Glass-fibre Discs Research Articles

Antibacterial activity of biosynthesized silver nanoparticles (AgNps) against Pectobacterium carotovorum.

In a bioprospecting study of paramo soils cultivated with potato (Solanum tuberosum), 50 fungal isolates were obtained and evaluated for their nitrate reductase (NR) activity, given the role played by this enzyme in the biosynthesis of silver nanoparticles (AgNps). Five isolates strain with high NR activity belonging to Penicillium simplicissimum, Aspergillus niger, and Fusarium oxysporum species were selected, verifying the presence of the NR enzyme in their enzymatic extract. Later, these strains showed the ability to biosynthesize AgNps with distorted spherical shapes and sizes ranging from 15 to 45nm. Subsequently, an antibiosis test was carried out by the agar diffusion method using glass fiber disks against the phytopathogenic agent Pectobacterium carotovorum, finding halos of inhibition of bacterial growth up to 15.3mm using a 100ppm solution of the AgNps obtained from F. oxysporum. These results contribute to generating the basis of a new alternative for the control of this phytopathogenic agent of potato, challenging to manage by traditional methods and of relevance at the post-harvest level.

Metabolomic differences between invasive alien plants from native and invaded habitats

Globalization facilitated the spread of invasive alien species (IAS), undermining the stability of the world’s ecosystems. We investigated the metabolomic profiles of three IAS species: Chromolaena odorata (Asteraceae) Datura stramonium (Solanaceae), and Xanthium strumarium (Asteraceae), comparing metabolites of individual plants in their native habitats (USA), to their invasive counterparts growing in and around Kruger National Park (South Africa, ZA). Metabolomic samples were collected using RApid Metabolome Extraction and Storage (RAMES) technology, which immobilizes phytochemicals on glass fiber disks, reducing compound degradation, allowing long-term, storage and simplifying biochemical analysis. Metabolomic differences were analyzed using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) of samples eluted from RAMES disks. Partial Least Squares-Discriminant Analysis (PLS-DA) of metabolomes of individual plants allowed statistical separation of species, native and invasive populations of each species, and some populations on the same continent. Invasive populations of all species were more phytochemically diverse than their native counterparts, and their metabolomic profiles were statistically distinguishable from their native relatives. These data may elucidate the mechanisms of successful invasion and rapid adaptive evolution of IAS. Moreover, RAMES technology combined with PLS-DA statistical analysis may allow taxonomic identification of species and, possibly, populations within each species.

Bioactivity of Common Pesticidal Plants on Fall Armyworm Larvae (Spodoptera frugiperda).

The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is a recent invasive pest species that has successfully established across sub-Saharan Africa where it continues to disrupt agriculture, particularly smallholder cereal production. Management of FAW in its native range in the Americas has led to the development of resistance to many commercial pesticides before its arrival in Africa. Pesticide use may therefore be ineffective for FAW control in Africa, so new and more sustainable approaches to pest management are required that can help reduce the impact of this exotic pest. Pesticidal plants provide an effective and established approach to pest management in African smallholder farming and recent research has shown that their use can be cost-beneficial and sustainable. In order to optimize the use of botanical extracts for FAW control, we initially screened ten commonly used plant species. In laboratory trials, contact toxicity and feeding bioassays showed differential effects. Some plant species had little to no effect when compared to untreated controls; thus, only the five most promising plant species were selected for more detailed study. In contact toxicity tests, the highest larval mortality was obtained from Nicotiana tabacum (66%) and Lippia javanica (66%). Similarly, in a feeding bioassay L. javanica (62%) and N. tabacum (60%) exhibited high larval mortality at the highest concentration evaluated (10% w/v). Feeding deterrence was evaluated using glass-fibre discs treated with plant extracts, which showed that Cymbopogon citratus (36%) and Azadirachta indica (20%) were the most potent feeding deterrents among the pesticidal plants evaluated. In a screenhouse experiment where living maize plants infested with fall armyworm larvae were treated with plant extracts, N. tabacum and L. javanica were the most potent species at reducing foliar damage compared to the untreated control whilst the synthetic pesticide chlorpyrifos was the most effective in reducing fall armyworm foliar damage. Further field trial evaluation is recommended, particularly involving smallholder maize fields to assess effectiveness across a range of contexts.

