Browsing by Author "Blanco-Perez, Ruben"
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- Combined field inoculations of pseudomonas bacteria, arbuscular mycorrhizal fungi, and entomopathogenic nematodes and their effects on wheat performancePublication . Imperiali, Nicola; Chiriboga, Xavier; Schlaeppi, Klaus; Fesselet, Marie; Villacres, Daniela; Jaffuel, Geoffrey; Bender, S. Franz; Dennert, Francesca; Blanco-Perez, Ruben; van der Heijden, Marcel G. A.; Maurhofer, Monika; Mascher, Fabio; Turlings, Ted C. J.; Keel, Christoph J.; Campos-Herrera, RaquelIn agricultural ecosystems, pest insects, pathogens, and reduced soil fertility pose major challenges to crop productivity and are responsible for significant yield losses worldwide. Management of belowground pests and diseases remains particularly challenging due to the complex nature of the soil and the limited reach of conventional agrochemicals. Boosting the presence of beneficial rhizosphere organisms is a potentially sustainable alternative and may help to optimize crop health and productivity. Field application of single beneficial soil organisms has shown satisfactory results under optimal conditions. This might be further enhanced by combining multiple beneficial soil organisms, but this remains poorly investigated. Here, we inoculated wheat plots with combinations of three beneficial soil organisms that have different rhizosphere functions and studied their effects on crop performance. Plant beneficial Pseudomonas bacteria, arbuscular mycorrhizal fungi (AMF), and entomopathogenic nematodes (EPN), were inoculated individually or in combinations at seeding, and their effects on plant performance were evaluated throughout the season. We used traditional and molecular identification tools to monitor their persistence over the cropping season in augmented and control treatments, and to estimate the possible displacement of native populations. In three separate trials, beneficial soil organisms were successfully introduced into the native populations and readily survived the field conditions. Various Pseudornonas, mycorrhiza, and nematode treatments improved plant health and productivity, while their combinations provided no significant additive or synergistic benefits compared to when applied alone. EPN application temporarily displaced some of the native EPN, but had no significant long-term effect on the associated food web. The strongest positive effect on wheat survival was observed for Pseudomonas and AMF during a season with heavy natural infestation by the frit fly, Oscinella frit, a major pest of cereals. Hence, beneficial impacts differed between the beneficial soil organisms and were most evident for plants under biotic stress. Overall, our findings indicate that in wheat production under the test conditions the three beneficial soil organisms can establish nicely and are compatible, but their combined application provides no additional benefits. Further studies are required, also in other cropping systems, to fine-tune the functional interactions among beneficial soil organisms, crops, and the environment.
- Cutaneous excreta of the earthworm Eisenia fetida (Haplotaxida: Lumbricidae) might hinder the biological control performance of entomopathogenic nematodesPublication . Chelkha, Maryam; Blanco-Perez, Ruben; Bueno-Pallero, Francisco Angel; Amghar, Souad; El Harti, Abdellatif; Campos-Herrera, RaquelEarthworms enhance soil structure, the decomposition of organic matter and the dissemination of beneficial soil organisms such as the entomopathogenic nematodes (EPNs). Nevertheless, the effects of earthworm feeding behavior or cutaneous excreta (CEx) on the performance of EPNs as biological control agents is poorly understood. We hypothesized that the presence of earthworms or their excreta reduces EPN fitness, measured in terms of pathogenicity and reproductive success. In laboratory experiments we first evaluated the killing ability of EPNs against Galleria mellonella (Lepidoptera: Pyralidae) larvae when inoculated in autoclaved soil alone or in combination with the earthworm Eisenia fetida (Haplotaxida: Lumbricidae) or their excreta. We also evaluated EPN efficacy and reproduction when exposed to CEx derived from E. fetida at two nematode concentrations (1.5 and 10 IJs/cm(2)). For both experiments, we tested four steinernematids (Steinernema carpocapsae, S. feltiae, S. glaseri, and S. khuongi) and two heterorhabditids (Heterorhabditis bacteriophora and H. zealandica). The presence of earthworms or their excreta resulted in significant reduction of the larval mortality caused by some of the steinernematids at certain timings depending of the species (P < 0.015), while heterorhabditids were mainly not affected. Both S. feltiae and H. zealandica progeny production was significantly reduced (P < 0.01) when exposed to CEx. Hence, we showed that the presence of CEx might alter the biocontrol performance of certain EPN species, especially steinernematids bigger than 600 mu m in size (S. feltiae, S. glaseri, and S. khoungi), by affecting their pathogenicity and reproductive success.
- Prevalence and activity of entomopathogenic nematodes and their antagonists in soils that are subject to different agricultural practicesPublication . Jaffuel, Geoffrey; Mader, Paul; Blanco-Perez, Ruben; Chiriboga, Xavier; Fliessbach, Andreas; Turlings, Ted C. J.; Campos-Herrera, RaquelAgricultural management practices can modify soil properties in ways that may disrupt the abundance and activity of beneficial organisms in the soil. We assessed the impact of different soil management practices on entomopathogenic nematodes (EPN), which have great potential as biological control agents against root-feeding insects. Soils were sampled during spring and autumn 2013 in all 96 plots of a long-term Swiss field trial (DOK experiment). By combining a traditional insect-baiting technique and real-time qPCR analyses, we identified and quantified over 20 soil-dwelling species (or genera). This allowed us to investigate how communities of natural EPN populations and their associated natural enemies and competitors are affected by (i) three crop types (wheat, maize and grass-clover ley) and (ii) farming systems, i.e. conventional, organic and biodynamic, which differed in fertilization, and pesticide use. We also determined the effects on soils' microbial biomass in terms of carbon (C-mic) and nitrogen (N-mic) and applied spatial distribution analysis (SADIE) to uncover patterns of aggregations and associations of the study organisms. Although manure based farming systems increased microbial biomass, the systems did not influence the presence of EPN or their antagonists. EPN was more abundant in winter-wheat plots than in maize and grass-clover ley plots. Overall, very low numbers of EPN were recorded, implying that their natural presence would not be sufficient to have a satisfactory suppressive effect on root-feeding pests and the application of EPN would therefore be an appropriate measure to protect yields in case of root pest outbreaks. (C) 2016 Elsevier B.V. All rights reserved.