Molecular Characterization of Iranian isolates of Turnip mosaic virus –TuMV.

In the present work, natural hosts and distribution of Turnip mosaic virus-TuMV were investigated in 12 provinces. During the growing seasons 2002 to 2006, a total of 1655 random and 355 symptomatic samples were collected from various cruciferous cultural and ornamental plants as well as from non-cruciferous hosts, and their infection with TuMV was serologically tested by enzyme-linked immunosorbent assay (ELISA). The results were confirmed by host range and transmission studies. Base on the results obtained, TuMV should be considered as the most important cruciferous viruses in Iran. It was detected in 309 (24.5%) randomly collected samples. Furthermore, the virus was detected in all ornamental plants studied. Beside of cultural cruciferous plants, TuMV was detected in ornamental plants including Matthiola sp., Chiranthus cheiri, Chrysanthemum sp., Petunia hybrida, Impatient balsamina, Dahlia sp. and Zinia elegans. Also, natural infection of TuMV was detected in some brassica weeds, including Eruca sativa, Hirschfelida incana, Rapistrum rugosum and Sisymbrium irio and S. loeselii. This is the first report of these weeds as natural hosts for TuMV in Iran. In this study, biological diversity of 14 Iranian TuMV isolates was investigated for the first time using turnip and radish plants. The results showed that these isolates can be categorized to two biotypes of B and BR. Aphid transmission studied showed that all isolates tested are transmitted by Myzus persicae. For further molecular studies and to determine phylogenetic relationships of the Iranian TuMV isolates, the nucleotide sequence of coat protein (CP) and P1 genes for the 14 isolates, were determined and compared with 106 nucleotide sequences in GenBank. The phylogenetic tree was determined based on ML. The identities between 14 diferent Iranian isolates was 92/2-98/8% and most identities was determined between IRNES1 and IRNEB1 from Esfahan and the low indentites was belong to IRNKhCa and IRNRS2 from Khorasan and Fras respectively. Molecular studies showed that the Iranian isolates are clustered in three genogroups, including basal-B, Asian BR and an independent new group. This study shows for the first time the wide distribution and phylogenetic relationships of TuMV collected from different hosts in the mid-Eurasia of Iran. Based on the resultes it seemes that Iran (in mid-Eurasia) can be origin of this Virus. However, for determine the persition of phylogentic of Iranian isolates we need more information and complete sequence of Iranian and non-Iranian isolates of TuMV in mid-Eurasia. Keywords: Iran, Turnip mosaic virus, Brassicaceae, distribution, natural hosts, phylogeny