ORCID Profile
0000-0001-6374-6684
Current Organisations
Fujita Health University
,
Western Sydney University
,
University of Delaware
,
Agroscope Standort Changins
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Publisher: Springer Science and Business Media LLC
Date: 26-02-2021
DOI: 10.1007/S10340-021-01349-4
Abstract: Entomopathogenic nematodes (EPN) have great potential as biological control agents against root-feeding insects. They have a rapid and long-lasting mode of action, minimal adverse effects on the environment and can be readily mass-produced. However, they have a relatively short shelf-life and are susceptible to desiccation and UV light. These shortcomings may be overcome by encapsulating EPN in Ca 2+ -alginate hydrogels, which have been shown to provide a humid and UV protective shelter. Yet, current Ca 2+ -alginate formulations do not keep EPN vigorous and infectious for a prolonged period of time and do not allow for their controlled release upon application. Here, we introduce solid Ca 2+ -alginate beads which we supplemented with glycerol to better retain the EPN during storage and to ensure a steady release when applied in soil. Glycerol-induced metabolic arrest in EPN ( Heterorhabditis bacteriophora ) resulting in quiescence and total retainment of EPN when added to beads made with 0.5% sodium alginate and 2% CaCl 2 ·2H 2 O solutions. More than 4,000 EPN could be embedded in a single 4–5-mm diameter bead, and quiescence could be broken by adding water, after which the EPN readily emerged from the beads. In a field trial, the EPN beads were as effective in reducing root damage by the western corn rootworm (WCR, Diabrotica virgifera virgifera ) as EPN that were applied in water. Although further improvements are desirable, we conclude that Ca 2+ -alginate beads can provide an effective and practical way to apply EPN for the control of WCR larvae.
Publisher: Springer Science and Business Media LLC
Date: 18-05-2012
DOI: 10.1007/S10886-012-0131-9
Abstract: In most agro-ecosystems the organisms that feed on plant roots have an important impact on crop yield and can impose tremendous costs to farmers. Similar to aboveground pests, they rely on a broad range of chemical cues to locate their host plant. In their turn, plants have co-evolved a large arsenal of direct and indirect defense to face these attacks. For instance, insect herbivory induces the synthesis and release of specific volatile compounds in plants. These volatiles have been shown to be highly attractive to natural enemies of the herbivores, such as parasitoids, predators, or entomopathogenic nematodes. So far few of the key compounds mediating these so-called tritrophic interactions have been identified and only few genes and biochemical pathways responsible for the production of the emitted volatiles have been elucidated and described. Roots also exude chemicals that directly impact belowground herbivores by altering their behavior or development. Many of these compounds remain unknown, but the identification of, for instance, a key compound that triggers nematode egg hatching to some plant parasitic nematodes has great potential for application in crop protection. These advances in understanding the chemical emissions and their role in ecological signaling open novel ways to manipulate plant exudates in order to enhance their natural defense properties. The potential of this approach is discussed, and we identify several gaps in our knowledge and steps that need to be taken to arrive at ecologically sound strategies for belowground pest management.
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.JIP.2014.08.002
Abstract: As obligate parasites, entomopathogenic nematodes (EPN) rely on insect hosts to complete their development. In insect pest management, EPN infectiousness has varied a lot. A better understanding of their host-finding behavior in the rhizosphere is therefore crucial to enhance EPN potential in biological control. As previously demonstrated, roots can be used as a pathway to insect hosts by EPN, but this interaction and its impact on EPN foraging remain poorly documented. Three artificial model-roots with different degrees of complexity and connectivity were designed to investigate the impact of root architecture on foraging behavior of the EPN Heterorhabditis megidis. Insect baits were placed at the bottom of each model-root that was subsequently buried in moist sand. After injection of the EPN, the number of EPN-infected baits as well as the number of mature nematodes inside each in idual carcass was recorded. The influence of insect-induced root volatiles was also evaluated by spiking the baits with a synthetic version of a natural insect-induced root cue. The ecological relevance of the results was tested in soil with two maize genotypes each exhibiting broadly different root architectures. H. megidi performed better in presence of model-roots. Foraging performances of H. megidis declined with the increasing model-root complexity. Adding the synthetic root volatile dramatically changed this pattern and favored the EPN on the most complex model-roots. H. megidis also moved in the vicinity of maize roots to find the insect baits in soil, and natural root architecture also tended to shape H. megidis foraging behavior. This study adds to the scarce body of literature characterizing physical and chemical interactions between EPN and roots. The present data illustrate that root architecture not only modifies plant quality but also shapes upper trophic levels' ecology.
