Middle East traced as global hub spreading tobacco mild green mosaic virus

Tobacco mild green mosaic virus, a globally distributed tobamovirus that threatens solanaceous crops, appears to have spread worldwide from a Middle Eastern origin, according to a phylogeographic reconstruction published in Virology Journal. The brief report by Shuling Zhang, Guyuan Lin, Xueying Huang and Huiquan Wang used the MASCOT-Skyline structured coalescent framework to reconstruct the evolutionary history of the pathogen.

The analysis estimated the mean substitution rate for the virus’s coat protein gene at 3.89 × 10−4 substitutions per site per year, with a 95% credibility interval running from 2.17 × 10−4 to 5.71 × 10−4. This rate allowed the researchers to place a timescale on the virus’s diversification, tracing the origin of the current TMGMV population to the Middle East around the year 1876.

Bayesian phylogeographic reconstruction identified the Middle East as the most likely spatial origin of TMGMV with a support value of RSPP = 0.86. The region also functioned as a primary hub seeding migrations outward: viral lineages moved into Asia between 1949 and 2012, into Europe between 1962 and 1999, and into the Americas between 1982 and 2018. These date ranges indicate that dispersal out of the hub was not a single event but a repeated process spanning more than a century.

The study also examined the demographic history of the virus. The analysis indicated that TMGMV populations have remained largely stable across their global range, with only minor regional fluctuations, a pattern consistent with a pathogen that persists steadily in solanaceous crops and related hosts rather than producing repeated epidemic waves.

The phylogeographic method treats sampled viral sequences as tips of a time-scaled evolutionary tree and infers where ancestral lineages were located. The MASCOT-Skyline framework models population sizes and migration rates as changing through time, suited to pathogens whose spread has been shaped by changing patterns of agriculture and trade. By combining this structured coalescent model with Bayesian inference, the researchers could estimate the probability that each ancestral lineage occupied a particular geographic region, producing the RSPP support value and the dated migration windows.

The finding that the current population traces to around 1876 places the ancestral population well before modern molecular detection, so the reconstruction relies on the assumption that the estimated substitution rate has remained sufficiently constant to serve as a molecular clock. Credibility intervals around such estimates can be wide, and the dated origin should be read as a statistical estimate rather than a precise historical record. Similarly, the migration windows represent the most likely periods of viral movement supported by the sampled sequences, not documented dates of first introduction, since unsampled lineages could have circulated elsewhere without leaving sequence records.

The authors describe these results as providing critical insights into the complex spatio-temporal dynamics of TMGMV and highlighting the pivotal role of the Middle East in its worldwide spread. For plant health authorities, such a phylogeographic picture can clarify how a crop pathogen achieved its global distribution and which routes of movement were most important, information relevant to surveillance and to the management of seed-borne tobamoviruses in solanaceous crops.

The report was published as an open access article on 30 October 2026, and the version shared at that date is an early release of peer-reviewed, accepted research that carries a permanent DOI and remains subject to further edits before the final Version of Record appears.

Subject of Research: Phylogeographic reconstruction of the global spread of tobacco mild green mosaic virus from a Middle Eastern origin

Article Title: The Middle East as a global hub for the dissemination of tobacco mild green mosaic virus: Insights from phylogeographic reconstruction

Article References: Zhang, S., Lin, G., Huang, X., & Wang, H. (2026). The Middle East as a global hub for the dissemination of tobacco mild green mosaic virus: Insights from phylogeographic reconstruction. Virology Journal. https://doi.org/10.1186/s12985-026-03338-4

Image Credits: AI Generated

DOI: 10.1186/s12985-026-03338-4

Keywords: tobacco mild green mosaic virus, TMGMV, tobamovirus, phylogeography, Middle East, MASCOT-Skyline, structured coalescent, substitution rate, coat protein gene, plant virus, solanaceous crops, viral migration