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Molecular evolutionary genomics and population structure of Iris yellow spot orthotospovirus (Family: Tospoviridae; Genus: Orthotospovirus)

Afsha Tabassum: Department of Plant Pathology, Washington State University

<div><em>Iris yellow spot orthotospovirus</em> (IYSV) is an important virus of <em>Allium </em>sps. Using the global repository of IYSV nucleoprotein (N) gene sequences available in GenBank (a total of 142), temporal dynamics and geographic diversity of the IYSV isolates were investigated to gain better insights into the evolutionary forces influencing genetic population structure of IYSV. Based on <em>In Silico </em>Restriction Fragment Length Polymorphism (RFLP), N gene sequences showed a 79:55 distribution of known IYSV isolates into two major genotypes, IYSV Netherlands (IYSV<sub>NL</sub>; 55.63% ) and IYSV Brazil (IYSV<sub>BR</sub>; 38.73%). A little over five percent of the isolates fell in neither group [IYSV other (IYSV<sub>other</sub>; 5.63%)]. Phylogenetic tree and phylogenetic networks largely corresponded to the RFLP pattern. Nucleotide diversity comparisons indicated IYSV<sub>BR</sub> to be least differentiated from IYSV<sub>other</sub> compared to the IYSV<sub>NL</sub> type. Two recombinants were detected among all the N gene sequences that were analysed through RDP4 and RAT programs. The marginal likelihood mean substitution rate was 5.09x10<sup>-5</sup> subs/site/year and 95% highest posterior density (HPD) substitution rate between 5.11x10<sup>-5</sup> – 5.07x10<sup>-5</sup>. The substitution rate identified for IYSV N gene is similar to other plant RNA viruses. Evolution studies of IYSV will help to understand the disease epidemiology and design appropriate disease control measures.</div>