The durable resistance gene Tm-22 remains partially resistant to tomato brown rugose fruit virus

A geminivirus betasatellite subverts the viral coat protein-mediated resistance to promote systemic infection

Viral coat protein (CP)-mediated resistance represents an effective strategy that confers robust antiviral defense in plants. However, the functional relevance of this resistance mechanism during mixed infections by distinct viral species remains largely elusive. Mixed viral infections in agricultural crops frequently lead to exacerbated disease symptoms and substantial yield losses, posing a severe threat to global agricultural production. In this study, we demonstrate that expression of tomato leaf curl New Delhi virus (ToLCNDV) CP confers effective resistance against tomato yellow leaf curl China virus (TYLCCNV), another prominent geminivirus. Strikingly, the βC1 protein encoded by TYLCCNV betasatellite can fully counteract this CP-mediated resistance through direct interaction with ToLCNDV CP and promotion of its proteasome-dependent degradation. We further identified the residue Tyr110 of βC1 as essential for the interaction and subsequent CP degradation. Consequently, βC1-mediated suppression of CP resistance promotes efficient systemic infection of ToLCNDV DNA A. Collectively, our results uncover a novel mechanism by which a viral effector antagonizes viral CP-mediated host resistance during mixed viral infections, offering important insights into viral pathogenesis and the development of sustainable disease control strategies.

A Novel Approach to Engineering Tomato Spotted Wilt Virus Infectious Clones by Disarming Key Nodes in Anti-Viral Defenses.

Tomato spotted wilt virus (TSWV) is an economically devastating pathogen that rapidly overcomes genetic resistance in major crops. Reverse genetic systems are crucial for investigating plant-virus interactions and resistance breaking mechanisms, and developing these tools for segmented ambisense RNA viruses remains a crucial challenge. Current TSWV-clones rely on extensively modified Asian isolates requiring co-delivery of multiple replication helpers and viral silencing suppressors. Streamlining these systems for regionally significant strains with minimal genetic alterations is essential. Here we developed the first infectious clone of a USA TSWV isolate (PA01). Three binary plasmids contain cDNAs for the antigenomic L and S segments, and the genomic M segment, with enhanced GFP replacing NSs on the S segment. Co-delivery of the cucumovirus 2b alone or in combination with tombusvirus P19 or begomovirus AL2, achieved a high proportion of systemically infected Nicotiana benthamiana and Capsicum annuum plants. In N. tabacum, co-delivering the Caenorhabditis elegans cell death suppressor CED-9, or using NahG transgenic plants produced 20 to 62% systemically infected plants. These data indicate that in addition to the anti-viral RNA silencing machinery, additional host defense pathways influence TSWV rescue and systemic infection from cDNA.

Integrated transcriptome and metabolome analysis of resistant and susceptible tomato cultivars in response to tomato mottle mosaic virus and functional characterization of snakin-2 in viral defense.

Tomato mottle mosaic virus (ToMMV) is an emerging tobamovirus causing severe losses in tomato production. To elucidate host resistance mechanisms, we compared two tomato cultivars with contrasting responses to ToMMV using integrated transcriptomic, metabolomic, and functional analyses. The resistant line (R) carried resistance gene Tm‑2² at extremely low levels, while the susceptible line (S) did not; both lines highly expressed susceptibility gene tm-2. R plants exhibited minimal viral accumulation and maintained chlorophyll levels, whereas S plants showed high viral load and chlorophyll degradation. Multi-omics revealed that in S, ToMMV primarily disrupted chlorophyll biosynthesis and photosynthesis, while activating multiple defense pathways, including plant-pathogen interaction, phenylpropanoid/flavonoid biosynthesis, and MAPK signaling. In R, a broader activation of plant-pathogen interaction and phosphatidylinositol signaling pathways was observed, alongside early upregulation of SlSN2. The abundance of phenolic acids, notably caffeic acid, ferulic acid, and sinapic acid, was significantly higher in R than in S. Integrated transcriptomic and metabolomic analyses showed that both differential genes and metabolites were co-enriched in the phenylpropanoid biosynthesis pathway. Functional assays demonstrated that SlSN2 overexpression suppressed ToMMV accumulation and infection, likely via enhanced lignin biosynthesis. These findings suggest a potential role for SlSN2 in contributing to ToMMV resistance, independent of the known Tm‑2² pathway. This work identifies SlSN2 as a candidate factor for further evaluation in the prevention of ToMMV.

