1,721,008 research outputs found
Use of three-way interactions between pests, microbes and plants to protect maize (Zea mays L.) and potato (Solanum tuberosum L.) against soil herbivory
No full textV okviru raziskav doktorske disertacije smo preučevali trosmerne interakcije med rastlinami, mikrobi in žuželkami za zaščito pridelka pred talno herbivorijo. Skupno smo analizirali 71 izolatov gliv iz rodu Metarhizium, Beauveria in Trichoderma z namenom testiranja njihove sposobnosti okužbe ličink rumenega mokarja in hkratnega spodbujanja rasti koruze. Izolata Metarhizium brunneum (1154) in Beauveria bassiana (2121) sta pri mokarjih povzročila največjo smrtnost (100 %). Nekateri izolati, kot je Metarhizium robertsii (2693), imajo potencial za nadaljnje raziskave, saj niso povzročili le visoke smrtnosti mokarjev, temveč so pozitivno vplivali tudi na vse parametre rasti koruze. Z nadaljnjimi laboratorijskimi poskusi smo preučevali učinke entomopatogenih gliv (EPG) na strune, pri čemer je M. brunneum (izolat 1868) značilno povečal smrtnost strun in bil najpogosteje ponovno izoliran iz površine korenin koruze. Poljski poskusi so pokazali, da obdelava zrn koruze z M. brunneum (1868) omogoča višji začetni sestoj koruze pri treh sortah, in pri eni sorti tudi višji končni sestoj koruze. Poskusi testiranja različnih pripravkov na osnovi EPG iz rodu Metarhizium za zatiranje strun so pokazali, da so glive v obliki granul (zlasti pripravek ATTRACAP in formulacija gliv na rižu) povzročile zmanjšanje deleža poškodovanih gomoljev. Prav tako smo ugotovili, da vrsta rastlinske prehrane vpliva na rast in razvoj ličink, ne pa nujno tudi na povečanje občutljivosti za okužbo z EPG. Z olfaktometrom z dvojno izbiro smo raziskovali vedenjski odziv strun na EPG v prisotnosti rastlin koruze. Čeprav je bila koruza ustrezno privabilo, nismo uspeli dokazati repelentnega učinka EPG. Z analizo hiperspektralnih posnetkov v spektralnem območju 400–2500 nm smo s skupno natančnostjo 86,7 % zaznali in razlikovali med biotskim (strune) in abiotskim (suša) stresom pri koruzi in tako potrdili potencial daljinskega zaznavanja za zgodnje odkrivanje suše in/ali napada strun v koruzi.We investigated three-way interactions between plants, microbes and insects. A total of 71 isolates of fungi from the genera Metarhizium, Beauveria and Trichoderma were analysed for their ability to infect yellow mealworm larvae and stimulate maize growth. The isolates Metarhizium brunneum (1154) and Beauveria bassiana (2121) caused the highest mortality (100 %) in mealworms. Some isolates, such as Metarhizium robertsii (2693), showed potential for further research, as it not only caused 73 % mortality of mealworms, but also had a positive effect on all maize growth parameters. In further laboratory experiments, the effects of entomopathogenic fungi (EPF) on wireworms were investigated. It was found that M. brunneum (isolate 1868) significantly increased wireworm mortality and was most frequently reisolated from maize rhizoplane. Field trials have shown that soaking maize kernels in M. brunneum (1868) suspension resulted in a higher initial maize stand in three varieties, wherease in one variety also final maize stand was increased. Trials testing different EPF-based preparations of the genus Metarhizium for wireworm control showed that granular application of fungi (especially ATTRACAP and EPF formulated on rice) caused significant reduction of the proportion of damaged tubers. Plant diet influenced wireworm growth and development, but not necessarily susceptibility to EPF infection. Using a dual-choice olfactometer, we investigated the behavioural response of wireworms to EPF in the presence of maize plants. Although maize was a suitable attractant, we could not detect any repellent effect of EPFs. By analysing hyperspectral images in the spectral range of 400–2500 nm, we detected and discriminated between biotic (wireworms) and abiotic (drought) stress in maize with an overall accuracy of 86,7 %, confirming the potential of hyperspectral imaging for early detection of drought and/or wireworm infestation in maize
Assessment of toxicity of aegerolysin and MACPF-domain protein complexes against cereal leaf beetle and cabbage flea beetle
