S23 - Session O5 - Encapsulation of dsRNA within nano-clay sheets reduces Botrytis cinerea colonization and gray-mold in harvested fruits

Authors: Danielle Duanis-Assaf, Ortal Galsurker, Ilya Shlar, Dalia Maurer, Oleg Feygenberg, Elena Poverenov, Robert Fluhr, Noam Alkan *

Postharvest loss is estimated at more than 40%. Pathogenic fungi cause a major part of this loss. The most effective treatment against postharvest diseases is fungicides. However, due to growing concern for their harmful influences, there is a need to develop new strategies to control postharvest pathogens. Botrytis cinerea , a common postharvest pathogen, infects over 200 plant species, causing grey-mold disease. Recently, it was demonstrated that B. cinerea can naturally uptakes double-stranded RNA (dsRNA) from the host plant and the environment. This dsRNA downregulates genes through the RNA interference system (RNAi). We developed dsRNA construct targeting three ergosterol biosynthesis essential genes, which compromise the fungal membrane biosynthesis. Due to the low stability of dsRNA, it was loaded onto layered double-hydroxide (LDH), which should protect the dsRNA from degradation and serve as a slow-release device. Our results show an initial uptake of dsRNA in the emergence zone of the conidia germination tube, leading to a reduction in fungal germination and growth both in-vitro and on various fruits including strawberries, mango, grapes, cherry, tomato, pepper, and more. The dsRNA exhibited systemic protection, decreasing decay development at inoculation points distant from the treatment point. All three target genes were down-regulated after dsRNA treatment, while addition of external ergosterol restored fungal growth, indicating RNAi activation. Furthermore, the LDH-dsRNA display an ability to serve as a selective treatment against B. cinerea and decreased gray-mold development while not affecting other fungi during storage. A prolonged effect was of the LDH-dsRNA complex decreased decay development in grapes that were infected five weeks after treatment. Moreover, storage conditions, as an increase in the CO­ 2 , affected the release pattern of the dsRNA from the LDH. Overall, this study suggests that dsRNA may serve as a future method of fungal control.