| 1. |
- Alsanius, Beatrix, et al.
(författare)
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Internalization of Escherichia coli O157:H7 gfp+ in rocket and Swiss chard baby leaves as affected by abiotic and biotic damage
- 2017
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Ingår i: Letters in Applied Microbiology. - : Oxford University Press (OUP). - 0266-8254 .- 1472-765X. ; 65, s. 35-41
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Tidskriftsartikel (refereegranskat)abstract
- Internalization of human pathogens in edible parts of vegetables eaten raw is a major concern, since once internalized they are protected from sanitizing treatments. In this study, we examined the invasion of gfp-labelled Escherichia coli O157:H7 into intact and biotically (infection with Xanthomonas campestris/Pseudomonas syringae) and abiotically (grating with silicon carbide) damaged leaves of wild rocket (Diplotaxis tenuifolia) and Swiss chard (Beta vulgaris subsp. cicla) using laser scanning confocal microscopy. Bacterial cells were found in internal locations of the tissue, irrespective of tissue health status. Contaminated leaf sections of biotically and abiotically damaged wild rocket leaves showed higher susceptibility to microbial invasion, while the pathogen was internalized in greater numbers into intact Swiss chard leaf sections when abiotically, but not biotically, damaged. The greatest differences were observed between the plant species; after surface sanitization, E.coli O157:H7 was still detected in wild rocket leaves, but not in Swiss chard leaves.Significance and Impact of the StudyContamination of leafy vegetables with Escherichia coli O157:H7 is a growing problem, as reported outbreaks are increasing. However, establishment of this human pathogen in the phyllosphere is not completely understood. Using laser scanning confocal microscopy, we demonstrated that E.coli O157:H7gfp+ can invade plant tissue of Swiss chard and wild rocket leaves and that the bacterium is more sensitive to surface sanitization of Swiss chard leaves. Damage to leaf tissue promoted leaf invasion, but the nature of the damage (abiotic or biotic) and plant species had an impact.
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| 2. |
- Andersson, Martin N, et al.
(författare)
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What Reaches the Antenna? How to Calibrate Odor Flux and Ligand-Receptor Affinities
- 2012
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Ingår i: Chemical Senses. - : Oxford University Press (OUP). - 1464-3553 .- 0379-864X. ; 37:5, s. 403-420
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Tidskriftsartikel (refereegranskat)abstract
- Physiological studies on olfaction frequently ignore the airborne quantities of stimuli reaching the sensory organ. We used a gas chromatography-calibrated photoionization detector to estimate quantities released from standard Pasteur pipette stimulus cartridges during repeated puffing of 27 compounds and verified how lack of quantification could obscure olfactory sensory neuron (OSN) affinities. Chemical structure of the stimulus, solvent, dose, storage condition, puff interval, and puff number all influenced airborne quantities. A model including boiling point and lipophilicity, but excluding vapor pressure, predicted airborne quantities from stimuli in paraffin oil on filter paper. We recorded OSN responses of Drosophila melanogaster, Ips typographus, and Culex quinquefasciatus, to known quantities of airborne stimuli. These demonstrate that inferred OSN tuning width, ligand affinity, and classification can be confounded and require stimulus quantification. Additionally, proper dose-response analysis shows that Drosophila AB3A OSNs are not promiscuous, but highly specific for ethyl hexanoate, with other earlier proposed ligands 10- to 10 000-fold less potent. Finally, we reanalyzed published Drosophila OSN data (DoOR) and demonstrate substantial shifts in affinities after compensation for quantity and puff number. We conclude that consistent experimental protocols are necessary for correct OSN classification and present some simple rules that make calibration, even retroactively, readily possible.
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| 3. |
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| 4. |
- Bella David, Aneth, et al.
