Response of Local Tomato Ecotypes from the Campania Region (Italy) to Infections by Potato virus Y (C-to strain) and Potato Spindle Tuber Viroid.

Tomato (Solanum lycopersicum) is one of the most important solanaceous crops due to its economic and nutritional relevance. However, it is susceptible to a wide range of plant pathogens, including a recombinant strain of potato virus Y (PVYC-to) and potato spindle tuber viroid (PSTVd), both of which are considered major threats to tomato cultivation. PVYC-to, a singlestranded RNA virus (family Potyviridae), induces symptoms such mosaic, chlorosis, and vein necrosis in horticultural crops, leading to significant production losses. PSTVd, a nuclear- replicating viroid (family Pospiviroidae), elicits stunting and leaf curling in tomato plants. This study aimed to assess the susceptibility of five local tomato ecotypes from the Campania region (Corbarino, Vesuviano, Giallo determinato da Serbo, Pizzutello, and San Marzano) to PVYC-to and PSTVd infections. Visual symptom assessment at 14 and 28 days postinoculation (dpi) and quantification of virus and viroid accumulation using qDot-Blot or RT-qPCR showed that all ecotypes were susceptible to PVYC-to and PSTVd infections, although the severity of symptoms and the accumulation level of the virus/viroid in the infected tissues was differed depending on the ecotype. Notably, Corbarino and San Marzano showed mild symptoms and reduced pathogen accumulation upon PVYC-to and PSTVd infection, respectively, revealing a certain level of tolerance. In contrast, the ecotypes Giallo determinato da serbo and San Marzano were particularly susceptible to PSTVd and PVYC-to, respectively. The local tomato ecotypes identified in this study may serve as valuable resources to further explore the molecular pathways underlying tomato defence responses against PVYC-to and PSTVd infections.