First Evidence of Bud Feeding-Induced RNAi in a Crop Pest via Exogenous Application of dsRNA.

Jonathan Willow,Silva Sulg,Olivier Christiaens,Guy Smagghe,Ana Isabel Silva,Riina Kaasik,Clauvis Nji Tizi Taning,Liina Soonvald,Eve Veromann

doi:10.3390/insects11110769

Jonathan Willow, Silva Sulg + Show 7 more

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https://doi.org/10.3390/insects11110769

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Abstract

Simple SummaryAn ecologically sustainable strategy for managing the pollen beetle Brassicogethes aeneus, a key pest of oilseed rape (Brassica napus) in Europe, is greatly needed. Gene silencing via RNA interference, through sprayed applications of target-specific double-stranded RNA, represents a potential alternative to conventional insecticides. We used dsRNA designed to target a vital gene in this pollen beetle species and allowed the beetles to feed on dsRNA-coated oilseed rape buds. We observed a significant silencing of the target gene; and this was followed by a significant, albeit delayed, reduction in pollen beetle survival rate. Further experiments are necessary in order to better understand the potential for developing a dsRNA-spray approach to pollen beetle management.Spray-induced gene silencing (SIGS) is a potential strategy for agricultural pest management, whereby nucleotide sequence-specific double-stranded RNA (dsRNA) can be sprayed onto a crop; the desired effect being a consumption of dsRNA by the target pest, and subsequent gene silencing-induced mortality. Nucleotide sequence-specificity is the basis for dsRNA’s perceived biosafety. A biosafe approach to pollen beetle (Brassicogethes aeneus) management in oilseed rape (Brassica napus) agroecosystems is needed. We examined the potential for SIGS in B. aeneus, via bud feeding, a field-relevant dsRNA exposure route. Oilseed rape buds were uniformly treated with dsRNA designed to target αCOP in B. aeneus. Our model control dsRNA (dsGFP) remained detectable on buds throughout the entire 3 d exposure period. When applied at 5 µg/µL, dsαCOP induced significant αCOP silencing 3 d after dietary exposure to buds treated with this dsαCOP concentration. We also observed a trend of increased αCOP silencing with increasing concentrations of dsαCOP at both 3 and 6 d. Furthermore, we observed a marginally significant and significant reduction in B. aeneus survival at 10 and 15 d, respectively. Our results suggest potential for developing a SIGS approach to B. aeneus management—though further experiments are needed to more fully understand this potential.

Highlights

In the insects that fed upon the buds, our obtained quantitative polymerase chain reaction (qPCR) results showed a trend of reduced αCOP expression, with an increasing concentration of dsαCOP application, at both 3 and 6 d (Figure 2)
We provide laboratory evidence suggesting some potential for incorporating a Spray-induced gene silencing (SIGS) approach in survival at 10 and 15 d, respectively, as well as a trend of lower relative expression of αCOP with within integrated B. aeneus management
We observed marginally significant and significant increasing concentrations of dsαCOP, indicating that the mortality observed in our B. aeneus RNA interference (RNAi) reductions in survival at 10 and 15 d, respectively, as well as a trend of lower relative expression of assays were a result of silencing the target gene αCOP

Summary

Introduction

Meligethes aeneus) is a key pest of oilseed rape (Brassica napus L.) in Europe. Adult B. aeneus overwinter in soil, under vegetation and leaf litter; they emerge in early spring to feed on the pollen and nectar of a variety of blooming plants, and subsequently colonize brassicaceous plants, where they obtain nutrients from reproductive buds and open flowers. Oilseed rape crops are most susceptible to B. aeneus during the green bud stage. Model predictions demonstrate that the extensive bud feeding by B. aeneus can result in great economic losses, depending on different factors such as the number of pollen beetles and immigration time [2,3]. Current B. aeneus control measures usually occur via the application of synthetic agrochemicals, for example the neonicotinoid insecticide thiacloprid [4,5]. These, have shown detrimental effects on nontarget organisms, including hymenopteran parasitoids [6,7,8], a functional group of critical importance for the biocontrol of B. aeneus populations [9,10]

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