Detection and phylogenetic analysis of saffron and tomato isolates of Tomato spotted wilt virus from South Khorasan

Tomato spotted wilt virus is a member of the genus Tospovirus, and family Bunyaviridae. TSWV has a wide range of hosts and is one of the most destructive viruses. In order to detect TSWV in South Khorasan province, a total of, 161 saffron and 44 tomato symptomatic samples were collected from Ghaen, Khosf, Darmyan and Ferdows counties, during fall 2016. Infection ratios on tomato and saffron were evaluated as 11.4 and 8.7 percent, respectively, by DAS-ELISA. Mechanical inoculation of ELISA-positive samples on Nicotiana benthamiana, N. tabacum cv Samsun and Chenopodium quinoa caused mosaic, mottle, local lesion and rogues. The nucleoprotein gene of five saffron and two potato isolates of TSWV was amplified, cloned, and sequenced. In the Phylogenetic tree based on nucleotide sequence of N protein gene, TSWV isolates dirived into three groups. Three Iranian isolates of saffron grouped into clusters one and three and two Iranian isolates of tomato were placed in group two. Results showed that isolates from different geographical and host plants were separated into different groups. According to our knowledge this is the first report on molecular characterization of TSWV on saffron in the world.