The discovery of five strains of TYLCV in Iran, including the most well-known and widespread, TYLCV-IL, spurred a detailed study of the full-length genomes of additional TYLCV field isolates and an in-depth analysis of phylogenetic relationships, extent of recombination, and genetic variability of TYLCV isolates within Iran and throughout the Arabian Peninsula. Phylogenetic analysis of complete genome sequences of TYLCV isolates from Iran and other countries revealed four monophyletic clusters could be differentiated based on geographical origin, indicating that recent dispersal of these populations (by the vector or by humans) from these four regions has occurred minimally, or not at all. Genetic analysis revealed that TYLCV-IL isolates from southern Iran possessed greater genetic variability than the northeastern isolates, a pattern that may be reflective of evolution driven by geographically dependent isolation. Similarly, isolates of TYLCV-OM originating from Oman showed greater genetic variability than TYLCV-OM variants from Iran. Major recombination events, which were detected in all strains of TYLCV had breakpoints initiating in the C1, C1/C4, C2/C3 and V1 open reading frames (ORFs) and ending at the non-coding region and the C1, C1/C2 and C3 ORFs. Hence, these regions have consistently served as hot spots for recombination worldwide during the evolution of all currently recognized isolates and strains of TYLCV.
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