Publisher: Springer Science and Business Media LLC
Date: 04-2005
DOI: 10.1038/NATURE03451
Abstract: Plants under attack by arthropod herbivores often emit volatile compounds from their leaves that attract natural enemies of the herbivores. Here we report the first identification of an insect-induced belowground plant signal, (E)-beta-caryophyllene, which strongly attracts an entomopathogenic nematode. Maize roots release this sesquiterpene in response to feeding by larvae of the beetle Diabrotica virgifera virgifera, a maize pest that is currently invading Europe. Most North American maize lines do not release (E)-beta-caryophyllene, whereas European lines and the wild maize ancestor, teosinte, readily do so in response to D. v. virgifera attack. This difference was consistent with striking differences in the attractiveness of representative lines in the laboratory. Field experiments showed a fivefold higher nematode infection rate of D. v. virgifera larvae on a maize variety that produces the signal than on a variety that does not, whereas spiking the soil near the latter variety with authentic (E)-beta-caryophyllene decreased the emergence of adult D. v. virgifera to less than half. North American maize lines must have lost the signal during the breeding process. Development of new varieties that release the attractant in adequate amounts should help enhance the efficacy of nematodes as biological control agents against root pests like D. v. virgifera.
Publisher: Proceedings of the National Academy of Sciences
Date: 11-08-2009
Abstract: When attacked by herbivorous insects, plants emit volatile compounds that attract natural enemies of the insects. It has been proposed that these volatile signals can be manipulated to improve crop protection. Here, we demonstrate the full potential of this strategy by restoring the emission of a specific belowground signal emitted by insect-damaged maize roots. The western corn rootworm induces the roots of many maize varieties to emit ( E )-β-caryophyllene, which attracts entomopathogenic nematodes that infect and kill the voracious root pest. However, most North American maize varieties have lost the ability to emit ( E )-β-caryophyllene and may therefore receive little protection from the nematodes. To restore the signal, a nonemitting maize line was transformed with a ( E )-β-caryophyllene synthase gene from oregano, resulting in constitutive emissions of this sesquiterpene. In rootworm-infested field plots in which nematodes were released, the ( E )-β-caryophyllene-emitting plants suffered significantly less root damage and had 60% fewer adult beetles emerge than untransformed, nonemitting lines. This demonstration that plant volatile emissions can be manipulated to enhance the effectiveness of biological control agents opens the way for novel and ecologically sound strategies to fight a variety of insect pests.
Publisher: No publisher found
Date: 2009
Publisher: Oxford University Press (OUP)
Date: 02-2008
Abstract: The sesquiterpene (E)-β-caryophyllene is emitted by maize (Zea mays) leaves in response to attack by lepidopteran larvae like Spodoptera littoralis and released from roots after damage by larvae of the coleopteran Diabrotica virgifera virgifera. We identified a maize terpene synthase, Terpene Synthase 23 (TPS23), that produces (E)-β-caryophyllene from farnesyl diphosphate. The expression of TPS23 is controlled at the transcript level and induced independently by D. v. virgifera damage in roots and S. littoralis damage in leaves. We demonstrate that (E)-β-caryophyllene can attract natural enemies of both herbivores: entomopathogenic nematodes below ground and parasitic wasps, after an initial learning experience, above ground. The biochemical properties of TPS23 are similar to those of (E)-β-caryophyllene synthases from dicotyledons but are the result of repeated evolution. The sequence of TPS23 is maintained by positive selection in maize and its closest wild relatives, teosinte (Zea sp) species. The gene encoding TPS23 is active in teosinte species and European maize lines, but decreased transcription in most North American lines resulted in the loss of (E)-β-caryophyllene production. We argue that the (E)-β-caryophyllene defense signal was lost during breeding of the North American lines and that its restoration might help to increase the resistance of these lines against agronomically important pests.
Publisher: MDPI AG
Date: 30-08-2021
Abstract: The fall armyworm (FAW), Spodoptera frugiperda (Smith), is a polyphagous pest whose larval feeding threatens several economically important crops worldwide with especially severe damage to corn (Zea mays L.). Field-derived resistance to several conventional pesticides and Bt toxins have threatened the efficacy of current management strategies, necessitating the development of alternative pest management methods and technologies. One possible avenue is the use of volatile organic compounds (VOCs) and other secondary metabolites that are produced and sequestered by plants as a response to larval feeding. The effects of conspecific larval feeding on fall armyworm oviposition preferences and larval fitness were examined using two-choice oviposition experiments, larval feeding trials, targeted metabolomics, and VOC analyses. There was a significant preference for oviposition on corn plants that lacked larval feeding damage, and larvae fed tissue from damaged plants exhibited reduced weights and head capsule widths. All larval feeding promoted significantly increased metabolite and VOC concentrations compared to corn plants without any feeding. Metabolite differences were driven primarily by linoleic acid (which is directly toxic to fall armyworm) and tricarboxylic acids. Several VOCs with significantly increased concentrations in damaged corn plants were known oviposition deterrents that warrant further investigation in an integrated pest management context.
