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Fereres A.,ICA CSIC | Penaflor M.F.G.V.,Federal University of Lavras | Penaflor M.F.G.V.,University of Sao Paulo | Favaro C.F.,University Estadual Of Santa Cruz | And 6 more authors.
Viruses | Year: 2016

Virus infection frequently modifies plant phenotypes, leading to changes in behaviour and performance of their insect vectors in a way that transmission is enhanced, although this may not always be the case. Here, we investigated Bemisia tabaci response to tomato plants infected by Tomato chlorosis virus (ToCV), a non-circulative-transmitted crinivirus, and Tomato severe rugose virus (ToSRV), a circulative-transmitted begomovirus. Moreover, we examined the role of visual and olfactory cues in host plant selection by both viruliferous and non-viruliferous B. tabaci. Visual cues alone were assessed as targets for whitefly landing by placing leaves underneath a Plexiglas plate. A dual-choice arena was used to assess whitefly response to virus-infected and mock-inoculated tomato leaves under light and dark conditions. Thereafter, we tested the whitefly response to volatiles using an active air-flow Y-tube olfactometer, and chemically characterized the blends using gas chromatography coupled to mass spectrometry. Visual stimuli tests showed that whiteflies, irrespective of their infectious status, always preferred to land on virus-infected rather than on mock-inoculated leaves. Furthermore, whiteflies had no preference for either virus-infected or mock-inoculated leaves under dark conditions, but preferred virus-infected leaves in the presence of light. ToSRV-infection promoted a sharp decline in the concentration of some tomato volatiles, while an increase in the emission of some terpenes after ToCV infection was found. ToSRV-viruliferous whiteflies preferred volatiles emitted from mock-inoculated plants, a conducive behaviour to enhance virus spread, while volatiles from ToCV-infected plants were avoided by non-viruliferous whiteflies, a behaviour that is likely detrimental to the secondary spread of the virus. In conclusion, the circulative persistent begomovirus, ToSRV, seems to have evolved together with its vector B. tabaci to optimise its own spread. However, this type of virus-induced manipulation of vector behaviour was not observed for the semi persistent crinivirus, ToCV, which is not specifically transmitted by B. tabaci and has a much less intimate virus-vector relationship. © 2016 by the author; licensee MDPI, Basel, Switzerland.

Dader B.,ICA CSIC | Legarrea S.,ICA CSIC | Moreno A.,ICA CSIC | Ambros C.M.,ICA CSIC | And 4 more authors.
Acta Horticulturae | Year: 2014

Vegetable crops suffer from a range of economically damaging insect-pests and insect-transmitted virus diseases. Current control practice involves intensive spraying of insecticides, which may have undesirable effects on the environment, growers and consumers. Our goal is to develop a new physical-chemical barrier treated with fast acting insecticides to reduce the incidence of pests and insect transmitted virus diseases in protected crops. The new approach is based on a slow release insecticide-treated net with relatively large holes size to improve airflow and ventilation inside the protected environment while maintaining the protection from insect pests. Such net could be placed on an entire net house or on the sides and ventilation openings of a conventional plastic film covered greenhouse, as a barrier against insect pests. A series of laboratory experiments using vertical glass tube chambers divided by insecticide-treated nets were conducted. The nets tested had various combinations of insecticides, mesh sizes, colours and UV blockers. One of the laboratory-selected nets was tested under field conditions on a tunnel-type greenhouse under a very high pest infestation pressure. Cucumber plants previously infected with Cucumber mosaic virus and Cucurbit aphid-borne yellow virus were artificially infested with Bemisia tabaci and Aphis gossypii on the outer sides of the tunnel. The selected insecticide-treated nets effectively blocked the invasion of A. gossypii and reduced the incidence of virus-infected cucumber plants grown inside the tunnel compared to plants covered with similar nets of the same mesh size with no insecticide. However, the insecticide-treated nets failed to control B. tabaci.

