zu beantworten:
i) Welche Faktoren tragen dazu bei, dass die Aktivität der KKW-basierten Kairomone der Wirtsspuren nach drei Tagen verloren geht? (Kapitel 2)
ii) Unterscheiden die Weibchen von H. sylvanidis eine Wirtsart von einer Nichtwirtsart anhand eines wirtsspezifischen KKW-Musters auf der Kutikula? (Kapitel 3)
iii) Kann die zusätzliche Ausbringung von wirtsspezifischen Kairomonen das Wirtssucheverhalten des Parasitoiden fördern und somit zu einer effektiveren Bekämpfung von T. confusum führen? (Kapitel 4)
Im zweiten Kapitel untersuchten wir zuerst, ob die zeitlich begrenzte kairomonale Aktivität der Wirtsspuren möglicherweise auf durch Mikroorganismen verursachte Veränderungen in der Zusammensetzung des KKW-Profils zurückzuführen ist. Jedoch zeigten chemische Analysen, dass sich die KKW-Profile der Wirtsspuren weder qualitativ noch quantitativ in einem Zeitraum von zwei Tagen veränderten, unabhängig davon, ob diese unter sterilen und nicht-sterilen Bedingungen analysiert wurden. Diese Ergebnisse deuteten darauf hin, dass nicht der mikrobielle Abbau, sondern andere Faktoren für die temporäre, spurfolgeauslösende Aktivität der KKW verantwortlich sein könnten. Diese Annahme wurde durch unsere Untersuchungen am Rasterelektronenmikroskop bestätigt. Innerhalb von zwei Tagen bildeten die Wirtspuren feste Mikrostrukturen, höchstwahrscheinlich aufgrund einer Selbstaggregation der KKW. Diese Prozesse waren jedoch durch die Zugabe von Hexan umkehrbar, sodass die kairomonale Aktivität von zwei Tage alten Wirtsspuren wiederhergestellt werden konnte. Der Parasitoid folgte diesen reaktivierten Wirtspuren im gleichen Maße, wie bei frisch gelegten Wirtsspuren. Basierend auf diesen Ergebnissen ist es sehr wahrscheinlich, dass die Verfestigung von langkettigen KKW in einer Wirtsspur die Wahrnehmbarkeit für H. sylvanidis im Laufe der Zeit so weit verringert, dass kein Spurfolgeverhalten mehr ausgelöst werden kann.
Im dritten Kapital untersuchten wir den Einfluss unterschiedlicher KKW-Profile von drei engverwandten Wirtsarten und einer entfernt verwandten Käferart auf das Wirtserkennungsverhalten von H. sylvanidis. In Verhaltensversuchen erkannten und akzeptierten weibliche Parasitoide die Larven der Tribolium-Arten als Wirte, während Larven von Oryzaephilus surinamensis abgelehnt wurden. Eine Veränderung im Verhalten des Parasitoiden konnten O. surinamensis-Larven nur auslösen, wenn lösungsmittelextrahierte Larven mit einem von T. confusum-Larven stammenden KKW-Extrakt behandelt wurden. Chemische Analysen der Larvenextrakten zeigten, dass sich die KKW-Profile der Wirtsarten und der Nicht-Wirtsart in ihrer Zusammensetzung unterschieden. Dies war vor allem auf die Fraktion der methylverzweigten Alkane (MeAL) zurückzuführen. Diese Verbindungen kamen auf der Kutikula von Tribolium spp. vor, fehlten aber bei O. surinamensis. Folglich dienen MeAL als Kontaktkairomone für die Wirtserkennung, anhand derer der Parasitoid eine Wirtsart von einer Nicht-Wirtsart unterscheidet.
