بررسی تنوع و تکامل ویروس موزاییک رگه ای گندم در منطقه هلال حاصلخیز

Wheat streak mosaic virus (WSMV) is one of the most important viruses in the major wheat growing regions in the world. Molecular studies provide a new window to the understanding of the identification of WSMV strains and its diversity and evolution. This is necessary for understanding of epidemiology and management of the disease. In this project, thirty one isolates of (WSMV) from different regions of Iran were collected, sequenced and analyzed. In phylogenetic studies, all isolates of WSMV, excluding divergent Behbahan and EI Batan isolates can be assigned to two major branches (lineages), I and II, Branch I is designated as Fertile Crescent (FC). The second branch (lineages) comprises further divided into two lineages: (1) Iranian Plateau (IP) and (2) Eurasia. In spite of, widely distribution of Western Atlantic Lineage (W AL) in American continent and Australia, it seems that, it has changed very slowly and does not have a very long history in the New World, and its population has reached a genetic stability with low diversity. In contrast, high diversity in the Iranian populations indicates long precedence of evolution in Iran. Based on the present information, the Fertile Crescent in which wheat was originated, is the epicenter ofWSMV. The phylogenetic diversity is congruent with biogeographic distribution of WSMV populations. These populations have diverged into two large branches during evolutionary history. One branch is the Fertile Crescent (FC) populations which have moved to American and Australian continents. The second branch was further divided into two subbranches. One of them has transferred to Europe and Russia (Eurasia) and the other has moved to the central part of Iranian Plateau (IP) and has been further subdivided and distributed in other parts of Iranian Plateau (Fars, Khorasan, Zanjan, Kurdistan and Khuzistan provinces). The above analyses showed that the two diverged isolates, Behbahan from Iran, and EI Batan 3 from Mexico, despite having parallel evolutionary course are originated from distinct lineages. The Behbahan isolate has been originally derived from isolates of central part of Iran. The EI Batan 3 isolate, on the other hand, appears to have originated from FC lineage. This indicates that WSMV has crossed Atlantic Ocean more than once. Although, these two isolates were originated from two different lineages, they show high rate of evolution, and it is probable that geographical conditions have affected their evolution. Keywords: Wheat streak mosaic virus, coat protein, Tritimovirus, evolution, Fertile Crescent, Iranian Plateau