Detection of a novel tospovirus in chrysanthemum.

Up to 1994, tomato spotted wilt virus (TSWV) was the only tospovirus species reported in chrysanthemum (Dendranthema morifolium) in the Netherlands. Since then, however, occasionally an aberrant tospovirus was found in this ornamental. The virus evoked symptoms similar to those caused by TSWV, i.e. mild to severe stem necrosis, wilting of leaves and stems, and chlorotic and/or necrotic spots and rings on some of the leaves. The virus was isolated from different cultivars grown in different greenhouses. Test plants mechanically inoculated with this virus, produced symptoms that resemble those caused by TSWV. The most obvious differences were observed in Datura stramonium, in which only the tospovirus from chrysanthemum evoked stem necrosis and in Physalis floridana, in which systemic symptoms were caused by TSWV but not by the chrysanthemum virus. The symptoms produced on Citrullus lanatus ‘Dulzura’, Nicotiana occidentalis-P1 and Phaseolus vulgaris ‘Dubbele Witte zonder draad’ and ‘Pinto’ differ slightly from those caused by TSWV. Lycopersicum esculentum appeared to be less susceptible for this virus than for TSWV. Electron-microscopic studies revealed the presence of tospovirus-like particles in infected plants. In ELISA, however, the tospovirus from chrysanthemum did not react with antisera to the nucleocapsid protein of TSWV, neither to those of Impatiens necrotic spot virus, watermelon silver mottle virus and a tospovirus isolated from iris, respectively. Based on these results it is concluded that the tospovirus from chrysanthemum is a distinct virus that does not belong to any of the established serogroups. Sofar, in each greenhouse in which the first infection of this novel virus was found, chrysanthemum plants were derived from mother plants in Brazil, suggesting that the virus is endemic in South America.