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PLoS ONEZoologyPeer-reviewed journal article

Novel strains of tomato spotted wilt orthotospovirus (TSWV) are transmitted by western flower thrips in a context-specific manner

Senthilraja ChinnaiahiD, Arinder K. AroraiD, Kiran R. GadhaveiD

PDFDOIPreprint

In-depth summary

Claude Sonnet 4.6 · xhigh effort · 8 Nov 2026 · from the full text of version 1 (8 Apr 2025) · CC BY 4.0

Western flower thrips inoculated six TSWV strains across four sequential periods; males trended toward higher efficiency (87% vs 77% for resistance-breaking strains), but per-period differences were not significant.

Resistance-breaking TSWV strains defeat the Sw-5b and Tsw resistance genes worldwide, yet how thrips transmit them is largely unexplored. This work quantifies inoculation efficiency, sex differences, and titer relationships for six strains.

Key results

  1. SuggestedInoculation was highest in the first access period, fell afterward, and recovered by the fourth. Copy-number differences between periods were significant for some strains (Tom-BL1, Tom-BL2) but not others (Tom-MX, Pep-BL).

    Mean efficiency over IAP-I to IV: 92, 72, 70, 92% for resistance-breaking (RB) strains vs 95, 65, 65, 85% for Non-RB. Tom-BL1 copies in IAP-I exceeded IAP-II, III, IV (P<0.001). Tom-MX: P=0.363 (females), P=0.384 (males). · TSWV inoculation efficiency of F. occidentalis; Tom-BL1; Tom-BL2; Tom-MX

  2. SuggestedMales inoculated slightly more efficiently than females, and RB strains slightly more efficiently than the Non-RB strain. Per-period sex differences and the RB versus Non-RB gap were reported as not statistically significant.

    Overall efficiency: RB strains 87% (males) vs 77% (females); Non-RB 80% (males) vs 75% (females). Tom-CA 92.5% by males; Pep-BL and Tom-BL2 67.5% by females. Per-IAP differences were not significant, and the RB versus Non-RB gap was not statistically different. · TSWV inoculation efficiency of F. occidentalis; Abstract; Discussion

  3. ShownSome RB strains were inoculated at higher copy numbers than the Non-RB strain, in a strain-specific and period-specific way. Tom-MX showed no such difference.

    With sexes combined, Tom-BL1 and Tom-BL2 exceeded Non-RB in IAP-I (P<0.001) and IAP-IV (P=0.004). Tom-CA exceeded Non-RB in IAP-IV (P=0.004). Tom-MX did not differ from Non-RB in any IAP. · Tom-BL1; Tom-BL2; Tom-CA; Tom-MX

  4. SuggestedViral titers did not correlate between source tissue and thrips, or between thrips and the leaf discs they inoculated, in either sex. This points to within-vector propagation rather than acquired dose as the driver of inoculum.

    Thrips vs source tissue: females F=3.47, P=0.135, R^2=0.46; males F=3.61, P=0.130, R^2=0.47. Thrips vs inoculated discs: females F=1.27, P=0.321, R^2=0.24; males F=2.50, P=0.188, R^2=0.38. · Relationship of TSWV copies between source…; Discussion

  5. SuggestedTiters carried by adult thrips differed by strain. Tom-BL1 was highest and Pep-BL lowest after the inoculation periods. Tom-BL2 was highest before them. Titers did not differ between sexes.

    Post-IAP, with sexes combined: Tom-BL1 and Pep-BL differed from Non-RB (P<0.05). Pre-IAP: Tom-BL2 highest vs Non-RB (P=0.05). Male vs female comparisons within strains were not significant. · Pre-IAP; Post-IAP

Methods, data and reproducibility

First-instar thrips acquired each TSWV strain, and the resulting adults were moved one by one through four consecutive 24-h leaf-disc access periods. Viral N-gene copies in discs and thrips were measured by RT-qPCR and analyzed with GLMMs, Dunnett and Tukey tests, and regression.