Optimum reductants ratio for CO<sub>2</sub> reduction by overlapped Cu/TiO<sub>2</sub>

Cu-doped TiO2 (Cu/TiO2) film photocatalyst was prepared by combination of sol-gel and dip-coating process, and pulse arc plasma method. The effect of Cu/TiO2 photocatalyst on CO2 reduction performance with reductants of H2O and H2 was investigated. In addition, this study investigated overlapping two Cu/TiO2 coated on netlike glass fiber discs in order to utilize the light effectively as well as increase the amount of photocatalyst used for CO2 reduction. The characterization of prepared Cu/TiO2 film coated on netlike glass fiber was analyzed by SEM, EPMA, TEM and EELS. Furthermore, the CO2 reduction performance of Cu/TiO2 film was tested under illumination of Xe lamp with or without ultraviolet (UV) light, respectively. As a result, the best CO2 reduction performance has been achieved under the condition of CO2/H2/H2O = 1:0.5:0.5 with UV light illumination as well as without UV light illumination. Under the illumination condition with UV light, the highest concentration of CO for Cu/TiO2 overlapped is 1.4 times as large as that for single Cu/TiO2, while the highest concentration of CH4 for Cu/TiO2 overlapped is 1.7 times as that for single Cu/TiO2. Under the illumination condition without UV light, the highest molar quality of CO per weight of photocatalyst for Cu/TiO2 overlapped is 1.1 times as that for single Cu/TiO2. The theoretical molar ratio of CO2/H2O or CO2/H2 to produce CO is 1:1, while the theoretical molar ratio of CO2/H2O or CO2/H2 to produce CH4 is 1:4. Since the molar ratio of CO2/H2/H2O = 1:0.5:0.5 can be regarded as the molar ratio of CO2/total reductants = 1:1, it is believed that the results of this study follow the reaction schemes of CO2/H2O and CO2/H2.

Rapid, field-deployable method for collecting and preserving plant metabolome for biochemical and functional characterization.

Study of plant metabolome is a growing field of science that catalogs vast biochemical and functional diversity of phytochemicals. However, collecting and storing samples of plant metabolome, sharing these samples across the scientific community and making them compatible with bioactivity assays presents significant challenges to the advancement of metabolome research. We have developed a RApid Metabolome Extraction and Storage (RAMES) technology that allows efficient, highly compact, field-deployable collection and storage of libraries of plant metabolome. RAMES technology combines rapid extraction with immobilization of extracts on glass microfiber filter discs. Two grams of plant tissue extracted in ethanol, using a specially adapted Dremel® rotary tool, produces 25–35 replicas of 10 mm glass fiber discs impregnated with phytochemicals. These discs can be either eluted with solvents (such as 70% ethanol) to study the metabolomic profiles or used directly in a variety of functional assays. We have developed simple, non-sterile, anti-fungal, anti-bacterial, and anti-oxidant assays formatted for 24-multiwell plates directly compatible with RAMES discs placed inside the wells. Using these methods we confirmed activity in 30 out of 32 randomly selected anti-microbial medicinal plants and spices. Seven species scored the highest activity (total kill) in the anti-bacterial (bacteria from human saliva) and two anti-fungal screens (Fusarium spp. and Saccharomyces cerevisiae), providing functional validation of RAMES technology. RAMES libraries showed limited degradation of compounds after 12 months of storage at -20°C, while others remained stable. Fifty-eight percent of structures characterized in the extracts loaded onto RAMES discs could be eluted from the discs without significant losses. Miniaturized RAMES technology, as described and validated in this manuscript offers a labor, cost, and time-effective alternative to conventional collection of phytochemicals. RAMES technology enables creation of comprehensive metabolomic libraries from various ecosystems and geographical regions in a format compatible with further biochemical and functional studies.