Reverse genetics platform for tomato mottle mosaic virus: infectious clone construction and resistance screening in tomato

Detection and Heritability of Genes Conferring Resistance to Potato Pests and Viruses in Hybrid Potato Progeny (Solanum tuberosum L.)

Potato viral infections are among the main factors contributing to reduced quality of planting material and decreased tuber productivity. Currently, no reliable chemical control methods are available for plant viral diseases. Therefore, the development of potato cultivars carrying virus resistance genes remains one of the most effective and comprehensive approaches to this problem. In this study, 29 Russian and foreign potato cultivars, as well as 31 Far Eastern potato hybrids were evaluated. Resistance genes were identified using PCR analysis. The following cultivars carrying target resistance genes were used as positive controls for method calibration: Meteor (Rysto, Rx1, Sen1, Gpa2, H1), Vektor (Rx1, Gpa2), Yubilyar (Gpa2), and Zhukovsky ranniy (Gpa2, Rx1). Method calibration enabled determination of optimal magnesium chloride concentrations: 2.0 mM for Gpa2 and 2.5 mM for Rx1. Genotyping of 29 potato cultivars identified several highly resistant accessions, including Yubilyar, Zhukovsky ranniy, Bellarosa, Sante, Smak, Red Scarlett, and Laperla. These cultivars combined resistance to Potato virus X (Rx1) with complex resistance to two nematode species (Gpa2, H1). In the studied population, high frequencies of the Gpa2 (82.8%) gene and the H1 (65.5–69.0%) gene group were observed. Statistical analysis provided strong evidence for tight genetic linkage between the Rx1 and the Gpa2 loci on chromosome 12. The association was highly significant (p < 0.001). Analysis of 31 potato hybrids revealed 14 multi-marker genotypes with high breeding potential. A stable combination of five target resistance markers was consistently detected in their genomes. A dominant hybrid family derived from the Yantar × Smak cross was identified, represented by five related lines. For the first time, a precise heritability coefficient was calculated for the STS marker of the Rx1 gene in a Far Eastern hybrid population. The estimate reached h2 = 0.835 at p = 0.01. This value significantly exceeded the critical threshold for breeding reliability (h2 > 0.7), indicating largely additive genetic control of the trait. These results support targeted selection of parental combinations for breeding programs aimed at improving virus and nematode resistance in potato.

A dominant mutation in tomato DNA POLYMERASE DELTA 1 causes geminivirus DNA replication catastrophe.

Geminiviruses pose a severe threat to grain and vegetable crops worldwide, often resulting in significant economic losses. In cultivated tomato (Solanum lycopersicum), Ty resistance alleles have been introduced from wild tomato relatives, providing partial to strong resistance to geminivirus infections. The Ty-6 resistance locus from Solanum chilense was previously mapped to chromosome 10. It was recently shown to contain a mutant allele of the DNA POLYMERASE DELTA 1 (POLD1) gene that provides resistance to Tomato yellow leaf curl virus (TYLCV) infections. However, the resistance mechanism remained unknown. Here, we report another POLD1 allele at the Ty-6 locus of S. chilense with an E622D mutation in the catalytic site of the POLD1 protein. POLD1E622D is maintained as a heterozygous dominant allele in S. chilense and the AVTO2225 breeding line. It provides full resistance to the severe TYLCV Thailand (TYLCTHV) strain. The E622D amino acid change does not alter the predicted structure of POLD1. Replication of the TYLCTHV genome in plants carrying the POLD1E622D allele is severely compromised by a high frequency of mutations that accumulate in viral DNA, which results in nonfunctional proteins that are essential for continuous viral replication. Ectopically expressing the POLD1E622D allele cDNA alone causes mutations in TYLCTHV genes in inoculated leaves. S. chilense and AVTO2225 plants carrying the POLD1E622D allele mount a hypersensitive response after TYLCTHV infection, indicating that the defective virus genome cannot suppress the plant defense. The dominant POLD1E622D allele is therefore an effective resistance gene that geminiviruses cannot overcome.