Publisher: MDPI AG
Date: 23-02-2023
Abstract: Slugs are cryptic terrestrial pests that target a wide range of crops and are especially damaging to seedlings. Management of these invertebrates mostly relies on synthetic chemistry. These molecules can be efficient against slugs and snails but can be toxic to other organisms (e.g., dogs) and harmful to the environment (e.g., leaching into surface and groundwater). The usage of pathogenic nematodes has been effective in several crops and European countries. A survey was conducted to investigate the presence of natural populations of malacopathogenic nematodes in soybean in the mid-Atlantic region. Slugs were s led in nine fields across Delaware at various distances from the field edges (0 m, 5 m, 10 m, 15 m). Soil cover and soil type were also recorded. Invertebrates were brought back to the laboratory. Slugs were monitored for four weeks, and mortality was classified into one of three categories: (1) death with the presence of nematodes (2) death with the presence of fungi (3) death without the presence of nematodes or fungi. Nematodes associated with slugs were identified based on 18S rRNA sequencing. The distance from the field edge did not impact the number of trapped slugs and the incidence of slug death associated with the presence of nematodes. Overall, nematodes were collected from ca. 20% of the slug cadavers, and most have previously been associated with slugs (ca. 35% of deaths associated with fungi and ca. 45% not associated with nematodes or fungi). The number of captured slugs and slug death associated with the presence of nematodes were positively correlated with ground cover. Soil type impacted both the number of captured slugs and the presence of pathogenic nematodes. This survey provides a first insight into the natural populations of mollusk-associated nematodes in the mid-Atlantic region. This knowledge may contribute to implementing cultural practices favoring these natural enemies of slug pests.
Publisher: Springer Science and Business Media LLC
Date: 11-06-2020
Publisher: Swiss Chemical Society
Date: 26-05-2010
Publisher: Swiss Chemical Society
Date: 30-11-2022
Abstract: It has been estimated that between 40 and 60 % of the assimilated carbon is erted to the roots and released in the rhizosphere in form of root exudates. Root exudates thus define a complex mixture of low and high molecular weight compounds, including carbohydrates, amino acids, organic, and proteins, but also a broad spectrum of specialized molecules, such as flavonoids, glucosinolates, terpenoids, or alkaloids. Root exudates favour soil mineral nutrition, can bind to soil aggregate and in turn modify soil physico-chemical properties, but also mediate plant-plant, plant-microbe, and plant-animal interactions belowground. With this review, we aim to highlight how chemical ecologists have approached the study of root exudates-mediated interactions between plants and their biotic and abiotic surroundings. We do so by presenting a series of study cases for, on one hand, showcasing different methodologies that have been developed to test the activity of different root exudates, and, on the other hand, to show the broad array of interactions mediated by root exudates. Ultimately, we aim to spur further research and collaborations between chemists and ecologists studying belowground chemically-mediated interactions, so as to tackle essential challenges in terms of food security and climate change in the near future.
Publisher: Elsevier BV
Date: 09-2017
Publisher: ACM
Date: 26-10-2008
Publisher: Springer Science and Business Media LLC
Date: 22-12-2009
Publisher: Frontiers Media SA
Date: 30-08-2016
Publisher: Oxford University Press (OUP)
Date: 06-2014
DOI: 10.1603/EN13248
Publisher: Springer Science and Business Media LLC
Date: 02-06-2016
Publisher: The Company of Biologists
Date: 15-07-2010
DOI: 10.1242/JEB.041301
Abstract: The efficacy of natural enemies as biological control agents against insect pests can theoretically be enhanced by artificial selection for high responsiveness to foraging cues. The recent discovery that maize roots damaged by the western corn rootworm (WCR) emit a key attractant for insect-killing nematodes has opened the way to explore whether a selection strategy can improve the control of root pests. The compound in question, (E)-β-caryophyllene, is only weakly attractive to Heterorhabditis bacteriophora, one of the most infectious nematodes against WCR. To overcome this drawback, we used a six-arm below-ground olfactometer to select for a strain of H. bacteriophora that is more readily attracted to (E)-β-caryophyllene. After six generations of selection, the selected strain responded considerably better and moved twice as rapidly towards a (E)-β-caryophyllene source than the original strain. There was a minor trade-off between this enhanced responsiveness and nematode infectiveness. Yet, in subsequent field tests, the selected strain was significantly more effective than the original strain in reducing WCR populations in plots with a maize variety that releases (E)-β-caryophyllene, but not in plots with a maize variety that does not emit this root signal. These results illustrate the great potential of manipulating natural enemies of herbivores to improve biological pest control.