Immunochromatographic thread-based test platform for diagnosis of infectious diseases

Patterning is an important step in fabrication of multiplexed microfluidic devices. Various approaches including cutting, photolithography, wax-printing, plotting and etching have been developed and tested. Recently, using threads has emerged as a convenient and low-cost approach for fabrication of microfluidic devices. We explored the application of threads in combination with nitrocellulose membrane to fabricate multi-channel immunochromatographic diagnostic devices. Microfluidic channels were made using hydrophilic threads and nitrocellulose membrane strips. Household sewing needle was used to weave hydrophilic thread into desired patterns through a double-sided mounting tape. Glass fibre discs were used as conjugate pads while nitrocellulose membrane was used for immobilisation of capture antibodies. Patterned threads were linked to nitrocellulose membrane strips by overlapping so that reagents flowing through threads were eventually transferred to the membrane. The design was tested using IgG, H. pylori and Hepatitis B surface antigen. Continuous flow was observed from hydrophilic threads to the nitrocellulose membrane, and a positive signal was visualised on the membrane within 5 min of sample application. The observed limit of detection ranged between 30 and 300 ng/ml for H. pylori and Hepatitis B, respectively. Using thread and tape offers a promising alternative for patterning of simple, low-cost multiplexed microfluidic diagnostic devices with potential point-of-care applications in resource-limited settings.

Mechanical properties and superficial characterization of a milled CAD-CAM glass fiber post.

Computer-aided design and computer-aided manufacturing (CAD-CAM) technology may be used to produce custom intraradicular posts, but studies are lacking. The purpose of this in vitro study was to evaluate the flexural properties (strength and modulus), failure mode, superficial morphology, and roughness of two CAD-CAM glass fiber posts (milled at different angulations) compared with a commercially available prefabricated glass fiber post. Three groups were tested (n = 10): PF (control group)- prefabricated glass fiber post; C-Cd-diagonally milled post; and C-Cv-vertically milled post. A 3-dimensional virtual image was obtained from a prefabricated post, which guided the posterior milling of posts from a glass fiber disk (Trilor Blanks; Bioloren). Surface roughness and morphology were evaluated using confocal laser microscopy. Flexural strength and modulus were evaluated with the 3-point bend test. Data were submitted to one-way analysis of variance followed by the Student-Newman-Keuls post hoc test (α = 0.05). The fractured surfaces were evaluated with scanning electron microscopy. The superficial roughness was highest for PF and similar for the experimental groups. Morphological analysis shows different sizes and directions of the glass fibers along the post. The flexural strength was highest for PF (900.1 ± 30.4 > C-Cd - 357.2 ± 30.7 > C-Cv 101.8 ± 4.3 MPa) as was the flexural modulus (PF 19.3 ± 2.0 GPa > C-Cv 10.1 ± 1.9 GPa > C-Cd 7.8 ± 1.3 GPa). A CAD-CAM milled post seems a promising development, but processing requires optimizing, as the prefabricated post still shows better mechanical properties and superficial characteristics.

One dimensional zinc oxide nanostructures assisted paper-based blood-plasma separation

Low-cost, paper-based platforms are gaining increasing relevance in modern diagnostics and biosensing. Most diagnostic systems using blood samples require blood-plasma separation to reduce complexity and achieve better results. Blood plasma separation is often carried-out by using various membrane based filters. This paper presents a new method for capturing red blood cells on Whatman filter paper with no. 1, 2, 5 and glass fiber discs. All four paper types were subjected to modification with hydrothermally grown zinc oxide nanorods. Growth and morphologies of zinc oxide nanorods were confirmed by SEM, XRD and XPS studies. The blood plasma separation experiments were done by cutting the papers into identical strips with dimension of 5 × 20 mm2. 3 μL of blood was mixed with equal volume of antibody solution and pipetted on each strip. The colored antibody solution was used to track the path of antibody, eventually the separated plasma. The dried strips were scanned and the difference in the distance travelled by colored solution of antibodies was measured. From the results, it is clear that all four paper strips covered with nanorods have shown more distance travelled and better separation than their control samples.