Im vierten Kapitel untersuchten wir, ob flüchtige Duftstoffe, die entweder direkt mit T. confusum-Larven oder mit anderen Wirtsstadien (z.B. adulten Käfern) assoziiert sind, an der Wirtsfindung von H. sylvanidis aus größerer Entfernung beteiligt sind. Der Parasitoid wurde am stärksten von einem Mix aus zwei Schlüsselkomponenten aus dem Duftstoffbouquet des Larvenkots von T. confusum (z.B. (E)-2-nonenal und 1-Pentadecen, 2CM) in der niedrigsten Konzentration angelockt, während die höchste Konzentration abschreckend wirkte. Im Vergleich dazu waren zwei ausgewählte flüchtige Verbindungen, die von T. confusum-Adulten abgegeben werden, in allen Konzentrationen unattraktiv für den Parasitoiden. Anschließend untersuchten wir, ob die zusätzliche Ausbringung von 2CM (in der attraktivsten Konzentration) die Wirtssuche von H. sylvanidis verbessern kann. In dreitägigen Verhaltensversuchen wurden Parasitoiden T. confusum-Larven entweder mit zusätzlich ausgebrachten synthetischen Duftstoffen (= 2CM, Test) oder ohne (Kontrolle) angeboten. Im Vergleich zur Kontrolle entfernten Parasitoidweibchen in den Testkäfigen innerhalb von 48h signifikant mehr Käferlarven aus der Ausgangspopulation und parasitierten bis zum Ende des Versuchs (nach 72h) eine signifikant größere Anzahl an Wirtslarven. Aus den Wirtlarven, die in Gegenwart von zusätzlich ausgebrachtem 2CM parasitiert wurden, schlüpften signifikant mehr Nachkommen von H. sylvanidis. Die Populationszunahme der F1 war jedoch auf einen signifikanten Anstieg männlicher Individuen zurückzuführen. Folglich können der Wirtsfindungserfolg und die Parasitierungs-rate des Parasitoiden durch die Ausbringung synthetischer, wirtsassoziierter Kairomone verbessert werden, was aber mit Veränderungen in der Populations-zusammensetzung (Männchen/ Weibchen) der Nachkommen einhergeht.
Insgesamt tragen die in dieser Dissertation erzielten Ergebnisse zur durch Semiochemikalien vermittelten Wirtssuche eines natürlichen Gegenspielers von vorratsschädlichen Käfern zu einem besseren Verständnis der Interaktion zwischen Parasitoiden und ihren Wirtsarten bei. Darüber hinaus liefern sie wichtige Erkenntnisse über den potenziellen Einsatz von wirtsassoziierten, verhaltensverändernden Verbindungen zur Verbesserung der Wirksamkeit von Parasitoiden bei der biologischen Bekämpfung von Schadinsekten in Vorratslägern und in der verarbeitenden Lebensmittelindustrie
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Environmental metabolomics approaches to identify and enhance secondary compounds in medicinal plants for bio-based plant protection
Full text linkThe use of plant extracts such as essential oils (EOs) as botanical pesticides has numerous advantages, including the high effectiveness against a wide range of diseases and pest insects of agricultural and medicinal importance due to multiple mechanisms of action. EOs belong to secondary plant metabolites, which mediate direct and indirect plant defenses against biotic and abiotic stress conditions. The main objective of this thesis was to obtain plant extracts from aromatic plants, which can be used as bio-based plant protection products. The general hypothesis investigated whether a) the content of biologically active substances of two Iranian medicinal plants species (Ferula assa-foetida and Zataria multiflora) originated from a wide range of extreme environments is correlated with certain environmental factors; whether b) certain secondary plant metabolites from F. assa-foetida and Z. multiflora can be used as biologically active compounds against fungal infestations in crops; and whether c) the production of these metabolites can be artificially increased by mimicking extreme environmental conditions during cultivation.
a) First of all this study evaluated whether environmental factors can be utilized to predict the presence of specific compounds from medicinal plants by two different methods, near-infrared spectroscopy (NIRS) and gas chromatography coupled mass spectrometry (GC−MS). Using an environmental metabolomics approach (GC−MS), on the basis of EOs from roots, three distinct chemotypes were found among 10 Ferula assa-foetida L. populations. These were characterized by (I) monoterpenes and Z-1-propenyl sec-butyl disulfide; (II) eudesmane sesquiterpenoids and α-agarofuran; (III) Z- and E-1-propenyl sec-butyl disulfide. NIRS measurements indicated a similar, but less distinct pattern. Structural equation models (SEMs) showed that EO compounds and content were directly influenced by edaphic factors and temperature (chapter 2).
