Abstract
Although the cultivation of transgenic plants expressing toxins of Bacillus thuringiensis (Bt) represents a successful pest management strategy, the rapid evolution of resistance to Bt plants in several lepidopteran pests has threatened the sustainability of this practice. By exhibiting a favorable safety profile and allowing integration with pest management initiatives, plant essential oils have become relevant pest control alternatives. Here, we assessed the potential of essential oils extracted from a Neotropical plant, Siparuna guianensis Aublet, for improving the control and resistance management of key lepidopteran pests (i.e., Spodoptera frugiperda and Anticarsia gemmatalis). The essential oil exhibited high toxicity against both lepidopteran pest species (including an S. frugiperda strain resistant to Cry1A.105 and Cry2Ab Bt toxins). This high insecticidal activity was associated with necrotic and apoptotic effects revealed by in vitro assays with lepidopteran (but not human) cell lines. Furthermore, deficits in reproduction (e.g., egg-laying deterrence and decreased egg viability), larval development (e.g., feeding inhibition) and locomotion (e.g., individual and grouped larvae walking activities) were recorded for lepidopterans sublethally exposed to the essential oil. Thus, by similarly and efficiently controlling lepidopteran strains susceptible and resistant to Bt toxins, the S. guianensis essential oil represents a promising management tool against key lepidopteran pests.
Highlights
The worldwide adoption of genetically modified crop plants expressing toxic proteins of the bacterium Bacillus thuringiensis (i.e., Bt toxins) was a response to the economic losses caused by lepidopteran pest species, in maize and soybeans[1]
The two major components of S. guianensis essential oils were the monoterpene β-myrcene (69.3–79.7%) and the ketone 2-undecanone (8.37–10.8%) (Table 1), there was a wide range of other compounds in smaller amounts in all of the three samples evaluated (Table 1)
We report on the high toxicity of the essential oil of a Neotropical plant, the Negramina S. guianensis, to the larval stages of key lepidopteran pests (i.e., A. gemmatalis and S. frugiperda, including a S. frugiperda strain that is resistant to the Cry1A.105 and Cry2Ab Bt toxins)
Summary
The worldwide adoption of genetically modified crop plants expressing toxic proteins of the bacterium Bacillus thuringiensis (i.e., Bt toxins) was a response to the economic losses caused by lepidopteran pest species, in maize and soybeans[1]. Recent studies described field-evolved Bt-resistance in the fall armyworm Spodoptera frugiperda to non-pyramided Bt plants expressing Cry1F, Cry1A. (Siparunaceae), commonly referred to as Negramina, ant bush or Capitiú, is a relevant example This plant species is widespread in South America, including the Brazilian Northeast and Mid-Western regions[20], and products derived from its leaves, bark, and flowers have been used in folk medicine[21,22,23]. The chemical constituents of essential oils of S. guianensis were initially identified and subsequently tested on the velvetbean caterpillar Anticarsia gemmatalis (Hübner), a key soybean pest species, and on Bt-susceptible and resistant strains of the fall armyworm Spodoptera frugiperda (J.E. Smith), a key pest species of maize and soybeans. We assessed the toxicity of this essential oil on lepidopteran and human cell lines
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