Microwave-induced combustion: Thermal and morphological aspects for understanding the mechanism of ignition process for analytical applications

In the present work, for the first time a systematic study was performed using an infrared camera and scanning electron microscopy (SEM) coupled to energy dispersive X-ray spectrometry (EDS) to evaluate the mechanisms involved in microwave-induced combustion method, which has been extensively used for sample preparation. Cellulose and glass fiber discs, wetted with the igniter solution (6molL−1 NH4NO3), were evaluated under microwave field in a monomode system. The temperature of the discs surface was recorded during microwave irradiation and the effect of NH4NO3 concentration and irradiation time on cellulose oxidation was evaluated. The morphology of the discs surface was characterized by SEM before and after irradiation in an inert atmosphere. According to the results, the surface temperature of the discs increased near to 100°C and remained in this temperature for few seconds while water evaporate. After that, temperature increased over 200°C due to the thermal decomposition of NH4NO3 salt, releasing a large amount of energy that accelerates cellulose oxidation. The higher the igniter concentration, the shorter was the microwave irradiation time for cellulose oxidation. The SEM images revealed that cellulose disc was more porous after microwave irradiation, enhancing oxygen diffusion within the paper and making easier its ignition. The EDS spectrum of cellulose and glass fiber discs showed that signal intensity for nitrogen decreased after microwave irradiation, showing that NH4NO3 was consumed during this process. Therefore, it was demonstrated that the ignition process is the result of synergic interaction of NH4NO3 thermal decomposition and organic matter oxidation (cellulose) releasing heat and feeding the chain reaction.

An acid precipitation technique: A strip assay for the large-scale DNA polymerase activity screening

A new format of a very rapid, low-cost and high-productive analysis based on the acid precipitation of radiolabeled DNA was developed. By contrast to the conventional processing of a large number of GF/C discs, the method employs one GF/C strip containing samples on individual teeth. The strip assay was validated by comparison with the glass fiber disk technique; the efficiency was demonstrated by screening E. coli superproducers and fractions obtained at the steps of Bst DNA polymerase, Large Fragment purification by the protocol we developed. The principle proposed allows simultaneous assaying many samples for the activity of different polymerases.

Impact of Overlapping Fe/TiO2Prepared by Sol-Gel and Dip-Coating Process on CO2Reduction

Fe-doped TiO2(Fe/TiO2) film photocatalyst was prepared by sol-gel and dip-coating process to extend its photoresponsivity to the visible spectrum. To promote the CO2reduction performance with the photocatalyst, some types of base materials used for coating Fe/TiO2, which were netlike glass fiber and Cu disc, were investigated. The characterization of prepared Fe/TiO2film coated on netlike glass fiber and Cu disc was analyzed by SEM and EPMA. In addition, the CO2reduction performance of Fe/TiO2film coated on netlike glass disc, Cu disc, and their overlap was tested under a Xe lamp with or without ultraviolet (UV) light, respectively. The results show that the concentration of produced CO increases by Fe doping irrespective of base material used under the illumination condition with UV light as well as that without UV light. Since the electron transfer between two overlapped photocatalysts is promoted, the peak concentration of CO for the Fe/TiO2double overlapping is approximately 1.5 times as large as the Fe/TiO2single overlapping under the illumination condition with UV light, while the promotion ratio is approximately 1.1 times under that without UV light.

