RNA interference: a promising biopesticide strategy against the African Sweetpotato Weevil Cylas brunneus

Abstract

The African sweetpotato weevil Cylas brunneus is one of the most devastating pests affecting the production of sweetpotatoes, an important staple food in Sub-Saharan Africa. Current available control methods against this coleopteran pest are limited. In this study, we analyzed the potential of RNA interference as a novel crop protection strategy against this insect pest. First, the C. brunneus transcriptome was sequenced and RNAi functionality was confirmed by successfully silencing the laccase2 gene. Next, 24 potential target genes were chosen, based on their critical role in vital biological processes. A first screening via injection of gene-specific dsRNAs showed that the dsRNAs were highly toxic for C. brunneus. Injected doses of 200ng/mg body weight led to mortality rates of 90% or higher for 14 of the 24 tested genes after 14 days. The three best performing dsRNAs, targeting prosα2, rps13 and the homolog of Diabrotica virgifera snf7, were then used in further feeding trials to investigate RNAi by oral delivery. Different concentrations of dsRNAs mixed with artificial diet were tested and concentrations as low as 1 μg dsRNA/ mL diet led to significant mortality rates higher than 50%.These results proved that dsRNAs targeting essential genes show great potential to control C. brunneus.

Delivery of gene‐specific dsRNA by microinjection and feeding induces RNAi response in Sri Lanka weevil, Myllocerus undecimpustulatus undatus Marshall

“…As observed in our study, suppression of Prosα2 and Snf7 transcript levels and significant mortality were reported in C. puncticollis and C. brunneus after oral delivery of dsRNA for the respective genes . In addition, we found that Snf7 dsRNA was the most lethal among the dsRNAs tested.…”

“…As observed in our study, suppression of Pros 2 and Snf7 transcript levels and significant mortality were reported in C. puncticollis and C. brunneus after oral delivery of dsRNA for the respective genes. 29,30 In addition, we found that Snf7 dsRNA was the most lethal among the dsRNAs tested. This result is in agreement with a number of studies that have shown high mortality in several insect species exposed to Snf7 dsRNA, including Diabrotica virgifera virgifera, 36 Diabrotica undecimpunctata howardi, 37 Halyomorpha halys 38 and Amrasca biguttula biguttula.…”

“…We demonstrated significant reduction in the transcript levels of all genes tested 3 days after dsRNA injection, suggesting that SLW adults possess a functional RNAi machinery and systemic RNAi response. Previous studies in weevils Cylas puncticollis and Cylas brunneus reported that injection of dsRNA for the same genes resulted in high lethality . Although gene expression was not evaluated in these previous works, the insect mortality was presumed to be due to gene knockdown.…”

“…Previous studies in weevils Cylas puncticollis and Cylas brunneus reported that injection of dsRNA for the same Pest Manag Sci 2020; 76: 936-943 genes resulted in high lethality. 29,30 Although gene expression was not evaluated in these previous works, the insect mortality was presumed to be due to gene knockdown. In experiments for gene functional analysis, the delivery of dsRNA is often performed by microinjection because a lower amount of dsRNA is required and the RNAi response is faster when compared to ingestion of dsRNA.…”

Implementing the sterile insect technique with RNA interference – a review

“…In this context, the development of new methods for insect control is of key importance and there has been intense interest in the utility of gene silencing methods induced by RNA interference (RNAi). RNAi can induce mortality (Yang & Han, ; Cao et al., ; Abd El Halim et al., ; Christiaens et al., ; Hu et al., ; Malik et al., ), create beneficial phenotypes for insect control (Salvemini et al., ; Shukla & Palli, ; Peng et al., ; Yu et al., ), and prevent pesticide resistance in insect pests (Figueira‐Mansur et al., ; Guo et al., ; Wei et al., ; Bona et al., ; Sandoval‐Mojica & Scharf, ). Therefore, the potential for RNAi as a basis for future pest management strategies holds great promise (Huvenne & Smagghe, ; Gu & Knipple, ; Scott et al., ; Baum & Roberts, ; Kim et al., ).…”