Molecular and biological characterization of an isolate of Tomato mottle mosaic virus (ToMMV) infecting tomato and other experimental hosts in eastern Spain

Tomato is known to be a natural and experimental reservoir host for many plant viruses. In the last few years a new tobamovirus species, Tomato mottle mosaic virus (ToMMV), has been described infecting tomato and pepper plants in several countries worldwide. Upon observation of symptoms in tomato plants growing in a greenhouse in Valencia, Spain, we aimed to ascertain the etiology of the disease. Using standard molecular techniques, we first detected a positive sense single-stranded RNA virus as the probable causal agent. Next, we amplified and sequenced its full-length genomic RNA which identified the virus as a new ToMMV isolate. Through extensive assays on distinct plant species, we investigated the host range of the Spanish ToMMV isolate. Several plant species were locally and/or systemically infected by the virus, some of which had not been previously reported as ToMMV hosts despite they are commonly used in research greenhouses. Finally, two reliable molecular diagnostic techniques were developed and used to assess the presence of ToMMV. This is the first observation of ToMMV in tomato plants in Europe. We discuss the possibility that, given the high sequence homology between ToMMV and Tomato mosaic virus , the former may have been mistakenly diagnosed as the latter by serological methods.