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.

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Resumo: A Senna siamea, originaria da Tailândia, é uma espécie de porte arbóreo pertencente à família das Fabaceae e subfamília Caesalpinoideae, e conhecida vulgarmente por Cássia-de-sião. É muito utilizada na arborização urbana. Como ainda são escassas as pesquisas sobre as sementes da espécie, o objetivo deste trabalho foi caracterizar a biometria dos frutos e sementes de Senna siamea. Foram utilizados 100 frutos e 200 sementes, sendo avaliadas nos frutos as características: comprimento, peso, diâmetro e número de sementes por vargem; e nas sementes: o peso e o diâmetro. Para cada variável foram calculados a média, variância, desvio padrão, amplitude total, e amplitude de classes. Os frutos de Senna siamea apresentam comprimento semelhante entre si com media 23,7 mm, já para as demais características avaliadas apresentam comportamento assimétrico com média de 4,20 g para o peso, 13,80 mm de diâmetro e média de 20,66 sementes por fruto. Já para as sementes o que se observou foi uma distribuição assimétrica, pesando em média 0,03 g, e com diametro de 8,04 mm. A Senna siamea apresenta uma distribuição assimétrica tanto de frutos como de sementes.

1. In insect-resistant populations, adaptive fitness is intimately related to the physiological responses of males and females to different stressors.2. By using laboratory-selected imidacloprid-resistant individuals of the Neotropical brown stink bug Euschistus heros, one of the most prevalent pests in soybean fields in the Neotropical region, we evaluated whether resistance to imidacloprid (synergized by piperonyl butoxide-PBO) would differentially affect the longevity, body mass and respiratory responses of E. heros males and females.3. We used an imidacloprid-susceptible E. heros strain (ImiSusc), whose individuals were reared under controlled and imidacloprid-free conditions for over a decade, to select the PBO-synergized imidacloprid-resistant strain (ImiPBOSel). 4. After eight generations using PBO-synergized imidacloprid, our results revealed that resistant individuals exposed only to dry residues of imidacloprid (tarsal contact) could survive at concentrations as high as 168 μg a.i./cm 2 , which is equivalent to 40-fold the label recommendation for field applications. Furthermore, ImiPBOSel males and females exhibited higher longevity, higher body mass and elevated respiratory activity than ImiSusc individuals. 5. Altogether, the findings described here showed that imidacloprid resistance can select E. heros individuals with better metabolic capacities, which can complicate the management of this pest under field conditions.