Differential Effects of Local dsRNA Application on Systemic Beet Mosaic Virus (BtMV) Resistance in Nicotiana benthamiana and Beta vulgaris.

Abstract

Beet mosaic virus (BtMV) is one of several viruses infecting sugar beets and was managed by controlling the vector Myzus persicae with neonicotinoid seed treatment. Following the ban of this measure in 2019 in Europe, alternative control strategies must be researched. One alternative might be the use of RNA interference (RNAi) as a major antiviral defence system. Here we report the selection of target regions using small RNA high throughput sequencing of BtMV infected Beta vulgaris subsp. vulgaris and Nicotiana benthamiana plants, the production of double-stranded RNA (dsRNA), and its effective use in inducing resistance against the mechanically inoculated virus. Both in Escherichia coli HT115 produced dsRNAs for BtMV P1 and nuclear inclusion body b (NIb) induced a high level of resistance, when sprayed before mechanical BtMV inoculation, resulting in an 80% reduction of symptomatic B. vulgaris and N. benthamiana plants. Stem-loop RT-qPCR showed the systemic distribution of dsRNA derived siRNA molecules, but the applied dsRNA remained at the site of application and did not spread within the plant. However, when the virus was inoculated on the next upward leaf to the dsRNA application site, no protective effect was observed. Despite this limitation, the results demonstrate the potential of dsRNA as an effective tool for viral protection in sugar beets, thereby establishing a basis for future developments in systemic delivery and broader field applications.