Induced Tomato Plant Resistance Against Tetranychus urticae Triggered by the Phytophagy of Nesidiocoris tenuis

The zoophytophagous predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is capable of inducing plant defenses in tomato due to its phytophagous behavior. These induced defenses, which include the release of herbivore-induced plant volatiles (HIPVs), have been proven to affect the oviposition behavior and reduce the subsequent performance of some tomato pests. However, the effect of induction of plant defenses by N. tenuis on the preference, development, and reproduction of the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) remains unknown. In this research, T. urticae did not show preference for the odor source emitted by intact tomato plants when compared with N. tenuis-punctured plants and jasmonic acid (JA) deficient mutant tomato plants. Furthermore, the number of eggs laid by T. urticae on intact tomato plants or on N. tenuis-punctured plants was similar. However, in a greenhouse experiment conducted to evaluate whether the defense induction mediated by N. tenuis had an effect on T. urticae the infestation of T. urticae was significantly reduced by 35% on those plants previously activated by N. tenuis when compared to the control. The expression of a JA-responsive gene that was upregulated and the transcription of the plant protein inhibitor II was higher on activated plants relative to the control. These results can serve as a basis for the development of new management strategies for T. urticae based on plant defense mechanisms induced from the phytophagous behavior of N. tenuis

Silenciamiento de genes diana de Delottococcus aberiae DeLotto (Hemiptera: Pseudococcidae) mediante tecnología RNAi

El RNA de interferencia (RNAi) es una de las herramientas biotecnológicas con mayor potencial en la protección de cultivos frente a insectos plagas. Con esta técnica de silenciamiento postranscripcional se puede bloquear la expresión de genes diana de interés al destruir eficazmente su correspondiente RNA mensajero (mRNA). En los últimos años se han logrado avances significativos en varios aspectos del mecanismo de silenciamiento génico postranscripcional mediado por moléculas de RNA de doble cadena (dsRNA). En la actualidad el mundo científico se encuentra en disposición de poder transferir y aplicar de manera práctica esta potente herramienta al control biológico de plagas

Orius laevigatus Induces Plant Defenses in Sweet Pepper

Pest management in protected sweet pepper crops primarily relies on biological control strategies. The release of the phytoseiid Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) and the anthocorid Orius laevigatus Fieber (Hemiptera: Anthocoridae) provides effective control of the two key pests of this crop, the thrips Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) and the whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) (Sanchez et al., 2000; Calvo et al., 2009; van der Blom et al., 2009). A part of their direct effect on pest predation, zoophytophagous predators may induce defensive plant responses due to their plant feeding behaviour which involves the release of diverse volatiles through different pathways that are triggered by phytohormones (De Puysseleyr et al., 2011; Naselli et al., 2016; Pappas et al., 2015, 2016; Pérez-Hedo et al., 2015a,b). These responses may result in the repellence or attraction of pests and natural enemies. It is hence hypothesized that O. laevigatus would be able to induce plant responses in sweet pepper as has been demonstrated in other plantzoophytophage systems. As a first step to better understand the interaction between O. laevigatus and sweet pepper, the behavior of O. laevigatus on the plants was studied and plant feeding behaviour quantified to compare general behaviors. Orius laevigatus spends the majority of its time (38%) feeding on apical meristems and apical fresh leaves, which were also preferred residence locations (Bouagga et al., 2017)

Eliciting Plant Defenses Through Herbivore-Induced Plant Volatiles’ Exposure in Sweet Peppers

Insect herbivory activates plant defense mechanisms and releases a blend of herbivoreinduced plant volatiles (HIPVs). These volatile compounds may be involved in plant-plant communication and induce defense response in undamaged plants. In this work, we investigated whether the exposure of sweet pepper plants to HIPVs [(Z)-3-hexenol, (Z)- 3-hexenyl acetate, (Z)-3-hexenyl propanoate, (Z)-3-hexenyl butanoate, hexyl butanoate, methyl salicylate and methyl jasmonate] activates the sweet pepper immune defense system. For this, healthy sweet pepper plants were individually exposed to the each of the above mentioned HIPVs over 48 h. The expression of jasmonic acid and salicylic acid related genes was quantified. Here, we show that all the tested volatiles induced plant defenses by upregulating the jasmonic acid and salicylic acid signaling pathway. Additionally, the response of Frankliniella occidentalis, a key sweet pepper pest, and Orius laevigatus, the main natural enemy of F. occidentalis, to HIPV-exposed sweet pepper plants were studied in a Y-tube olfactometer. Only plants exposed to (Z)-3-hexenyl propanoate and methyl salicylate repelled F. occidentalis whereas O. laevigatus showed a strong preference to plants exposed to (Z)-3-hexenol, (Z)-3-hexenyl propanoate, (Z)-3-hexenyl butanoate, methyl salicylate and methyl jasmonate. Our results show that HIPVs act as elicitors to sweet pepper plant defenses by enhancing defensive signaling pathways. We anticipate our results to be a starting point for integrating HIPVs-based approaches in sweet pepper pest management systems which may provide a sustainable strategy to manage insect pests in horticultural plants

The olfactive responses of Tetranychus urticae natural enemies in citrus depend on plant genotype, prey presence, and their diet specialization

[EN] Sour orange, Citrus aurantium, displays higher constitutive and earlier inducible direct defenses against the two-spotted spider mite, Tetranychus urticae, than Cleopatra mandarin, Citrus reshni. Moreover, herbivore-induced plant volatiles (HIPVs) produced by sour orange upon infestation can induce resistance in Cleopatra mandarin but not vice versa. Because the role of these HIPVs in indirect resistance remains ignored, we have carried out a series of behavioral assays with three predatory mites with different levels of specialization on this herbivore, from strict entomophagy to omnivory. We have further characterized the volatile blend associated with T. urticae, which interestingly includes the HIPV methyl salicylate, as well as that produced by induced Cleopatra mandarin plants. Although a preference for less defended plants with presumably higher prey densities (i.e., C. reshni) was expected, this was not always the case. Because predators' responses changed with diet width, with omnivore predators responding to both HIPVs and prey-related odors and specialized ones mostly to prey, our results reveal that these responses depend on plant genotype, prey presence and predator diet specialization. As the different volatile blends produced by infested sour orange, induced Cleopatra mandarin and T. urticae itself are attractive to T. urticae natural enemies but not to the herbivore, they may provide clues to develop new more sustainable tools to manipulate these agriculturally relevant species.The research leading to these results was partially funded by the Spanish Ministry of Economy and Competitiveness (AGL2014-55616-C3; AGL2015-64990-2R). The authors thank M. Piquer (UJI) for technical assistance. MC received a pre-doctoral fellowship from the Spanish Ministry of Economy and Competitiveness (BES-2015-074570), and MP was the recipient of a research fellowship from INIA, Spain (subprogram DOC INIA-CCAA).Cabedo López, M.; Cruz-Miralles, J.; Vacas, S.; Navarro-Llopis, V.; Pérez-Hedo, M.; Flors, V.; Jaques, JA. (2019). The olfactive responses of Tetranychus urticae natural enemies in citrus depend on plant genotype, prey presence, and their diet specialization. Journal of Pest Science. 92(3):1165-1177. https://doi.org/10.1007/s10340-019-01107-7S1165117792