Publisher: Elsevier
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 21-04-2018
DOI: 10.1007/S10886-018-0962-0
Abstract: It has long been thought that most birds do not use volatile cues to perceive their environment. Aside from some scavenging birds, this large group of vertebrates was believed to mostly rely on highly developed vision while foraging and there are relatively few studies exploring bird response to volatile organic compounds. In response to insect herbivory, plants release volatile organic compounds to attract parasitoids and predators of the pests. To test if insectivorous birds use herbivore-induced plant volatiles (HIPV), dispensers emitting a synthetic blend of HIPV typically emitted after insect herbivory were deployed in a maize field along with imitation clay caterpillars. Significantly more imitation insects were attacked by birds when located close to dispensers releasing HIPV than close to dispenser with organic solvent only. Seven times more peck marks, an index of avian predation, were counted on caterpillars in the vicinity of the HIPV dispensers than on insects close to control dispensers. This is the first field demonstration that insectivorous birds cue on HIPV to locate prey in agricultural settings. These results support the growing evidence that foraging birds exploit volatile cues. This more accurate understanding of their behavior will be important when implementing pest management program involving insectivorous birds.
Publisher: Wiley
Date: 21-02-2013
DOI: 10.1111/PBI.12053
Abstract: Genetic manipulation of plant volatile emissions is a promising tool to enhance plant defences against herbivores. However, the potential costs associated with the manipulation of specific volatile synthase genes are unknown. Therefore, we investigated the physiological and ecological effects of transforming a maize line with a terpene synthase gene in field and laboratory assays, both above- and below ground. The transformation, which resulted in the constitutive emission of (E)-β-caryophyllene and α-humulene, was found to compromise seed germination, plant growth and yield. These physiological costs provide a possible explanation for the inducibility of an (E)-β-caryophyllene-synthase gene in wild and cultivated maize. The overexpression of the terpene synthase gene did not impair plant resistance nor volatile emission. However, constitutive terpenoid emission increased plant apparency to herbivores, including adults and larvae of the above ground pest Spodoptera frugiperda, resulting in an increase in leaf damage. Although terpenoid overproducing lines were also attractive to the specialist root herbivore Diabrotica virgifera virgifera below ground, they did not suffer more root damage in the field, possibly because of the enhanced attraction of entomopathogenic nematodes. Furthermore, fewer adults of the root herbivore Diabrotica undecimpunctata howardii were found to emerge near plants that emitted (E)-β-caryophyllene and α-humulene. Yet, overall, under the given field conditions, the costs of constitutive volatile production overshadowed its benefits. This study highlights the need for a thorough assessment of the physiological and ecological consequences of genetically engineering plant signals in the field to determine the potential of this approach for sustainable pest management strategies.
Publisher: Springer Science and Business Media LLC
Date: 05-05-2012
Publisher: MDPI AG
Date: 16-03-2022
Abstract: Winter oilseed rape (Brassica napus) is a global major crop used for the production of vegetable oil. Typically sown in late summer and grown throughout winter and spring, it allows for interesting cultural practices, such as frost-sensitive intercropping with companion plants. This practice not only provides nitrogen resources much needed by the crop in the spring, but companion plants can also prevent weed growth in autumn, thereby reducing common herbicide use. Additionally, intercropping has the potential to protect the crop from insect pests. During winter 2019–2020, B. napus was grown alone (i.e., as a control) or intercropped with a mixture of faba bean (Vicia faba) and grass pea (Lathyrus sativus) because of the unusually clement weather conditions, the faba bean did not freeze, which allowed for the evaluation of the impact of these companion plants on the insect pest complex in spring. Insect damage by the beetles Psylliodes chrysocephala, Ceutorhynchus napi, and Brassicogethes aeneus was assessed in both treatments. The larval density of P. chrysocephala was significantly lower in the crop grown with service plants. Egg laying and damage by C. napi were significantly reduced when B. napus was intercropped, and the number of B. aeneus captured was significantly lower in the presence of service plants than in the control. Moreover, the yield from oilseed rape was significantly higher in the part of the field with service plants than in the pure crop control. The underlying mechanisms are only partially understood, but intercropping winter oilseed rape with frost-resistant service plants seems to be an ecologically sound practice with a very high level of potential to reduce insect pest pressure and increase crop yield. This may eventually reduce our reliance on chemical inputs in one of the most treated crops.
