Reticine A, a new potent natural elicitor: isolation from the fruit peel of Citrus reticulate and induction of systemic resistance against tobacco mosaic virus and other plant fungal diseases

Background: Systemic acquired resistance (SAR) induced by elicitors is a highly satisfying form of resistance that protects plants against invading pathogens. Exploration and development of new elicitors is a promising alternative to conventional biocides in resistant pest management. In our previous broad screening, the fruit peel extract of Citrus reticulata Blanco exhibited the ability to induce SAR in tobacco.

Result: A new potent elicitor reticine A was isolated from the fruit peel extract of industrial crop C. reticulate and its structure was well elucidated. In vivo assays showed that reticine A had considerable control efficacies at 100 μg/mL and 500 μg/mL, being superior to commercial elicitor benzothiadiazole (BTH) (100 μg/mL). Reticine A had no significant impacts on the virulence of TMV particles under in vitro condition. Application of reticine A induced the local hypersensitive reaction (HR), the systemic accumulation of H₂ O₂ and salicylic acid (SA), the systemic increase of defensive enzyme activities and the systemic up-regulated expression of pathogenesis-related (PR) proteins, suggesting its induction of SAR in tobacco. The expression of NPR1 and SA biosynthesis genes ICS and PAL was systemically up-regulated.

Conclusion: The SAR induced by reticine A against TMV in tobacco was demonstrated and the mechanism might be attributed to activating the expression of several defensive genes mediated by SA signal. This study highlights the potential of reticine A that is recommended to be applied directly or as an active ingredient in the crude extract formulation ahead of time in the field, as well as being a potential lead compound for further optimization. This article is protected by copyright. All rights reserved.

Keywords: Citrus reticulate peel; reticine A; systemic acquired resistance.