Tomato spotted wilt virus:: Causal agent of wilt in "miguelito" (Zinnia elegans Jacquin) in Morelos, Mexico

Mottle symptoms, necrotic ring spots, dwarfism, and severe wilt were observed on "miguelito" (Zinnia elegans Jacquin) (Fam: Comositae) plants cultivated in commercial nurseries in the State of Morelos, Mexico. Therefore, this study was conducted to determine the etiology of the disease. Tomato spotted wilt virus (TSWV) was identified as the causal agent of the disease in miguelito by mechanical transmission tests on indicator plants and pathogenicity tests on healthy Z. elegans seedlings cultivated from seed in a greenhouse. On these plants the virus caused mottled symptoms, necrotic spots in the form of concentric rings, dwarfism and wilt, identical to those observed in miguelito plants cultivated in field conditions. Through serology (DAS-ELISA) only TSWV was detected in miguelito plants with wilt symptoms from commercial nurseries in the State of Morelos, in indicator plants used to separate the virus, and in miguelito plants produced from seed and inoculated with a pure isolate of TSWV in the greenhouse. Taxonomical identity of TSWV was confirmed by direct sequencing of the RT-PCR products. The TSWV sequences obtained from field samples of miguelito (access number EF067862) and the same virus separated from N. rustica (access number EF067863) showed 100% homology in the amplified fragment of the capsid protein gene of TSWV, while with the samples of TSWV isolates widely distributed over the world existing in the INCBI/GeneBank there was 93% homology. This paper is the first report of the presence of TSWV in Z. elegans in Mexico, and two molecular methods for diagnosing and identifying this virus are described.