In the current proposal, we aim to investigate the potential of RNA sprays to protect and improve tomato, one of the most widely cultivated food crops in the world. Through RNA sprays that will trigger RNA interference (RNAi) by methods previously developed by the fellow 1, 2, we will aim to combat some of tomato's most severe and diverse natural enemies such as: (1) Cucumber mosaic virus (CMV), which infects tomato and produces symptoms such as shoestring-like leaf blades and results in significant yield losses 3. (2) Potato spindle tuber viroid (PSTVd), a non-coding and non-encapsidated RNA molecule that severely affects tomato plants, causing yellowing of the leaves, shortening of the internodes and flower abortion, leading to almost 60% yield loss 4. (3) Sorghum halepense, a weed largelyresistant to herbicides, growing and spreading so quickly that chock out tomato plants, reducing fruit size, weight and overall yield 5. Besides targeting plant enemies, we will also target plant benefactors, such as (4) Fusarium solani (strain FsK), and endophytic fungus which grows in root cortex and is shown to stimulate plant growth and confer resistance against pathogenic fungi and insects 6, 7. Importantly, and in order to unravel the molecular mechanisms of this fungus’ beneficial impact on the plant, the bi-directional trafficking between F. solani FsK and plant will be investigated.
1. Dalakouras, A. et al. Delivery of hairpin RNAs and small RNAs into woody and herbaceous plants by trunk injection and petiole absorption. Front Plant Sci 9, 1253 (2018).
2. Dalakouras, A. et al. Induction of Silencing in Plants by High-Pressure Spraying of In vitro-Synthesized Small RNAs. Front Plant Sci 7, 1327 (2016).
3. Gottula, J. & Fuchs, M. Toward a quarter century of pathogen-derived resistance and practical approaches to plant virus disease control. Adv Virus Res 75, 161-183 (2009).
4. Owens, R.A. & Hammond, R.W. Viroid pathogenicity: one process, many faces. Viruses 1, 298-316 (2009).
5. Ikley, J., Wise, K. & Johnson, G. Annual Ryegrass (Lolium multiflorum), Johnsongrass (Sorghum halepense), and Large Crabgrass (Digitaria sanguinalis) are Alternative Hosts for Clavibacter michiganensis subsp. nebraskensis, Causal Agent of Goss's Wilt of Corn. Weed Science 63(4), 901-909 (2015).
6. Kavroulakis, N. et al. Role of ethylene in the protection of tomato plants against soil-borne fungal pathogens conferred by an endophytic Fusarium solani strain. J Exp Bot 58, 3853-3864 (2007).
7. Pappas, M.L. et al. The Beneficial Endophytic Fungus Fusarium solani Strain K Alters Tomato Responses Against Spider Mites to the Benefit of the Plant. Front Plant Sci 9, 1603 (2018).