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RNA interference (RNAi) is a mechanism in which dsRNA is processed by the cell machinery mediating post-transcriptional or transcriptional gene silencing. RNAi is known to occur in all four eukaryotic kingdoms and, over the last 30 years, has been successfully used as a strategy for protecting transgenic plants against viral pathogens. Currently, novel approaches using topically applied dsRNA against plant viruses are under development. Despite several research groups reporting promising results under laboratory conditions, several factors, such as cost of production, lack of adequate product formulation, and short lifespan, hamper the development of this technology for commercial use. This review presents an up-to-date panorama on the advances of this strategy for crop protection against viruses and the major constraints for its development.

Sweetpotato (Ipomoea batatas(L.) Lam.) is a highly nutritious food crop that suffers severe yield losses due to viral diseases. These are unintentionally spread mainly by vegetative propagation techniques commonly used by farmers. Virus indexing of vine cuttings (slips) coupled with tools specifically developed for identification of the main viruses is therefore essential to avoid disease outbreaks. In this work, we assessed the viral diversity in sweetpotatoes collected in some of the main producing areas in Brazil. The cuttings were grafted onto Ipomoea setosaKer Gawl. prior to being subjected to ELISA for ten different viruses. Total DNA and RNA were also extracted from sweetpotato and I. setosaleaves for high-throughput sequencing (HTS) on an Illumina platform. Using this HTS strategy, nine viral species known to infect sweetpotatoes were identified, being seven of those species also identified in grafted I. setosa, two species identified exclusively in sweetpotato and two exclusively on I. setosa. From the ten different viruses tested by ELISA, six were identified in the samples evaluated. The generated data will be useful for virus indexing of sweetpotato as well as for virus resistance screening in sweetpotato breeding programs.

Two Bemisia tabaci(Gennadius) species, Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED), are major pests that are dispersed throughout the world. While MEAM1 was introduced in Brazil in the 1990s, MED was reported recently with limited spread. Here, a survey was performed to examine whether MED whiteflies are widely present in the Federal District region, in central Brazil. Whiteflies were collected in various locations in the Federal District and surroundings between 2018 and 2020, including garden centers and small- and large-scale farms. The species were identified using RFLPand sequencing of the mitochondrial cytochrome c oxidase Isubunit gene region. Out of 108 whitefly batches, 63.89% were composed exclusively by MEAM1, followed by 16.67% presenting only MED, and another 7.40% containing unidentified whitefly species (NI). Plant varieties serving as hosts for more than one whitefly species were observed in 12.04% of the samples, either by MEAM1/MED, MEAM1/NI, or MED/NI. This study highlights the still limited presence of MED in the Federal District and surroundings, predominantly in garden centers and in the green belt of Brasília, closer to urban areas. In contrast, only MEAM1 was identified in large-scale cultivated areas.