Spray application of BcBmp3-dsRNA delivered by layered double hydroxide (LDH) clay nanosheets reduces virulence of Botrytis cinerea on Lactuca sativa: first results.

Recently novel strategies based on the use of RNA interference (RNAi) are rising up in the crop protection scenario. Spray-induced gene silencing (SIGS) is a potential strategy for plant disease management, whereby nucleotide sequence-specific double-stranded RNA (dsRNA) can be sprayed onto a crop and it could represent a potential alternative to conventional fungicides. SIGS could give rise to transient silencing without producing genetically modified organisms (GMO) neither requiring transformation method for plants. Nevertheless, the instability of naked dsRNA sprayed on plants is a major challenge towards its practical application. To overcome this limiting aspect, nanocarriers for dsRNA delivery can be used to extend its stability and durability. We previously shown that topical application of a BcBmp3-dsRNA construct mediated both in vitro and in vivo knockdown of B. cinerea transcripts on Lactuca sativa. Our dsRNA construct was loaded on non-toxic, degradable, layered double hydroxide clay nanosheets for a sustained release on the leaf surface under ambient conditions. We prepared LDH by a modified non-aqueous method and the BcBmp3-dsRNA/LDH optimal ratio was assessed by the gel retardation assay. Lettuce plants were sprayed with either water, LDH, or BcBmp3-dsRNA/LDH complex on day 0. B. cinerea was inoculated using a conidial suspension 7 days after spray treatment. A significant reduction of gray mould severity was observed as assessed by a rating scale and by calculating the McKinney index. Our results suggest a possible development of SIGS approach for the management of B. cinerea disease, although further experiments are needed to fully understand this potential.