Texas TSWV isolate loses detectable Tsw recognition but retains tomato resistance

A tomato spotted wilt virus isolate collected from Bushland, Texas, can overcome resistance associated with the Tsw immune receptor in pepper, according to a study of pepper-associated viruses from three Texas locations. The isolate, designated HTPepRB, systemically infected two pepper genotypes containing Tsw, whereas an isolate from Uvalde did not. HTPepRB remained unable to overcome Sw-5b-mediated resistance in tomato, indicating that its resistance-breaking behavior in pepper did not extend to the separately tested tomato resistance system.

Researchers characterized the three isolates using whole-genome sequencing, phylogenetic analysis, transient expression of the viral NSs protein, host infectivity assays, and population-level comparisons of NSs and NSm sequences. These methods connected the phenotype of each complete virus with the activity of its effector protein. The study centered on NSs, a viral protein recognized by Tsw, and NSm, a viral movement protein in which several substitutions have previously been associated with breakdown of Sw-5b resistance in tomato. By comparison, the sequence changes underlying escape from Tsw-mediated recognition were less clearly resolved.

The behavior of HTPepRB was consistent with its NSs protein. Transient expression of HTPepRB NSs failed to elicit a detectable Tsw-dependent hypersensitive response. NSs proteins from the Uvalde and College Station isolates retained this avirulence activity, showing that Tsw could still detect those versions of the protein. The results therefore link the loss of detectable Tsw-dependent recognition of HTPepRB NSs with the whole-virus resistance-breaking phenotype in Tsw-containing pepper. This association was established in the isolates and experimental systems tested; it does not demonstrate that the same phenotype occurs in other locations or plant populations.

Across field-derived sequences from the three collection sites, NSs displayed greater amino acid variation and more differentiation associated with location than NSm. The analysis identified several substitutions enriched in the Bushland population, as well as substitutions also found in previously reported resistance-breaking isolates. Those overlaps nominate the changes as candidates for involvement in altered Tsw recognition, but the experiments did not establish that any individual substitution caused resistance breaking. Only HTPepRB was functionally linked to Tsw resistance breakdown, so the researchers did not treat the associated NSs sequence changes as confirmed causal determinants.

The findings distinguish two tested resistance outcomes: HTPepRB escaped Tsw-mediated recognition and established systemic infection in Tsw-containing pepper, while remaining restricted by Sw-5b-mediated resistance in tomato. They also identify divergent NSs sequence backgrounds as material for future functional dissection of Tsw–NSs recognition. The population analysis shows where variation occurred and which changes are candidates, but it does not resolve the contribution of each substitution. Accordingly, the study offers a characterized resistance-breaking isolate and a set of candidate sequence variants, rather than a validated marker or a general mechanism for evading plant resistance.

Subject of Research: Functional and genomic characterization of a Tsw resistance-breaking tomato spotted wilt virus isolate

Article Title: Functional and genomic characterization of a Tsw resistance-breaking tomato spotted wilt virus isolate links loss of NSs recognition with divergent NSs sequence variation

Article References: Kumar, S., Singh, R. M., & Gadhave, K. R. (2026). Functional and genomic characterization of a Tsw resistance-breaking tomato spotted wilt virus isolate links loss of NSs recognition with divergent NSs sequence variation. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10204-6

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DOI: 10.1186/s12870-026-10204-6

Keywords: tomato spotted wilt virus, Tsw resistance, pepper immunity, NSs protein, Sw-5b resistance, plant virus genomics, resistance breaking, whole-genome sequencing, phylogenetic analysis, Functional, genomic, characterization