First report in Spain of a variant of Tomato mosaic virus (ToMV) overcoming the Tm-22 resistance gene in tomato (Lycopersicon esculentum).
A naturally infected tomato plant showing stunting and necrosis in the apical leaves was tested for viruses by ELISA using polyclonal antisera and was found positive for tobacco mosaic virus (TMV) and tomato mosaic virus (ToMV). A product of the expected size (419 nt) was amplified from nucleic acid extracts obtained from infected tomato (cv. Marmande) by RT-PCR using the ToMV-specific primers 1F and 1R. The sequence analysis showed 99.63% homology with ToMV strain L11A, which is able to overcome the resistance conferred by the tomato Tm-22 gene. No amplicons were produced using TMV-specific primers. This is thought to be the first report from Spain of a ToMV variant that overcomes the Tm-22 resistance gene in tomato.