Tomato Spotted Wilt Virus on Pepper (Capsicum annuum L.) Plants in Hungary. Molecular Characterization of Wild Type and Resistance Breaking Isolates. Searching for Resistance in Capsicum Genus
Authors: Almási, A., Csilléry, G., Nemes, K., Salánki, K., Palkovics, L., Tóbiás, I.
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In Hungary resurgence of Tomato spotted wilt virus (TSWV) has been frequently causing heavy crop losses in pepper production since the mid-nineties. Management of TSWV was at first directed against thrips (using different insecticides or plastic traps), and against weeds as host plants of the virus and the thrips. Later on, Tsw resistance gene was introduced into different types of pepper. In 2010 and 2011, sporadically, but in 2012 more frequently a resistance breaking (RB) strain of TSWV on resistant pepper cultivars was observed in the Szentes region (South-East Hungary). The presence of a new resistance breaking strain was demonstrated by virological (test-plant, serological and RT-PCR) methods.
Previously, the non-structural protein (NSs) encoded by small RNA (S RNA) of TSWV was verified as the avirulence factor for Tsw resistance, therefore we analyzed the S RNA of the Hungarian RB and wild type (WT) isolates, and compared to previously analyzed TSWV strains with RB properties from different geographical origins. Phylogenetic analysis demonstrated that the different RB strains had the closest relationship with the local WT isolates and there was no conserved mutation present in any of the NSs genes of RB isolates from different geographical origins. According to these results, we concluded that the RB isolates evolved separately from a geographic point of view, and also according to the RB mechanism. The gene-silencing suppressor function of NSs protein is also discussed.
In order to find new genetic sources of resistance in Capsicum species 89, lines of Capsicum annuum, C. chinense, C. frutescens, C. chacoense, C. baccatum var. baccatum, C. baccatum var. pendulum and C. praetermissum were tested with TSWV-RB strain isolated in Hungary..