Tomato fruit blotch virus: an update on epidemiology, cytopathology and molecular features.

Tomato fruit blotch virus (ToFBV, genus Blunervirus, family Kitaviridae) is the proposed name for a newly identified virus that causes uneven and blotchy ripening along with dimpling and dark spots on tomato (Solanum lycopersicum L.) fruits. From its first identification in 2018-2019 in Italy and Australia (Ciuffo et al., 2020), it was newly reported in Spain (Maachi et al., 2021), Brazil (Nakasu et al., 2022), Slovenia (Rivarez et al., 2022) and Tunisia (TC, ABH and MC, unpublished), and retrieved from stored samples, dating back its presence in Italy to 2012 (Ciuffo et al., 2020). Bacilliform particles in blotched areas on pericarp of infected tomato fruits, accumulating in the perinuclear space and lumen of the endoplasmatic reiticulum, were observed by TEM (Kitajima et al., 2022). Further studies on ToFBV biology and epidemiology are being conducted to allow a preliminary assessment of its phytosanitary risk. Our data suggest that ToFBV infects the plants with a variable titer in fruit tissues, with pericarp showing a higher virus concentration than placenta and endocarp. Seeds are only contaminated on their external tegument, but the virus appears unable to replicate in the emerging seedlings, thus excluding its seed transmissibility. A likely candidate vector for ToFBV is the tomato russet mite (Aculops lycopersici Massee, family Eriophyidae) and transmission trials are in progress. Insights on the distribution and characteristics of this virus expanded through prepublication data sharing involving international collaboration across 12 organisations from nine countries, from Africa, Europe, Oceania and South America.