Early Detection of the Seed-Borne Tobamoviruses Tomato Brown Rugose Fruit Virus and Tomato Mosaic Virus Using Portable Raman Spectroscopy

Tomato is one of the most widely cultivated vegetable crops because of its high nutritional value. However, its production is severely affected by numerous pathogens, including fungi, bacteria, phytoplasmas, viruses, and viroids. Among these, tomato mosaic virus (ToMV) and tomato brown rugose fruit virus (ToBRFV), both belonging to the genus Tobamovirus (family Virgaviridae), pose a major threat because of the exceptional stability of their virions and their persistence on seed coats. This feature facilitates seed-to-seedling transmission and contributes to virus spreading. The early detection of ToMV and ToBRFV using rapid, non-destructive, and cost-effective diagnostic techniques is essential for the sustainable production of certified planting material in tomato nurseries. Using a portable hand-held device, we investigated the potential of Raman spectroscopy (RS) to detect ToMV and ToBRFV infections in newly emerged tomato seedlings. To mimic natural seed-to-seedling transmission, seeds were artificially contaminated with purified ToMV or ToBRFV virions before sowing. Raman spectra were acquired from the first true leaf of each seedling, and following the identification of virus-infected plants by DAS-ELISA, the spectra of infected and healthy untreated control plants were compared. Virus infection was associated with significant reductions in the intensity of peaks assigned to carotenoids, aliphatic compounds, phenylpropanoids, pectin, lignin, and cellulose. These findings demonstrate the efficacy of a hand-held RS for the rapid, non-destructive and early detection of ToMV and ToBRFV infections in tomato seedlings, indicating that this approach has strong potential to support the production of certified planting material and improve disease management in nursery and production systems.