Plant defences, spider mites and web affecting arthropod responses to tomato plants

• Ano de defesa: 2017
• Autor(a) principal: Dias, Cleide Rosa
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Tomate - Resistência a doenças e pragas; Tetranychus evansi; Tomate - Mecanismos de defesa; Entomologia Agrícola
• Link de acesso: https://locus.ufv.br//handle/123456789/27285

Plants developed a wide range of defences in response to herbivore attack. These defences can affect herbivores directly, for example, through production of defensive compounds and proteins that reduce herbivore performance; or indirectly, by attracting the natural enemies of the herbivores. The spider mite Tetranychus urticae, for example, induces defences in tomato plants which decrease herbivorous mites performance and attract predatory mites. Moreover, some herbivores have adapted and are able to suppress plant defences, such as the spider mite Tetranychus evansi. Additionally, T. evansi cover the plant with a dense web, which among other functions, avoid competitors to profit from the suppressed defences. In this thesis, | studied the direct and indirect effects of changes in plant defence due infestation of the spider mites T. urticae and T. evansi, as well as their presence and their web, on other arthropods that occur in tomato plants. Studies that aim to investigate the effect of plant defences on herbivores, are commonly performed through evaluation of herbivores performance on treated plants, being done on whole plants or plant parts. Both methods have pros and cons, and the choice of which one to use depends on the system being studied: research question, organism and plant. Thus, in the first chapter, | investigated the effects of plants with defences induced and suppressed on the subsequent performance of an herbivore, on whole plants and on leaf discs. The method of evaluation and plant treatment affected the performance of T. evansi. However, there was no effect of the method on T. evansi response to plant defences: the oviposition rate of T. evansi was lower on plants infested with the inducer T. urticae than on plants infested with the suppressor T. evansi and uninfested plants on both methods, whole plants and leaf discs. In the second chapter, | investigated the attraction of arthropods to plants with defences suppressed by T. evansi and induced by T. urticae in an outdoor area, with infested plants covered or not with spider mite web. The plant defence interfered on the host choice of some herbivores, but not on the choice of natural enemies. The presence of web in combination with plant defences interfered on whiteflies host plant choice: plants with defences suppressed were more attractive to whiteflies in absence of web, but not when plants were covered by spider mite web. In the third chapter, | investigated the effect of indirect and direct plant defences and spider mite web on host plant choice and performance of the whitefly B. tabaci. Whiteflies preferred plants where they had higher survival of juvenile and recently emerged adults, that was uninfested and plants with defence suppressed without web. Finally, in the fourth chapter, we investigated whether thechanges in tomato plant defences through infestation with the defence-inducer T. urticae and the defence-suppressor T. evansi, as well as the presence of the spider mites and their web, affect the plant host preference and performance of Frankliniella occidentalis. The presence of the spider mites and the induction of plant defences did not affect the survival and performance of juveniles of F. occidentalis. Nevertheless, the presence of spider mite web on plants infested with T. evansi made these plants more attractive to F. occidentalis, but did not affect the performance and survive of juveniles. In conclusion, the results showed that both whole plants and leaf discs can be used for studies that aim to evaluate effects of tomato defences on the spider mites. Also, tomato plants with defences suppressed or induced by the spider mites can affect the host plant preference and performance of whiteflies but not of thrips. Likewise, the combination of web with plant defences also interfered on thrips and whiteflies host choice.