Tomato (Lycopersicon esculentum) plant showing symptoms attributed to geminivirus were collected from crops of the green belt of Campinas, SP. The symptoms consisted of leaf yellowing, especially along the veins, leaf distortion and reduced plant growth. A virus isolate was maintained in tomatoplants by whiteflies transmission at the Experimental Center of Instituto Agronômico in Campinas. Molecular tests were performed with the virus, which showed to be Tomato yellow vein streak virus (TYVSV). Evaluations of tomato resistance were done under field (natural infections) and screen house conditions (natural and controlled infections) using genotypes of diverse origins, comprising cultivars, hybrids, breeding lines, populations and wild tomato species. The evaluated material included experimental genotypes and hybrids carrying the gene for vertical resistance, Ty-1. In the field, the evaluations pointed to the hybrid 'BX 1016158' as having the the lowest disease infection rates. In screen house conditions, the interspecific hybrids of L. esculentum x L. peruvianum, and the access PI 134417 of L. hirsutum showed the highest resistance to the virus. Another screen house experiment used a method of early testing for resistance of tomato genotypes to geminivirus. This method proved to be adequate for discrimination of genotypes, found resistance in the L. peruvianum access LA 444-1, in the IAC 14-2 series, in the F4 line TySw5, and in the hybrids 'Franco' and BX 1653088 ('Densus'), with ratings close to absence of symptoms.
