Phylogenetics and evolution of wheat streak mosaic virus: Its global origin and the source of the Australian epidemic

Wheat streak mosaic tritimovirus (WSMV) seriously damages wheat worldwide. We report analyses of new complete ORF (CO) sequences from seven Australian isolates with 56 COs and 128 coat protein (CP) genes sequenced previously. Eleven CO three CP were recombinants so removed our analyses. Patristic distances maximum-likelihood phylogenies nonrecombinant (n-rec) their closely correlated (R = 0.994, p ≤ 0.00001). The phylogeny all 188 n-rec had four well-supported phylogroups (I–IV): phylogroup I (one Mexican sequence), II (six Iranian sequences), III (48 sequences) IV (133 each basal either mostly European (phylogroup III) or American IV) terminal sequences. South formed a subcluster within Pacific Northwest USA cluster. Unlike the Iranian, populations, North populations demonstrated recent population imbalance. Sample collection dates 40 are known, allowing WSMV dating by RTDT methodology. most ancestor was dated at 1456 CE, cluster 1998.7 only 2–3 years before first reported. Tritimoviruses originated in central Eurasia, entering its Middle East domestication centre one lineage being taken to Mexico after Spanish conquest, whereas other spread throughout Iran, spreading world regions. Probable future regions additional phylogroups, interphylogroup recombinants, constitutes biosecurity concern.