Search

BACKGROUND: Double‐stranded RNA (dsRNA) biopesticides are of interest for the abatement of insect vectors of pathogenic bacteria such as 'Candidatus Liberibacter', which infects both its psyllid and plant hosts. Silencing of genes essential for psyllids, or for Liberibacter, is anticipated to lead to mortality or impeded bacterial multiplication. Foliar delivery is preferred for biopesticide application; however, the cuticle impedes dsRNA penetration into the vasculature. Here, conditions were established for wounding tomato leaves using ultraviolet light amplification by stimulated emissions of radiation (UV‐LASER) to promote dsRNA penetration into leaves and vasculature. RESULTS: UV‐LASER treatment with application of select adjuvants/surfactants resulted in vascular delivery of 100‐, 300‐ and 600‐bp dsRNAs that, in general, were correlated with size. The 100‐bp dsRNA required no pretreatment, whereas 300‐ and 600‐bp dsRNAs entered the vasculature after UV‐LASER treatment only and UV‐LASER adjuvant/surfactant treatment, respectively. Of six adjuvant/surfactants evaluated, plant‐derived oil combined with an anionic organosilicon compound performed most optimally. Localization of dsRNAs in the tomato vasculature was documented using fluorometry and fluorescence confocal microscopy. The biological activity of in planta‐delivered dsRNA (200–250 bp) was determined by feeding third‐instar psyllids on tomato leaves post UV‐LASER adjuvant/surfactant treatment, with or without psyllid cdc42‐ and gelsolin dsRNAs. Gene knockdown was quantified by quantitative, real‐time polymerase chain reaction with reverse transcription (RT–qPCR) amplification. At 10 days post the ingestion‐access period, knockdown of cdc42 and gelsolin expression was 61% and 56%, respectively, indicating that the dsRNAs delivered to the tomato vasculature were mobile and biologically active. CONCLUSION: Results indicated that UV‐LASER adjuvant/surfactant treatments facilitated the delivery of mobile, biologically active dsRNA molecules to the plant vasculature. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

RNAi promises to reshape pest control by being nontoxic, biodegradable, and species specific. However, due to the plastic nature of RNAi, there is a significant variability in responses. In this study, we investigate small RNA pathways and processing of ingested RNAi trigger molecules in a hemipteran plant pest, the whitefly Bemisia tabaci Unlike Drosophila , where the paradigm for insect RNAi technology was established, whitefly has abundant somatic piwi-associated RNAs (piRNAs). Long regarded as germline restricted, piRNAs are common in the soma of many invertebrates. We sought to exploit this for a novel gene silencing approach. The main principle of piRNA biogenesis is the recruitment of target RNA fragments into the pathway. As such, we designed synthetic RNAs to possess complementarity to the loci we annotated. Following feeding of these exogenous piRNA triggers knockdown as effective as conventional siRNA-only approaches was observed. These results demonstrate a new approach for RNAi technology that could be applicable to dsRNA-recalcitrant pest species and could be fundamental to realizing insecticidal RNAi against pests., (© 2020 Mondal et al.)