Portillo M.,University of Castilla - La Mancha | Cabrera J.,University of Castilla - La Mancha | Lindsey K.,Durham University | Topping J.,Durham University | And 9 more authors.
New Phytologist | Year: 2013

Root-knot nematodes (RKNs) induce giant cells (GCs) from root vascular cells inside the galls. Accompanying molecular changes as a function of infection time and across different species, and their functional impact, are still poorly understood. Thus, the transcriptomes of tomato galls and laser capture microdissected (LCM) GCs over the course of parasitism were compared with those of Arabidopsis, and functional analysis of a repressed gene was performed. Microarray hybridization with RNA from galls and LCM GCs, infection-reproduction tests and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) transcriptional profiles in susceptible and resistant (Mi-1) lines were performed in tomato. Tomato GC-induced genes include some possibly contributing to the epigenetic control of GC identity. GC-repressed genes are conserved between tomato and Arabidopsis, notably those involved in lignin deposition. However, genes related to the regulation of gene expression diverge, suggesting that diverse transcriptional regulators mediate common responses leading to GC formation in different plant species. TPX1, a cell wall peroxidase specifically involved in lignification, was strongly repressed in GCs/galls, but induced in a nearly isogenic Mi-1 resistant line on nematode infection. TPX1 overexpression in susceptible plants hindered nematode reproduction and GC expansion. Time-course and cross-species comparisons of gall and GC transcriptomes provide novel insights pointing to the relevance of gene repression during RKN establishment. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Flores-Renteria D.,CSIC - National Museum of Natural Sciences | Curiel Yuste J.,CSIC - National Museum of Natural Sciences | Rincon A.,CSIC - Institute of Agricultural Sciences | Brearley F.Q.,Manchester Metropolitan University | And 2 more authors.
Microbial Ecology | Year: 2015

Ecological transformations derived from habitat fragmentation have led to increased threats to above-ground biodiversity. However, the impacts of forest fragmentation on soils and their microbial communities are not well understood. We examined the effects of contrasting fragment sizes on the structure and functioning of soil microbial communities from holm oak forest patches in two bioclimatically different regions of Spain. We used a microcosm approach to simulate the annual summer drought cycle and first autumn rainfall (rewetting), evaluating the functional response of a plant-soil-microbial system. Forest fragment size had a significant effect on physicochemical characteristics and microbial functioning of soils, although the diversity and structure of microbial communities were not affected. The response of our plant-soil-microbial systems to drought was strongly modulated by the bioclimatic conditions and the fragment size from where the soils were obtained. Decreasing fragment size modulated the effects of drought by improving local environmental conditions with higher water and nutrient availability. However, this modulation was stronger for plant-soil-microbial systems built with soils from the northern region (colder and wetter) than for those built with soils from the southern region (warmer and drier) suggesting that the responsiveness of the soil-plant-microbial system to habitat fragmentation was strongly dependent on both the physicochemical characteristics of soils and the historical adaptation of soil microbial communities to specific bioclimatic conditions. This interaction challenges our understanding of future global change scenarios in Mediterranean ecosystems involving drier conditions and increased frequency of forest fragmentation. © 2015, Springer Science+Business Media New York.

San Martin C.,ICA CSIC | Martin J.M.,ICA CSIC | Campos D.,ICA CSIC | Andujar D.,ICA CSIC | And 2 more authors.
Precision Agriculture 2013 - Papers Presented at the 9th European Conference on Precision Agriculture, ECPA 2013 | Year: 2013

A series of scenarios were assessed by simulating various weed decision thresholds (WDT) and different weed detection and herbicide application resolutions. Variable responses were obtained depending on the spatial distribution pattern of the weed. In the case of a patchy distributed species (Sorghum halepense), errors in spraying decision increased as the resolution increased and the WDT decreased. In contrast, in a uniformly distributed species (Abutilon theophrasti), errors in spraying decision increased when both the resolution and the WDT increased. Weed decision threshold was essential in determining the suitability of patch spraying. Consequently, site-specific control would depend primarily on the ability to detect low weed densities.

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