New and emerging Tospovirus diseases

Tospoviruses cause severe diseases in many crops all over the world. We will report on the identification and characterization of a number of putative new species from the Americas, Asia and Europe. A new lineage of Tospoviruses was established including Bean necrotic mosaic virus and Soybean vein necrosis-associated virus isolated in Brasil and USA respectively; Pepper necrotic spot virus is present in solanaceous hosts in Peru; Alstroemeria necrotic streak virus was isolated in 2010 in Colombia. Melon severe mosaic virus was also a recently characterized tospovirus species widespread on melon crops in Mexico. In Asia, Tomato necrotic ringspot virus from Thailand and Tomato zonate spot virus from China were respectively identified in 2011 and 2010. The tospovirus Polygonum ringspot virus (PolRSV), the only new species isolated in Europe, will be subject of specific attention because it was isolated from a common weed and because of the specificity of its vector, Dictyothrips betae, a new vector species for tospoviruses. Furthermore this virus has two interesting molecular features that are absent in other Tospoviruses: the small segment intergenic region displays a short stretch of AT reach repeats, with no possibility of internal pairing, as it is usually the case with all the other tospovirus species, implying a different mechanism for subgenomic transcription. Furthermore, an unreported RNA species resulting from the dimerization the S segment with a small deletion of circa 300 nt at the 5' end of the second RNA molecule accumulates during PolRSV infection of Nicotiana benthamiana and N. clevelandii.