Taste discriminating capability to different bitter compounds by the larval styloconic sensilla in the insect herbivore Papilio hospiton (Géné)

Herbivorous animals may benefit from the capability to discriminate the taste of bitter compounds since plants produce noxious compounds, some of which toxic, while others are only unpalatable. Our goal was to investigate the contribution of the peripheral taste system in the discrimination of different bitter compounds by an herbivorous insect using the larvae of Papilio hospiton Géné as the experimental model, showing a narrow choice range of host plants. The spike activity from the lateral and medial styloconic sensilla, housing two and one bitter-sensitive gustatory receptor neurons (GRNs), respectively, was recorded following stimulation with nicotine, caffeine, salicin and quercitrin and the time course of the discharges was analyzed. Nicotine and caffeine activated all three bitter-sensitive GRNs, while salicin and quercitrin affected only two of them. In feeding behavior bioassays, intact larvae ate glass-fiber disks moistened with salicin and quercitrin, but rejected those with nicotine and caffeine, while lateral sensillum-ablated insects also ate the disks with the two latter compounds. The capability to discriminate bitter taste stimuli and the neural codes involved are discussed.

Measurement of photosynthesis using PAM technology in a purple sulfur bacterium Thermochromatium tepidum (Chromatiaceae).

We demonstrate that Blue-diode-based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) of purple sulfur bacteria (Thermochromatium tepidum, Chromatiaceae). Previous studies showed that PAM technology could be used to estimate photosynthesis in purple nonsulfur bacteria and so PAM technology can be used to estimate photosynthesis of both kinds of purple photosynthetic bacteria. The absorptance of Thermochromatium films on glass fiber disks was measured and used to calculate actual ETR. ETR vs Irradiance (P vs E) curves fitted the waiting-in-line model (ETR = (ETRmax × E/Eopt) × exp (1−E/Eopt)). Yield (Y) was only ≈ 0.3–0.4. Thermochromatium saturates at 325 ± 13.8 μmol photons m(−2) s(−1) or ≈15% sunlight and shows photoinhibition at high irradiances. A pond of Thermochromatium would exhibit classic surface inhibition. Photosynthesis is extremely low in the absence of an electron source: ETR increases in the presence of acetate (5 mol m(−3)) provided as an organic carbon source and also increases in the presence of sulfite (3 mol m(−3)) but not sulfide and is only marginally increased by the presence of Fe(2+). Nonphotochemical quenching does occur in Thermochromatium but at very low levels compared to oxygenic photo-organisms or Rhodopseudomonads.

Photosynthesis in an Encrusting Lichen (Dirinaria picta(Sw.) Schaer.ex Clem., Physiaceae) and its Symbiont,Trebouxiasp., Using Pulse Amplitude Modulation Fluorometry

Premise of research. The encrusting arboreal lichen Dirinaria picta (Sw.) Schaer.ex Clem. (Physiaceae) is commonly found growing on tree trunks in Thailand and globally in the tropics and subtropics. Trebouxia sp. is its chlorophyte symbiont. Pulse amplitude modulation (PAM) techniques have been used to measure photosynthesis of a tropical lichen as well as its cultured symbiont. PAM technology has not been used to full advantage in lichens.Methodology. Absorptance of the thalli and glass fiber disks impregnated with cultured Trebouxia was measured with a leaf absorptance meter. PAM fluorometers measure the light reactions of photo-organisms to estimate gross photosynthesis (Pg; mol O2 m−2 s−1) from the measured electron transport rate through PSII (4 electrons per O2), provided that the absorptance of the photo-organism is known. Photosynthesis-versus-irradiance curves were measured with a blue-diode PAM machine and fitted to the waiting-in-line function.Pivotal results. The absorptance of moist active l...

Photosynthetic Electron Transport in an Anoxygenic Photosynthetic Bacterium Afifella (Rhodopseudomonas) marina Measured Using PAM Fluorometry