No full textPotreba po iskanju novih bioinsekticidov je vedno večja. V tej magistrski nalogi smo testirali proteine egerolizinske družine iz bukovega ostrigarja, ki v kombinaciji s pleurotolizinom B, proteinskim partnerjem z domeno MACPF (ang. membrane-attack domain/perforin) deluje insekticidno na koloradskega in koruznega hrošča, ki spadata v družino lepencev (Chrysomelidae). Insekticidno delovanje je posledica vezave egerolizinskega partnerja na membranski sfingolipidni receptor ceramid fosfoetanolamin (CPE), ki je specifičen za nevretenčarje. Da bi preverili, ali so kompleksi na osnovi egerolizinov toksični tudi za druge hrošče iz družine lepencev, smo komplekse egerolizin/pleurotolizin B testirali še na dveh rastlinskih škodljivcih iste družine: na žitnem strgaču (Oulema melanopus) in na kapusovem bolhaču (Phyllotreta atra). Žuželke smo nabrali na netretiranih poljih in nastavili poskus tako, da smo z egerolizini in egerolizinskimi kompleksi obdelali liste, s katerimi so se žuželke prehranjevale. Naši testi so pokazali občutljivost žitnega strgača na izpostavitev proteinom, medtem ko osebki kapusovega bolhača za to niso bili dovzetni. Z analizo lipidnih ekstraktov žuželk smo preverili prisotnost egerolizinskega receptorja CPE pri žitnem strgaču in kapusovem bolhaču kakor tudi pri drugih rastlinskih škodljivcih (marmorirana smrdljivka, plodova vinska mušica, velika žitna uš, koruzni hrošč in koloradski hrošč). Prisotnost CPE smo dokazali v vseh vzorcih, a v različnih koncentracijah. Najvišjo koncentracijo CPE ima plodova vinska mušica, najmanjšo pa velika žitna uš. Primerjava lipidomskih analiz in testov toksičnosti je pokazala, da koncentracija CPE v membranah nima vloge pri delovanju egerolizinov in egerolizinskih kompleksov na žuželke.The need to find new bioinsecticides is continuously increasing. In this MSc thesis, we tested aegerolysin proteins from oyster mushrooms that had been found to exert insecticidal effects against two plant pests that belong to the Chrysomelidae family: the Colorado potato beetle and the Western corn rootworm. These aegerolysins bind to insect-specific membrane sphingolipid receptor ceramide phosphoethanolamine (CPE) and form transmembrane pores in insect cell membranes in concert with their protein partner pleurotolysin B, which bears a membrane-attack complex/perforin (MACPF) domain. In order to check whether these aegerolysin-based protein complexes are toxic also against other beetles from the Chrysomelidae family, we assessed their toxicity against the cereal leaf beetle (Oulema melanopus) and against the cabbage flea beetle (Phyllotreta atra). The insects were collected on non-treated fields and fed with leaves treated with aegerolysins and aegerolysin/pleurotolysin B mixtures. Our tests showed the sensitivity of cereal leaf beetle to these treatments, while cabbage flea beetles were not susceptible. We also analysed the presence of CPE in lipid extracts from cereal leaf beetle and cabbage flea beetle, as well as from other plant pests (brown marmorated stink bug, Drosophila suzukii, English Grain Aphid, Colorado potato beetle and Western corn rootworm). The presence of CPE was confirmed in all pests’ extracts, but in different concentrations. The highest CPE amount was detected in D. suzukii, and the lowest in English Grain Aphid. The comparison of lipidomic data and toxicity tests showed no correlation between the CPE membrane content and the toxic activity of aegerolysin-based complexes on tested insects
The effect of prophage on Bacillus thuringiensis T0131 larvicidal activity against Drosophila suzukii and Galleria mellonella
No full textBakteriofag (fag) GIL01 okužuje bakterijo Bacillus thuringiensis serovar israelensis. Za izolate te bakterije je značilno, da tekom sporulacije lahko sintetizirajo kristalne toksine, ki so larvicidni. Pripravki izolatov te bakterije so najpogosteje uporabljeni biopesticidi na planetu. V večini larvicidnih izolatov te bakterije se nahaja genom faga (profag) GIL01. Fag GIL01 je temperatni fag, ki v primeru poškodb bakterijske DNA preide v litični cikel. V študiji smo uporabili izolat B. thuringiensis serovar israelensis T0131, ki je bil izoliran iz zemlje v Braziliji. V nasprotju z drugimi naravnimi izolati B. thuringiensis serovar israelensis, izolat T0131 nima profaga GIL01. V nalogi smo uspeli pridobiti lizogeni sev T0131-GIL01. To nam je omogočalo analizo ali prisotnost profaga GIL01 