Abstract
Simple SummaryThe zoophytophagous mirid bug Nesidiocoris tenuis is an efficient predator of the tomato leafminer, Tuta absoluta. RNA interference (RNAi) targeting the alphaCOP (αCOP) (Coatomer subunit alpha protein) gene of N. tenuis (Nt-αCOP) was proven to be functional in N. tenuis, causing downregulation of gene expression, mortality and sub-lethal effects. In contrast, when N. tenuis were fed with dsRNA (dsTa-αCOP) targeting the ortholog αCOP gene of T. absoluta, no lethal nor sub-lethal effects were observed. These results indicate the compatibility of this biocontrol agent along with RNAi-mediated management in order to suppress T. absoluta efficiently in tomato crop.RNAi-mediated insect pest management has recently shown promising results against the most serious pest of tomato, the tomato leafminer, Tuta absoluta. This study aimed to investigate whether dsRNA (dsTa-αCOP) designed to target the T. absoluta-αCOP gene could cause adverse effects to its biocontrol agent, the mirid predator, Nesidiocoris tenuis. Oral exposure of N. tenuis to dsRNA (dsNt-αCOP) designed to target N. tenuis-αCOP resulted in a 61%, 67% and 55% reduction in its transcript level in comparison to the sucrose, dsGFP and dsTa-αCOP treatments, respectively. In addition, significantly higher mortality of 57% was recorded in dsNt-αCOP-treated N. tenuis when compared to the sucrose (7%), dsGFP (10%) and dsTa-αCOP (10%) treatments. Moreover, the predation rate of ~33–39 Ephestia kuehniella eggs per N. tenuis adult dramatically reduced to almost half in the surviving dsNt-αCOP-treated N. tenuis. This worst-case exposure scenario confirmed for the first time that the RNAi machinery is functional in this species and that the risk of exposure through the oral route is possible. In contrast, dsTa-αCOP did not cause any sub-lethal effects to N. tenuis upon oral exposure. Oral exposure of T. absoluta to dsTa-αCOP resulted in 50% mortality. In the context of a biosafety risk assessment of RNAi-mediated insect management, investigating the effects on non-target organisms is essential in order to include this method as part of an integrated pest management strategy. Based on our laboratory assays, RNAi-mediated control is compatible with the biological control of T. absoluta by its natural enemy N. tenuis, adding the RNAi approach in the armoire of integrated pest management of T. absoluta.
Highlights
The tomato (Lycopersicon esculentum) is one of the most important food and cash crops worldwide
DsRNA targeting the αCOP gene (Nt-αCOP) in N. tenuis was produced (Figure S1) and fed to N. tenuis nymphs. dsNt-αCOP-treated N. tenuis showed a mean reduction of Nt-αCOP transcript levels by 61% and 67% in comparison to the sucroseand the dsGFP-treated controls, respectively (Figure 2A)
This confirmed that the oral exposure of N. tenuis to gene-specific double-stranded RNA (dsRNA) can lead to RNAi-mediated gene knockdown
Summary
The tomato (Lycopersicon esculentum) is one of the most important food and cash crops worldwide. The voracious generalist predator Nesidiocoris tenuis (Reuter) (Hemiptera, Miridae) is a major biological control agent reported in tomato plants and is widely used against T. absoluta [3,4]. Apart from its beneficial role, N. tenuis may cause damage to the plant due to its phytophagy [8,9]. For this reason, the release of a lower number of N. tenuis is highly recommended [6]. The release of a lower number of N. tenuis is highly recommended [6] Another drawback of using N. tenuis is the need of extended establishment period on the crop [9]
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