(författare)
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A comparative study on the impact of five Desmodium species on soil microbiome reveals enrichment of selected bacterial and fungal taxa
- 2023
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Introduction Several Desmodium spp. are used as intercrops in push-pull pest management systems to repel insect herbivores. In addition, Desmodium suppresses the parasitic weed Striga, and diversifies the soil microbiome with negative impacts on fungi. We investigated the impact of a 2-year cropping of five Desmodium species on soil microbiome populations.Methodology Total DNA was obtained from root zone soil samples collected from a two-years-old common garden experiment with replicated plots of five Desmodium spp. at the international centre for insect physiology and ecology (ICIPE), Mbita, Kenya. Subsequently, 16S and ITS DNA sequencing were performed and the data was analysed by using QIIME2 and Calypso.Results Our findings show significant differences in composition and abundance of specific microbial taxa among the Desmodium plots and the bulk soil, with a stronger shift observed for fungal community profiles than bacteria. There was, however, no significant difference in overall diversity, richness and evenness of microbial communities among the Desmodium plots and the bulk soil. Similarly, beta diversity analysis did not reveal a significant association of variation to specific Desmodium spp. plots.Discussion and conclusion This is the first study to compare impact and association of whole soil microbiomes to different Desmodium species. Whereas long-term Desmodium cropping clearly shifts whole microbiome communities, no significant difference in overall diversity and richness of microbial populations was observed among the studied plots. However, there was a divergence of individual taxa reflected on their increased abundance in association to specific Desmodium spp., pointing towards potential impact on ecosystem services. These findings indicate that significant shifts in whole microbial populations due to Desmodium spp. and thus potentially provision of associated ecosystem services require longer cultivation periods to solidify. Future studies should focus on techniques that monitor real-time changes in microbial populations such as RNA-seq to ascertain live and dead microbes, and thus infer ecological services.
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| 5. |
- Cunningham, Paul J., et al.
(författare)
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Do Fruit Ripening Volatiles Enable Resource Specialism in Polyphagous Fruit Flies?
- 2016
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Ingår i: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 42:9, s. 931-940
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Tidskriftsartikel (refereegranskat)abstract
- Frugivorous tephritid fruit flies have lineages with high levels of host generalism. These insects use olfaction to locate fruits, but how they are able to recognize the odors of so many different host species is poorly understood. We used a series of behavioral experiments to investigate the role of fruit ripening volatiles as host cues in the Queensland fruit fly, Bactrocera tryoni (Froggatt), a polyphagous pest in Australia. Odors of mature guava (Psidium guajava) attracted female and male flies more strongly than three other ripening stages and guava pulp. We analyzed volatiles from guava odor and selected eleven compounds, all of which elicited an electrophysiological response in the antenna of female flies. Three of these, ethyl acetate, ethyl butyrate, and ethyl propionate, were released at the highest rates from the most attractive ripening stage. In behavioral trials, these three esters were not attractive individually, whereas a combination was necessary and sufficient in attracting female flies. The three-component blend was as attractive as the entire 11-component blend, which without these key volatiles was not attractive. Moreover, injecting low ranking hosts (squash and cucumber) with the three volatiles increased attraction in ovipositing female flies. These fruit flies are classed as generalists, but like many polyphagous insects they could be regarded as resource specialists, preferring specific plant reproductive stages with predictable odor cues. Exploring olfaction from this perspective could improve our understanding of host choice in polyphagous insects, and the selection of volatiles to be used as attractants in insect pest management.
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| 6. |
- David Mwakilili, Aneth, et al.
(författare)
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Long-term maize-Desmodium intercropping shifts structure and composition of soil microbiome with stronger impact on fungal communities
- 2021
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036.