Essential oil compounds from leaves of 14 populations of Z. multiflora were classified into three main groups, each representing a distinct chemotype with linalool, thymol and carvacrol as the major components. Corresponding to the phytochemical cluster analysis, the hierarchical cluster analysis based on NIR data also recognized the carvacrol, thymol and linalool chemotypes. The SEMs approach revealed direct effects of soil factors and mostly indirect effects of latitude and altitude on EO compounds and content of Z. multiflora populations. Therefore, predicting EO compounds or chemotypes by environmental metabolomics can be used in medicinal plants to select populations with the desired chemical profile (chapter 3).
b) Due to increasing demand of natural compounds for food preservatives and plant pathogen control, plant extracts with bioactive secondary metabolites can be used as an effective and ecofriendly plant protection approach. Hydroalcoholic extracts and EOs of Z. multiflora were assessed to identify biologically active compounds and/or chemotypes against the plant pathogens Fusarium culmorum, Fusarium sambucinum, Botrytis cinerea, Alternaria dauci and Colletotrichum lindemuthianum (chapter 4 and 5).
On the basis of non-volatiles compounds of Z. multiflora hydroalcoholic extracts analyzed by LC−MS, three major chemical classes were found among the 14 populations. A total of 32 metabolites were annotated including flavonoid conjugates, hydroxycinnamic acid derivatives and phenolic terpenes. Flavonoids were the main compounds in the extracts, considering that two third of the annotated compounds represent flavonoid conjugates. The antifungal activity of extracts from Z. multiflora populations showed high variability from weak (≤ 37 %) to high inhibition rates (up to 65 %). Nine compounds such as dihydroquercetin, dihydrokaempferol, naringenin and eriodictyol strongly positively correlated with antifungal activity (chapter 4).
Corresponding to the single volatile compounds, even low concentrations of the carvacrol and thymol, but not of the linalool chemotype EOs inhibited significantly the growth of all fungal pathogens. Bioassays revealed positive correlation between relative amounts of p-cymene, γ-terpinene, thymol and carvacrol and the inhibition of the fungal mycelium growth, whereas myrcene and linalool relative amounts had a strong negative correlation with antifungal activity (chapter 5).
c) To enhance the production of biologically active metabolites, carvacrol and linalool chemotypes of Z. multiflora were cultivated under extreme environmental conditions including UV-A radiation, heat and drought stresses. Although no significant differences were observed in extracted volatile compounds in UV-A irradiated plants, the relative content of linalool was slightly reduced in the linalool chemotype, whilst the relative amount of carvacrol was slightly increased. Drought stress alone did not alter the relative contents of volatile compounds in both chemotypes, whilst high temperatures lead to a decrease of the linalool content and an increase of the relative amount of carvacrol in the linalool chemotype. Furthermore, the interaction of drought and heat induced changes in plants of the linalool chemotype resulting in higher relative amounts of carvacrol and lower relative amounts of linalool. Moreover, the main volatile compounds of plants from the carvacrol chemotype did not change in response to abiotic stresses (chapter 5).
Understanding the effect of environmental conditions on populations and chemotypes of medicinal plants supports the development of natural and sustainable fungicides or insecticides. Although several hypotheses and questions have been developed and tested or answered in this study, further studies are needed to gain deeper insight into the bioactive metabolite biosynthesis of Z. multiflora. We have to study further, how severe stress conditions affect different chemotypes of F. assa-foetida and other medicinal and aromatic plant species
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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