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Hungary: New type of resistance breaking strain of tomato spotted wilt virus (TSWV)

03/03/2023

François-Xavier Branthôme
Hungary,
WPTC
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 Researchers from Plant Protection Institute (Centre for Agricultural Research, Eötvös Loránd Research Network, in Budapest, Hungary) and Univer Product Plc. (Kecskemét, Hungary) isolated and identified a new type of resistance breaking strain of tomato spotted wilt virus (TSWV) in Hungary. The results were published in the European Journal of Plant Pathology in February.

Sw-5b is a widely used resistance gene in tomato breeding to control tomato spotted wilt virus (TSWV). The NSm protein encoded by TSWV is identified as the avirulence (AVR) determinant in Sw-5b-mediated resistance. In the last decades, Sw-5b resistance breaking (RB) isolates were found and identified in many locations around the world. The resistance-breaking phenotype in all the previously verified TSWV Sw-5b RB strains is associated with the NSmC118Y or NSmT120N mutations. In the summer of 2022, an Sw-5b RB TSWV strain was recognized in a greenhouse in Hungary. In inoculation experiments, this strain was able to infect tomato plants with the Sw-5b resistance gene. Molecular analysis of the NSm avirulence determinant revealed a single alteration in the NSm protein, D122G mutation was identified. This is the first report to identify this amino acid alteration associated with resistance-breaking phenotype in Sw-5b resistant tomato plants [1].

“Previously Sw-5b RB TSWV strain was not recognized in Hungary even if it was detected in several European countries in the last decade. The origin of this strain is still in question as it is the first detection of this new mutant strain. It could have developed locally, but it is also feasible that it was introduced from another area, where it has not been identified previously. Monitoring the spread of this new mutant is of primary importance in the future” – said prof. Katalin Salánki, head of the Department of Plant Pathology, Plant Protection Institute.

“We do not deal with tomato resistance breeding, only peppers. However, in the course of our tomato variety experiments and gene preservation activities, we pay a lot of attention to plant diseases and the microorganisms that cause them. Whenever possible, we isolate all viruses and bacteria whose investigation with our partners can expand the knowledge of host-pathogen interaction and plant resistance” – said Gábor Palotás, head of R&D Department of Univer Product Plc.

Tomato Spotted Wilt Virus
If the wide range of host plants is combined with high pathogenicity, rapid adaptability, and great epidemiological potential, such "superviruses" can emerge that are very difficult to defend against and can only be defended by applying a complex strategy. Tomato spotted wilt orthotospovirus (TSWV) can be classified as one of these viruses.

TSWV is one of the earliest discovered plant viruses. The serious disease caused by it, spotted wilt of tomatoes, was first observed in 1915 in the Australian state of Victoria. The viral origin of the disease was confirmed in 1930. Today, TSWV has spread on susceptible crops on all continents, primarily vegetables (tomatoes, peppers, lettuce), ornamentals (e.g. chrysanthemums, begonias), and many field crops (e.g. peanuts, tobacco). In some cultures, it can cause yield losses of up to 50-90% and often the death of plants. The damage it causes worldwide is estimated at one billion dollars a year [2].

Some complementary data and sources

[1] Asztéria Almási, Dóra Pinczés, Zoltán Tímár, Réka Sáray, Gábor Palotás, Katalin Salánki: Identification of a new type of resistance breaking strain of tomato spotted wilt virus on tomato bearing the Sw 5b resistance gene. European Journal of Plant Pathology https://doi.org/10.1007/s10658-023-02656-5 

[2] Pál Salamon, Judit Magyari: Tomato Spotted Wilt Virus – A „supervirus with supervector”. Agroforum Online (https://agroforum.hu/szakcikkek/novenyvedelem-szakcikkek/paradicsom-foltos-hervadas-virus-szupervirus-szupervektorral/ – in Hungarian)
 

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