Eliciting tomato plant defenses by exposure to herbivore induced plant volatiles

Abstract

When zoophytophagous mirids (Hemiptera: Miridae) feed on tomato plants they activate both direct and indirect defense mechanisms, which include the release of herbivore induced plant volatiles (HIPVs). HIPVs are capable of activating defense mechanisms in healthy neighboring plants. In this work, we investigated which of these mirid-induced HIPVs are responsible for inducing plant defenses. Healthy tomato plants were individually exposed to eight HIPVs [1-hexanol, (Z)-3-hexenol, (Z)-3-hexenyl acetate, (Z)-3-hexenyl propanoate, (Z)-3-hexenyl butanoate, hexyl butanoate, methyl jasmonate and methyl salicylate] for 24 hours.Then, the expression level of defensive genes was quantified. All HIPVs led to increased expression of defensive genes by the plant when compared to unexposed tomato plants. In a further step, (Z)-3-hexenyl propanoate and methyl salicylate were selected to study the response of four tomato key pests and one natural enemy to tomato plants previously exposed to both HIPVs relative to unexposed control plants. Plants previously exposed to both HIPVs were repellent to Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) and Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), attractive to the parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) and indifferent to Tetranychus urticae Koch (Acari: Tetranychidae). The volatiles emitted by plants previously exposed to both selected volatiles were also determined. Increased levels of C5 and C6 fatty acid-derived volatile compounds and β-ionone were detected, confirming that both HIPVs significantly activated the lipoxygenase pathway. These results are the starting point to advance the use of volatile compounds as defense elicitors in tomato crops.

Does the dose make the poison? Neurotoxic insecticides impair predator orientation and reproduction even at low concentrations

“…Despite this drawback, IPM programs still rely on the biological control provided by N. tenuis . Therefore, the predator can be often exposed to organic and/or synthetic insecticides routinely adopted in these programs 42–45 …”

“…Therefore, the predator can be often exposed to organic and/or synthetic insecticides routinely adopted in these programs. [42][43][44][45] Earlier studies investigated the impact of insecticides on N. tenuis in terms of lethal and sublethal effects, by exposing N. tenuis adults to synthetic and organic neurotoxic compounds via different exposure routes (i.e., contaminated prey, direct spray and residual contact). 27,28,46,47 Nevertheless, most studies investigated only the maximum label rate of these compounds.…”

“…Therefore, the predator can be often exposed to organic and/or synthetic insecticides routinely adopted in these programs. 42 , 43 , 44 , 45 …”

The Endophyte Trichoderma asperellum M2RT4 Induces the Systemic Release of Methyl Salicylate and (Z)-jasmone in Tomato Plant Affecting Host Location and Herbivory of Tuta absoluta

“…The repellent effect of methyl salicylate has previously been reported in aphids and the glasshouse whitefly ( Xu et al, 2018 ; Conboy et al, 2020 ). Methyl salicylate has also being shown to induce defenses against T. absoluta ( Pérez-Hedo et al, 2021 ) and serve as an oviposition attractant for the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) ( Yactayo-Chang et al, 2021 ).…”

Two in one: the neotropical mirid predator Macrolophus basicornis increases pest control by feeding on plants

“…Thus, evaluation of whether M. basicornis and Encarsia inaron trigger chemosensory responses to each compound identified and the capacity of these compounds to activate defense mechanisms of Brazilian tomato varieties and other crops is important for exploring new and more sustainable strategies for pest management. 69,70 Another application derived from this study would be exploration of the two-in-one function that M. basicornis exhibited. Plant vaccination 43,71 by the mirid (i.e.…”