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Tidskriftsartikel (refereegranskat)abstract
- Purpose Push-pull is an intercropping technology that is rapidly spreading among smallholder farmers in Sub-Saharan Africa. The technology intercrops cereals with Desmodium to fight off stem borers, eliminate parasitic weeds, and improve soil fertility and yields of cereals. The above-ground components of push-pull cropping have been well investigated. However, the impact of the technology on the soil microbiome and the subsequent role of the microbiome on diverse ecosystem benefits are unknown. Here we describe the soil microbiome associated with maize-Desmodium intercropping in push-pull farming in comparison to long-term maize monoculture. Methods Soil samples were collected from long-term maize-Desmodium intercropping and maize monoculture plots at the international centre for insect physiology and ecology (ICIPE), Mbita, Kenya. Total DNA was extracted before16S rDNA and ITS sequencing and subsequent analysis on QIIME2 and R. Results Maize-Desmodium intercropping caused a strong divergence in the fungal microbiome, which was more diverse and species rich than monoculture plots. Fungal groups enriched in intercropping plots are linked to important ecosystem services, belonging to functional groups such as mycorrhiza, endophytes, saprophytes, decomposers and bioprotective fungi. Fewer fungal genera were enriched in monoculture plots, some of which were associated with plant pathogenesis and opportunistic infection in humans. In contrast, the impact of intercropping on soil bacterial communities was weak with few differences between intercropping and monoculture. Conclusion Maize-Desmodium intercropping diversifies fungal microbiomes and favors taxa associated with important ecosystem services including plant health, productivity and food safety.
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| 7. |
- Dejene Biasazin, Tibebe, et al.
(författare)
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Detection of Volatile Constituents from Food Lures by Tephritid Fruit Flies
- 2018
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Ingår i: Insects. - : MDPI AG. - 2075-4450. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Tephritid fruit flies require protein for sexual and gonotrophic development. Food-based lures are therefore widely used in strategies to detect and control fruit flies in the Tephritidae family. However, these baits are attractive to a broad range of insect species. We therefore sought to identify volatiles detected by the fly antennae, with the goal to compose lures that more specifically target tephritids. Using gas chromatography-coupled electroantennographic detection (GC-EAD) we screened for antennal responses of four important tephritid species to volatile compounds from five commercially available protein-based baits. Antennal active compounds were reconstituted in synthetic blends for each species and used in behavioral assays. These species-based blends were attractive in olfactometer experiments, as was a blend composed of all antennally active compounds from all the four species we observed (tested only in Bactrocera dorsalis, Hendel). Pilot field tests indicate that the blends need to be further evaluated and optimized under field conditions.
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| 8. |
- Dejene Biasazin, Tibebe, et al.
(författare)
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Differential responses of Bactrocera dorsalis and its parasitoids to headspaces of different varieties of tree-attached mango fruits and the associated chemical profiles
- 2022
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Bactrocera dorsalis (Hendel) is a major pest of fruits and vegetables worldwide with documented losses of up to 100%. Various management techniques including the use of parasitoids, such as Fopius arisanus (Sonan) and Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) within the context of the Integrated Pest Management (IPM) approach have been deployed for its control. The effectiveness of parasitoids is well understood, but knowledge of the semiochemicals that mediate their behavior, as well as that of the host fruit fly to tree-attached mangoes, is lacking. Here, we first compared the attractiveness of the above-mentioned fruit fly and its parasitoids to volatiles of different treatments (non-infested physiologically mature unripe and ripe mangoes, mangoes newly exposed to ovipositing B. dorsalis, and mangoes on day 7 and day 9 post-oviposition) of tree-attached Kent, Apple, and Haden mango varieties relative to control (clean air). The fruit fly was significantly more attracted to the mango volatiles (up to 93% of responsive insects) compared to the control (clean air). Fopius arisanus was significantly more attracted to mangoes with ovipositing fruit flies (68-76%) while D. longicaudata was significantly more attracted to day 9 post-oviposited mangoes (64-72%) compared to the control. Secondly, we elucidated the headspace volatile profiles of the non-infested and infested tree-attached mangoes using gas chromatography linked to mass spectrometry (GC-MS). The volatiles revealed various types of organic compounds with qualitative and quantitative differences. The majority of the compounds were esters making 33.8% of the total number, followed by sesquiterpenes-16.4%, and monoterpenes-15.4% among others. Most compounds had higher release rates in headspace volatiles of fruit fly-infested mangoes. Lastly, we harvested the infested mangoes and incubated them for puparia recovery. The number of puparia recovered varied according to the mango variety with Apple mango registering 81.7% of the total, while none was recovered from Kent. These results represent the first report of the changes in the headspace components of non-infested and infested tree-attached mangoes and the associated differential responses of the mentioned insects. A follow-up study can reveal whether there is a convergence in olfactomes which is significant when developing baits that selectively attract the fruit fly and not its natural enemies and fill the knowledge gap from an evolutionary ecological perspective.