v izolatu T0131 vpliva na preživetje ličink voščene vešče (Galleria mellonella) ali ličink plodove vinske mušice (Drosophila suzukii). Z metodami prisilnega hranjenja in subkutanega injiciranja bakterijskih spor nismo uspeli nedvoumno ugotoviti, ali profag GIL01 v izolatu T0131 vpliva na preživetje ličink voščene vešče. Z metodo prisilnega hranjenja pa smo ugotovili, da izolirani fag GIL01 lahko izboljša preživetje voščene vešče. Z dodajanjem spor v gojišče smo ugotovili, da spore sevov T0131, in T0131 z GIL01 v lizogenem ciklu ne vplivajo na stopnjo smrtnosti ali hitrosti razvoja ličink plodove vinske mušice od jajčeca do odrasle muhe.The bacteriophage (phage) GIL01 infects the bacteria Bacillus thuringiensis serovar israelensis. A distinct characteristic of isolates of this bacterium is the fact that they produce larvicidal crystal toxins during sporulation. Commercial products based on different B. thuringiensis isolates are the most used biopesticides in the world. Most isolates of B. thuringiensis serovar israelensis already possess the genome of the phage (prophage) GIL01. Phage GIL01 is a temperate phage, that switches to a lytic cycle, when bacterial DNA damage occurs. In our studies we used the isolate B. thuringiensis serovar israelensis T0131, which was isolated from soil in Brazil. In contrast to most isolates of B. thuringiensis serovar israelensis, T0131 does not include the prophage GIL01. During our study we were able to produce a lysogenic strain T0131-GIL01. This enabled us to investigate whether the presence of GIL01 in T0131 effects the survivability of Galleria mellonella larvae, or the larvae of Drosophila suzukii. Using the methods of forced feeding and subcutaneous injection of bacterial spores, we were not able to determine whether the presence of GIL01 in T0131 effects the survivability of G. mellonella larvae. Forced feeding with pure GIL01 however, significantly increased the survival rate of G. mellonella. By adding spores of T0131 and T0131 with GIL01 in a lysogenic cycle to the growth medium, we determined that none of the tested strains effects the survivability or development time of D. suzukii from egg to adult fly
Nematode dynamics under minimum tillage
No full textAgriculture has transformed over the past centuries dramatically to become highly dependent on non-renewable fossil fuels, synthetic fertilizers and plant protection agents. This often occurs at the cost of soil degradation and soil food web disturbance. Future agriculture must not only be productive but also provide ecosystem services such as carbon sequestration, pest and disease suppression, nutrient cycling and water storage to become sustainable in the long-term. Sustainability is especially fostered by reduced tillage and the presence of a permanent layer of plant residues. Under such conditions, soil compaction is reduced, soil structure improved, water infiltration enhanced, soil organic content increased and microbial activity stimulated. However, continuous soil cover, especially associated with permanent growth of plants, might also enhance plant-parasitic nematode densities due to permanent food supply. The effect of minimum tillage on nematode dynamics was studied within the EU-funded project “Optimizing subsidiary crop applications in rotations”. The rotation consisted of clover-grass, winter wheat, cover crop, and potato. The following treatments were studied: Plough versus minimum tillage, white clover versus subterranean clover as undersown crops in winter wheat, vetch versus a 1:4 mix of fodder radish and black oats as cover crop following winter wheat, and with and without 5t DM ha-1 compost application. Initially, the field was infested with Helicotylenchus, Meloidogyne, Paratylenchus, Pratylenchus and Tylenchorhynchus. Pratylenchus and Helicotylenchus increased under wheat and Meloidogyne was supported by white clover and subterranean clover as undersown crops. Population densities of all nematode taxa declined during the following catch crop and potato. There was no difference in nematode population dynamics between plough versus minimum tillage, nor between compost versus no compost. Results will be discussed considering the recent literature
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
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