Abstract
The beneficial effects of direct predation by zoophytophagous biological control agents (BCAs), such as the mirid bug Nesidiocoris tenuis, are well-known. However, the benefits of zoophytophagous BCAs’ relation with host plants, via induction of plant defensive responses, have not been investigated until recently. To date, only the females of certain zoophytophagous BCAs have been demonstrated to induce defensive plant responses in tomato plants. The aim of this work was to determine whether nymphs, adult females, and adult males of N. tenuis are able to induce defense responses in tomato plants. Compared to undamaged tomato plants (i.e., not exposed to the mirid), plants on which young or mature nymphs, or adult males or females of N. tenuis fed and developed were less attractive to the whitefly Bemisia tabaci, but were more attractive to the parasitoid Encarsia formosa. Female-exposed plants were more repellent to B. tabaci and more attractive to E. formosa than were male-exposed plants. When comparing young- and mature-nymph-exposed plants, the same level of repellence was obtained for B. tabaci, but mature-nymph-exposed plants were more attractive to E. formosa. The repellent effect is attributed to the signaling pathway of abscisic acid, which is upregulated in N. tenuis-exposed plants, whereas the parasitoid attraction was attributed to the activation of the jasmonic acid signaling pathway. Our results demonstrate that all motile stages of N. tenuis can trigger defensive responses in tomato plants, although these responses may be slightly different depending on the stage considered.
Highlights
Plants are able to defend themselves from arthropods, pathogens and, in general, from biotic and abiotic stress conditions [1,2,3]
When plants exposed to young (NI and NII) or mature nymphs (NIV and NV) of N. tenuis were compared to undamaged plants, a clear preference of B. tabaci for undamaged plants was observed (χ2 = 5.000, p = 0.0253 and χ2 = 7.200, p = 0.0073, respectively, Figures 1a and 2a)
Our results demonstrate the direct relationship between N. tenuis’ plant feeding and defense induction in tomato
Summary
Plants are able to defend themselves from arthropods, pathogens and, in general, from biotic and abiotic stress conditions [1,2,3]. To this end, plants activate a cascade of events that include transcriptome changes of some of the genes involved in the biosynthesis of phytohormones that lead—directly and indirectly—to defensive responses [4,5]. Depending on the herbivore’s feeding habits (chewing, phloem, or cell content feeders), different hormone-related signaling pathways are triggered [9,10,11,12,13]. JA may be induced by cell content feeders such as thrips (Thysanoptera: Thripidae) and spider mites (Acari: Tetranychidae) [8]
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