Tomato is one of the economically important agricultural crops worldwide. Approximately 80% of tomatoes are consumed fresh, while 20% are used in various processed food products. The tomato production in the United States (US) contribute and $2.8 billion to the national economy annually. However, virus infections are a major threat to tomato production and fruit quality. Tomato brown rugose fruit virus (ToBRFV) which was reported in 2014 and has spread in more than 50 countries since then, is a highly infectious and stable Tobamovirus spreads mechanically and can stay on a surface for weeks. Its ability to overcome existing resistance genes in tomato is the main concern, emphasizing the urgent need to identify tolerance or resistance in tomatoes cultivars. Besides this, horse nettle virus A (HNVA), recently reported to infect tomatoes in Oklahoma was previously limited to a weed named horse nettle (Solanum carolinense), and exhibits a concerning host shift, causing symptoms such as curling, cupping, and brown discoloration of leaves in tomatoes plants. The objective of this study was to evaluate commercially cultivated tomato cultivars in the US for resistance against both ToBRFV and HNVA. The tomato seedlings were inoculated mechanically with ToBRFV and HNVA and were observed and scored weekly at 7-, 14-, 21-, and 28-days post-inoculation (dpi) on a severity scale of 0 to 3 where 0,1, 2, and 3 correspond to no symptoms, mild, mildly severe and severe symptoms respectively. At 28 dpi, representative plants were tested using virus-specific RT-PCR assays to confirm systemic infection. The findings suggest that there are no resistant cultivars against ToBRFV while there are some showing tolerance based on the symptom severity scores. For HNVA, 22 cultivars have been screened so far and were mostly tolerant but not resistant. These results provide insights into the interaction of these emerging viruses with widely grown tomato cultivars and help us to identify tolerant cultivars to inform the growers and the variation in disease severity which would be valuable for breeders to guide future breeding strategies aimed at ToBRFV and HNVA resistance.
