Danielle Duanis-Assaf
Ilya Shlar
Ortal Galsurker
Olga Davydov
Dalia Maurer
Oleg Feygenberg
Elena Poverenov
Robert Fluhr
Noam Alkan
Major losses in postharvest fruit and vegetables are due to rotting caused by pathogenic fungi. The environmental impact of fungicides requires new eco-friendly strategies to control postharvest pathogens. B. cinerea, a major postharvest pathogen, was controlled by dsRNA targeting three key genes in ergosterol biosynthesis. However, due to the limited stability of dsRNA, we incorporated the dsRNA in layered-double hydroxide (LDH) nano-clays to protect the dsRNA from degradation and serve as a long-term controlled-release mechanism. Our results show that either in-vitro and in-planta, the hyphae and conidia emergence zone of the germination tube of B. cinerea can uptake free dsRNA or when it was complexed with LDH. The fungal inhibition provided by either form of dsRNA was selective to B. cinerea and not for other pathogens. Notably, the LDH-dsRNA complex maintained its potency for at least six weeks of cold storage and reduced gray mold development significantly better when compared to naked dsRNA after long storage. Scanning electron microscopy images implies that LDH by itself forms a mechanical barrier and delays the fungal colonization in the fruit. Furthermore, a modified atmosphere can influence the release of the dsRNA from the LDH complex. Thus, increased levels of CO2 and humidity increase LDH degradation, and the dsRNA release from the complex. Overall, our results suggest that the incorporation of dsRNA in LDH under suitable conditions may serve as a safe alternative to the postharvest application of fungicides.
