Articles
Characterization of a new type of resistance breaking TSWV strain isolated from tomato in Hungary
Article number
1445_48
Pages
347 – 352
Language
English
Abstract
The worldwide use of the resistance gene Sw-5b in tomato breeding is an effective method against Tomato spotted wilt orthotospovirus (TSWV, synonym Orthotospovirus tomatomaculae) epidemics.
NSm protein (movement protein, MP) encoded by the M RNA of TSWV was previously identified as the avirulence determinant against Sw-5b gene in tomato.
In the last decades, Sw-5b resistance breaking (RB) TSWV isolates have been identified in several countries in the world.
In the case of the previously described TSWV Sw-5b RB strains, the resistance breaking phenotype was the result of point mutations C118Y and/or T120N of the MP. In summer of 2022, we recognized a resistant tomato plant carrying the Sw-5b gene showing TSWV-like symptoms in a plastic tunnel in Kecskemét, Hungary.
Test plant bioassays were carried out with the collected sample.
Both resistant and susceptible tomato cultivars were inoculated and, in both cases systemic symptom development was observed 6-8 days after inoculation.
The NSm avirulence gene was amplified by RT-PCR method and after nucleotide sequence determination, the mutation responsible for the RB phenotype was identified.
Phylogenetic analysis and amino acid sequence comparison of the NSm were assessed with 7 RB and 8 normal (NI) TSWV strains retrieved from the NCBI GeneBank and the location of the Hungarian RB isolate in the ML tree and the relationship to the other isolates was evaluated.
Comparison of the amino acid sequences of the Hungarian resistance breaking and the normal isolates revealed a unique D122G alteration in NSm protein that has not been detected previously in any of the resistance breaking TSWV strains.
Based on the phylogenetic analysis, we concluded that this isolate grouped together with the isolates of Clade 1.
NSm protein (movement protein, MP) encoded by the M RNA of TSWV was previously identified as the avirulence determinant against Sw-5b gene in tomato.
In the last decades, Sw-5b resistance breaking (RB) TSWV isolates have been identified in several countries in the world.
In the case of the previously described TSWV Sw-5b RB strains, the resistance breaking phenotype was the result of point mutations C118Y and/or T120N of the MP. In summer of 2022, we recognized a resistant tomato plant carrying the Sw-5b gene showing TSWV-like symptoms in a plastic tunnel in Kecskemét, Hungary.
Test plant bioassays were carried out with the collected sample.
Both resistant and susceptible tomato cultivars were inoculated and, in both cases systemic symptom development was observed 6-8 days after inoculation.
The NSm avirulence gene was amplified by RT-PCR method and after nucleotide sequence determination, the mutation responsible for the RB phenotype was identified.
Phylogenetic analysis and amino acid sequence comparison of the NSm were assessed with 7 RB and 8 normal (NI) TSWV strains retrieved from the NCBI GeneBank and the location of the Hungarian RB isolate in the ML tree and the relationship to the other isolates was evaluated.
Comparison of the amino acid sequences of the Hungarian resistance breaking and the normal isolates revealed a unique D122G alteration in NSm protein that has not been detected previously in any of the resistance breaking TSWV strains.
Based on the phylogenetic analysis, we concluded that this isolate grouped together with the isolates of Clade 1.
Authors
A. Almási, D. Pinczés, Z. Tímár, R. Sáray, G. Palotás, K. Salánki
Keywords
tomato spotted wilt virus (TSWV), tomato, resistance breaking (RB), resistance breeding, NSm, movement protein (MP), Solanum lycopersicum, Sw-5b resistance gene
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