  • Leaf discs inoculated by individual adult thrips over four consecutive access periods, six TSWV strains (five RB, one Non-RB); 10 replicates per sex per IAP per strain · Frankliniella occidentalis (vector); TSWV on tomato or pepper discs · n = 10 replicates/sex/IAP/strain; 20 discs/IAP/strain
  • Individual adult thrips assayed for TSWV copies before and after the inoculation periods · Frankliniella occidentalis · n = 10 per sex per strain
  • Source plant tissue (symptomatic tomato or pepper leaves) used for virus acquisition, compared with thrips and disc titers by regression · Tomato and pepper
Methods & tools
TaqMan Fast Virus 1-Step Master Mix RT-qPCR (nucleocapsid gene), QuantStudio 7 Pro, Plasmid standard curve for copy-number estimation, R 3.6.0, glmmTMB (GLMM), DescTools (Dunnett test), multcomp (Tukey test), Shapiro-Wilk test, Student's t-test, Regression analysis, glm for percent inoculation efficiency
Reagents & environment
R version 3.6.0 with the glmmTMB, DescTools and multcomp packages.
Reproducibility gaps
No code or data repository, supplementary data location, or availability statement appears in the text. Some strain mutation data are cited as unpublished.
Limitations (5)
  • The minimum viral copy number a thrips must acquire for successful inoculation is unknown. Whether leaf-disc inoculation translates to transmission in whole plants remains to be tested. · stated by the authors
  • Strains were maintained and tested on different plant cultivars (resistant tomato, pepper, susceptible tomato). The authors assume the 24-h assays were unaffected by cultivar but call for direct cultivar comparisons. · stated by the authors
  • Per-period efficiency differences between sexes were not statistically significant, nor was the higher efficiency of RB strains over the Non-RB strain. The authors say the biological implications of the latter are unclear. · stated by the authors
  • Only 10 thrips per sex per strain, from a single colony, give limited power for detecting sex effects on efficiency. The source-to-thrips-to-disc regressions appear to rest on few strain-level points, so the null correlations are weak evidence. · noted in this summary
  • The abstract says females carried higher titers, but the results report no significant male vs female titer difference in any strain, so that claim is weakly supported. · noted in this summary

Read this if you study thrips-vectored virus transmission, resistance-breaking TSWV strains, or sex differences in vector inoculation efficiency, and want quantitative baselines.

Citations
9
FWCI
4.84
Field percentile
top 5%

Abstract

Novel resistance breaking (RB) strains of tomato spotted wilt orthotospovirus (TSWV) capable of disrupting single gene resistance in tomato (Sw-5b) and pepper (Tsw) have been reported worldwide. Thrips, a supervector of TSWV, transmit these strains in a suite of specialty and staple food crops across the globe. However, transmission biology of RB strains remains virtually unexplored. We investigated various transmission parameters viz. inoculation efficiency, putative sex-specific differences in transmission, virus accumulation, and source sink relationships to dissect these interactions using six novel strains of TSWV, namely Tom-BL1, Tom-BL2, Tom-CA, Tom-MX, Pep-BL and Non-RB, transmitted by western flower thrips (WFT) over four 24h consecutive inoculation accession periods (IAPs). Our results show that most strains were inoculated at all four IAPs, however, their rates differed across IAPs. Overall, WFT had highest inoculation efficiency at the first and lowest at the second IAP. Female thrips carried higher virus titers; however, males were better at inoculating TSWV. Furthermore, we did not find significant positive correlations in virus titers between the tissues used for TSWV acquisition, thrips and thrips-inoculated leaf discs. Males inoculated RB strains at 87% efficiency whereas Non-RB strain at 80% efficiency. Female thrips were 77% and 75% efficient at inoculating RB and Non-RB strains, respectively. This study furnishes new insights into the transmission biology of TSWV RB strains, especially from inoculation and thrips sex perspectives, and provides a baseline for future molecular studies surrounding ever evolving novel TSWV strains.

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