Blue diode-based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) in a purple nonsulfur anoxygenic photobacterium, Afifella (Rhodopseudomonas) marina. Rhodopseudomonads have a reaction center light harvesting antenna complex containing an RC-2 type bacteriochlorophyll a protein (BChl a RC-2-LH1) which has a blue absorption peak and variable fluorescence similar to PSII. Absorptance of cells filtered onto glass fiber disks was measured using a blue-diode-based absorptance meter (Blue-RAT) so that absolute ETR could be calculated from PAM experiments. Maximum quantum yield (Y) was ≈0.6, decreasing exponentially as irradiance increased. ETR vs irradiance (P vs E) curves fitted the waiting-in-line model (ETR=(ETRmax ×E/Eopt )×exp(1-E/Eopt )). Maximum ETR (ETRmax ) was ≈1000-2000μmole(-) mg(-1) BChl ah(-1) . Fe(2+) , bisulfite and thiosulfate act as photosynthetic electron donors. Optimum irradiance was ≈100μmolm(-2) s(-1) PPFD even in Afifella grown in sunlight. Quantum efficiencies (α) were ≈0.3-0.4mole(-) molhλ(-1) ; or ≈11.8±2.9mole(-) molhλ(-1) m(2) μg(-1) BChl a). An underlying layer of Afifella in a constructed algal/photosynthetic bacterial mat has little effect on the measured ETR of the overlying oxyphotoautotroph (Chlorella).

Quantifying dynamic resource allocation illuminates foraging strategy in Phanerochaete velutina

Saprotrophic woodland fungi forage for mineral nutrients and woody resources by extension of a mycelial network across the forest floor. Different species explore at different rates and establish networks with qualitatively differing architecture. However, detailed understanding of fungal foraging behaviour has been hampered by the absence of tools to quantify resource allocation and growth accurately and non-invasively. To solve this problem, we have used photon-counting scintillation imaging (PCSI) to map and quantify nutrient allocation and localised growth simultaneously in heterogeneous resource environments. We show that colonies spontaneously shift to an asymmetric growth pattern, even in the absence of added resources, often with a distinct transition between the two growth phases. However, the extent of polarisation was much more pronounced and focussed in the presence of an additional cellulose resource. In this case, there was highly localised growth, often at the expense of growth elsewhere in the colony, and marked accumulation of 14C-AIB in the sector of the colony with the added resource. The magnitude of the response was greatest when resource was added around the time of the endogenous developmental transition. The focussed response required a metabolisable resource, as only limited changes were seen with glass fibre discs used to mimic the osmotic and thigmotropic stimuli upon resource addition. Overall the behaviour is consistent with an adaptive foraging strategy, both to exploit new resources and also to redirect subsequent foraging effort to this region, presumably with an expectation that the probability of finding additional resources is increased.

Fungal isolates involved in biodeterioration of book-paper and their effects on substrate selection by Liposcelis bostrychophila (Badonnel) (Psocoptera: Liposcelididae)

The effects of fungi on the distribution of groups of Liposcelis bostrychophila were investigated. Two strains of Ulocladium botrytis were obtained from biodeteriorated book-paper and Eurotium amstelodami was isolated from the food used to culture L. bostrychophila. Isolated fungi were cultured on either paper sterilised with ethanol (paper) or on a malt-agar medium (medium). One strain or species was presented to groups of L. bostrychophila on a glass-fibre disc, with a blank disc as the other choice, and the number of insects on each disc and those free in the Petri dish was recorded after 12 h. In general a lower proportion of insects selected when one of the choices was either a 10,000 ppm extract of extract of U. botrytis cultured on malt-agar or one of the more dilute extracts of U. botrytis cultured on either medium. In contrast, extracts of both strains of U. botrytis (paper, 10,000 ppm) and E. amstelodami (malt-agar medium; 10,000; 1000 and 100 ppm) did not affect the proportion of insects that selected. With the exception of an extract of one of the strains of U. botrytis (paper; 10,000 ppm) significantly more selecting insects were found on the blank disc. A second set of experiments, in which extracts were applied to both discs, showed that L. bostrychophila did differentiate between the same fungus grown on paper or malt-agar medium and also between extracts of U. botrytis and E. amstelodami. It would appear that fungi grown on malt-agar medium are more repellent than fungi grown on paper and that E. amstelodami is preferred to U. botrytis. However, the selection of a substrate by L. bostrychophila very much depends on the context in which it is provided, i.e. the other choice.