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| 9. |
- Dejene Biasazin, Tibebe, et al.
(författare)
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Dispersal and competitive release affect the management of native and invasive tephritid fruit flies in large and smallholder farms in Ethiopia
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- African horticulture is seriously affected by fruit flies, both native and invasive. Novel sustainable control methods need testing against the backdrop of smallholder-dominated farming of Africa. We evaluated the potential of male-specific attractants (parapheromones) laced with insecticide to suppress the alien invasive Bactrocera dorsalis and native Ceratitis capitata. In large-scale guava, methyl-eugenol (ME)-bait stations combined with toxic protein baits suppressed B. dorsalis within 8 months but resulted in a resurgence of the displaced Ceratitis capitata. In smallholder farms, intervention using SPLAT-ME laced with spinosad was surprisingly unsuccessful. Subsequent mark-release-recapture experiments showed high dispersal rates of flies, covering many times a typical farm size, leading to a continuous influx of flies from surrounding areas. Several other factors important for intervention were evaluated. SPLAT-MAT-ME dollops remained attractive for over two weeks, although gradually becoming less attractive than fresh baits. Further, competitive displacement was observed: C. capitata selectively emerged from fruits in which B. dorsalis infestation was low. Finally, we evaluated whether ME could be combined with C. capitata male attractants [trimedlure (TML) and terpinyl acetate (TA)] without affecting attraction. Combining male lures did not affect catches directly, although at very high populations of B. dorsalis attracted to ME interfered with C. capitata trap entry. Although ME-based methods can effectively suppress B. dorsalis, they were not effective at single smallholder scale due to the high dispersive propensity of tephritids. Further, competitive release implies the need for a combination of lures and methods. These observations are important for developing control schemes tailored for African smallholder settings.
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| 10. |
- Dejene Biasazin, Tibebe, et al.
(författare)
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Identification of Host Blends that Attract the African Invasive Fruit Fly, Bactrocera invadens
- 2014
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Ingår i: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 40, s. 966-976
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Tidskriftsartikel (refereegranskat)abstract
- Bactrocera invadens, an invasive fruit fly species in the Afro-tropical region belonging to the Bactrocera dorsalis complex, causes considerable damage to fruit production and productivity. We sought to find attractants from hosts of B. invadens that could serve as baits in traps for monitoring and management of this pest. The attractiveness of volatiles from four different fruit species (mango, guava, banana and orange) at two stages of ripeness (ripe or unripe) was tested in an olfactometer assay. All fruits were attractive against a clean air control. Using hexane extracts of volatile collections of fruits, we demonstrated that male flies preferred the volatiles of ripe guava and orange over unripe fruit extracts. There was a slight difference in preference between females and males; females preferred orange to guava and mango, whereas males preferred mango and guava to orange. Gas chromatography/electroantennographic detection (GC/EAD) and GC/mass spectrometry (GC/MS) were used to identify compounds to which B. invadens antennae were sensitive. GC/EAD recordings from distal and medio-central parts of the fly antenna showed responses to a number of compounds from each fruit species, with esters dominating the responses. Synthetic blends were made for each fruit species using the shared antennally active compounds in ratios found in the extracts. In the olfactometer, B. invadens was most attracted to the banana and orange blends, followed by the mango and guava blends. The synthetic banana blend was as attractive as the volatile collection of banana, although both were less attractive than the fruit. The results demonstrate that composing attractive blends from GC/EAD-active constituents shared by host fruits can be effective for formulating attractive synthetic host mimics for generalist fruit fly species, such as B. invadens.
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