Publisher: Springer Science and Business Media LLC
Date: 09-2015
DOI: 10.1007/S10886-015-0623-5
Abstract: Root exudates can play an important role in plant-nematode interactions. Recent studies have shown that the root cap exudates obtained from several plant species trigger a state of dormancy or quiescence in various genera of nematodes. This phenomenon is not only of fundamental ecological interest, but also has application potential if the plant-produced compound(s) could be used to control harmful nematodes or help to prolong the shelf-life of beneficial entomopathogenic nematodes (EPNs). The identification of the compound(s) involved in quiescence induction has proven to be a major challenge and requires large amounts of active material. Here, we present a high-throughput method to obtain bioactive root extracts from flash-frozen root caps of green pea and maize. The root cap extract obtained via this method was considerably more potent in inducing quiescence than exudate obtained by a previously used method, and consistently induced quiescence in the EPN Heterorhabditis megidis, even after a 30-fold dilution. Extracts obtained from the rest of the root were equally effective in inducing quiescence. Infective juveniles (IJs) of H. megidis exposed to these extracts readily recovered from their quiescent state as soon as they were placed in moist soil, and they were at least as infectious as the IJs that had been stored in water. Excessive exposure of IJs to air interfered with the triggering of quiescence. The implications of these results and the next steps towards identification of the quiescence-inducing compound(s) are discussed from the perspective of applying EPN against soil-dwelling insect pests.
Publisher: Springer Science and Business Media LLC
Date: 29-04-2008
DOI: 10.1007/S10886-008-9467-6
Abstract: Maize roots respond to feeding by larvae of the beetle Diabrotica virgifera virgifera by releasing (E)-beta-caryophyllene. This sesquiterpene, which is not found in healthy maize roots, attracts the entomopathogenic nematode Heterorhabditis megidis. In sharp contrast to the emission of virtually only this single compound by damaged roots, maize leaves emit a blend of numerous volatile organic compounds in response to herbivory. To try to explain this difference between roots and leaves, we studied the diffusion properties of various maize volatiles in sand and soil. The best diffusing compounds were found to be terpenes. Only one other sesquiterpene known for maize, alpha-copaene, diffused better than (E)-beta-caryophyllene, but biosynthesis of the former is far more costly for the plant than the latter. The diffusion of (E)-beta-caryophyllene occurs through the gaseous rather than the aqueous phase, as it was found to diffuse faster and further at low moisture level. However, a water layer is needed to prevent complete loss through vertical diffusion, as was found for totally dry sand. Hence, it appears that maize has adapted to emit a readily diffusing and cost-effective belowground signal from its insect-damaged roots.
Publisher: Wiley
Date: 09-01-2018
DOI: 10.1111/JEN.12480
Publisher: Springer Science and Business Media LLC
Date: 18-03-2008
Publisher: Oxford University Press (OUP)
Date: 27-08-2015
DOI: 10.1093/JXB/ERU345
Publisher: Frontiers Media SA
Date: 15-08-2017
Publisher: Wiley
Date: 09-12-2016
Publisher: Springer International Publishing
Date: 2015
Publisher: Wiley
Date: 16-05-2011
DOI: 10.1111/J.1365-3040.2011.02327.X
Abstract: Plants attacked by leaf herbivores release volatile organic compounds (VOCs) both locally from the wounded site and systemically from non-attacked tissues. These volatiles serve as attractants for predators and parasitoids. This phenomenon is well described for plant leaves, but systemic induction of VOCs in the roots has remained unstudied. We assessed the spatial and temporal activation of the synthesis and release of (E)-β-caryophyllene (EβC) in maize roots upon feeding by larvae of Diabrotica virgifera virgifera, as well as the importance of systemically produced EβC for the attraction of the entomopathogenic nematode Heterorhabditis megidis. The production of EβC was found to be significantly stronger at the site of attack than in non-attacked tissues. A weak, but significant, increase in transcriptional activity of the EβC synthase gene tps23 and a corresponding increase in EβC content were observed in the roots above the feeding site and in adjacent roots, demonstrating for the first time that herbivory triggers systemic production of a volatile within root systems. In belowground olfactometers, the nematodes were significantly more attracted towards local feeding sites than systemically induced roots. The possible advantages and disadvantages of systemic volatile signalling in roots are discussed.
Publisher: Springer Science and Business Media LLC
Date: 20-06-2012
Publisher: Informa UK Limited
Date: 11-2010
No related grants have been discovered for Ivan Hiltpold.