Analysis of inflammatory biomarkers from tissue biopsies by chip‐based immunoaffinity CE

To aid in the biochemical analysis of human skin biopsies, a semiautomatic chip-based CE system has been developed for measuring inflammatory biomarkers in microdissected areas of the biopsy. Following solubilization of the dissected tissue, the desired biomarkers were isolated by immunoaffinity capture using a panel of 12 antibodies, immobilized on a disposable glass fiber disk, within the extraction port of the chip. The captured analytes were labeled with a 635 nm light-emitting laser dye and electroeluted into the separation channel. Electrophoretic separation of all of the analytes was achieved in 2.2 min with quantification of each peak being performed by online LIF detection and integration of each peak area. Comparison of the results obtained from the chip-based system to those obtained using commercially available high-sensitivity immunoassays demonstrated that the chip-based assay provides a fast, accurate procedure for studying the concentrations of inflammatory biomarkers in complex biological materials. The degree of accuracy and precision achieved by the chip-based CE is comparable to conventional immunoassays and the system is capable of analyzing circa six samples per hour. With the ever-expanding array of antibodies that are commercially available, this chip-based system can be applied to a wide variety of different biomedical analyses.

The effects of alkaloids on the feeding behavior of gypsy moth larvae

The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), is a major defoliator of forest habitats in North America. These larvae feed on the foliage of hundreds of plants, but prefer leaves from deciduous hardwood trees such as sweetgum, maple, and oak. Plants contain a variety of phytochemicals, some of which are insect feeding deterrents. Deterrent compounds influence the food selection of many phytophagous insects including gypsy moth larvae. Deterrent compounds, such as alkaloids, are generally unfavored and typically avoided by these larvae. We tested the effects of eight alkaloids using two-choice feeding bioassays. Each alkaloid was applied to glass fiber disks and red oak leaf disks. All eight alkaloids tested on glass fiber disks were deterrent to varying degrees. When these alkaloids were applied to leaf disks, however, only seven were still deterrent. Of these seven, five were less deterrent on leaf disks compared with glass fiber disks, indicating that their potency was dramatically reduced when they were applied to leaf disks. The reduction in deterrency may be attributed to the phagostimulatory effect of red oak leaves in suppressing the negative deterrent effect of these alkaloids, suggesting that individual alkaloids may confer context-dependent deterrent effects in plants in which they occur. We also tested the effects of these eight alkaloids at six concentrations spanning four logarithmetic steps to determine deterrent threshold effects. This study provides novel insights into the feeding behavioral responses of gypsy moth larvae to selected deterrent alkaloids. Our results may be potentially useful in designing crop protection strategies from insect pests and will help to improve our understanding of insect feeding behavior. Supported by NIH grant 1 R15 DC007609-01 to V.S. and Bridges NIH grant 5R25GM058264-03.

Feeding responses to selected alkaloids by gypsy moth larvae, Lymantria dispar (L.)

Deterrent compounds are important in influencing the food selection of many phytophagous insects. Plants containing deterrents, such as alkaloids, are generally unfavored and typically avoided by many polyphagous lepidopteran species, including the gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae). We tested the deterrent effects of eight alkaloids using two-choice feeding bioassays. Each alkaloid was applied at biologically relevant concentrations to glass fiber disks and leaf disks from red oak trees (Quercus rubra) (L.), a plant species highly favored by these larvae. All eight alkaloids tested on glass fiber disks were deterrent to varying degrees. When these alkaloids were applied to leaf disks, only seven were still deterrent. Of these seven, five were less deterrent on leaf disks compared with glass fiber disks, indicating that their potency was dramatically reduced when they were applied to leaf disks. The reduction in deterrency may be attributed to the phagostimulatory effect of red oak leaves in suppressing the negative deterrent effect of these alkaloids, suggesting that individual alkaloids may confer context-dependent deterrent effects in plants in which they occur. This study provides novel insights into the feeding behavioral responses of insect larvae, such as L. dispar, to selected deterrent alkaloids when applied to natural vs artificial substrates and has the potential to suggest deterrent alkaloids as possible candidates for agricultural use.