dsRNA-Mediated Pest Management of Tuta absoluta Is Compatible with Its Biological Control Agent Nesidiocoris tenuis

Simple Summary: The zoophytophagous mirid bug Nesidiocoris tenuis is an efficient predator of the tomato leafminer, Tuta absoluta. RNA interference (RNAi) targeting the alphaCOP (alpha COP) (Coatomer subunit alpha protein) gene of N. tenuis (Nt-alpha COP) 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-alpha COP) targeting the ortholog alpha COP 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-alpha COP) designed to target the T. absoluta-alpha COP gene could cause adverse effects to its biocontrol agent, the mirid predator, Nesidiocoris tenuis. Oral exposure of N. tenuis to dsRNA (dsNt-alpha COP) designed to target N. tenuis-alpha COP resulted in a 61%, 67% and 55% reduction in its transcript level in comparison to the sucrose, dsGFP and dsTa-alpha COP treatments, respectively. In addition, significantly higher mortality of 57% was recorded in dsNt-alpha COP-treated N. tenuis when compared to the sucrose (7%), dsGFP (10%) and dsTa-alpha COP (10%) treatments. Moreover, the predation rate of similar to 33-39 Ephestia kuehniella eggs per N. tenuis adult dramatically reduced to almost half in the surviving dsNt-alpha COP-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-alpha COP did not cause any sub-lethal effects to N. tenuis upon oral exposure. Oral exposure of T. absoluta to dsTa-alpha COP 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.

Automated summary

The zoophytophagous mirid bug Nesidiocoris tenuis is an efficient predator of the tomato leafminer, Tuta absoluta. RNA interference targeting the alpha COP gene of N. tenuis showed functional effects, but no significant adverse effects were observed when N. tenuis were exposed to dsRNA targeting the ortholog alpha COP gene of T. absoluta.