In Hungary resurgence of Tomato spotted wilt virus (TSWV) frequently causesheavy crop losses in pepper production since the mid nineties. Management ofTSWV control was first directed against the thrips (using different insecticides orplastic traps), and against weeds as host plants of the virus and the thrips. Later onTsw resistance gene was introduced from Capsicum chinense PI 152225 and PI159236 into different types of pepper. In 2010 and 2011 sporadically, but in 2012more frequently a resistance breaking (RB) strain of TSWV on resistant peppercultivars was observed in the Szentes region (South-East Hungary). The presenceof 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 forTsw resistance, therefore we analyzed the S RNA of the Hungarian RB and wildtype (WT) isolates and compared to previously analyzed TSWV strains with RBproperties from different geographical origins. Phylogenetic analysis demonstratedthat the different RB strains had the closest relationship with the local WT isolatesand there was no conserved mutation present in all the NSs genes of RB isolatesfrom different geographical origins. According to these results, it is concluded thatthe RB isolates evolved separately in geographic point of view and according to theRB mechanism. In order to find new genetic sources of resistance in Capsicumspecies 89 lines from Capsicum annuum, C. chinense, C. frutescens, C. chacoense,C. baccatum var. baccatum, C. baccatum var. pendulum and C. praetermissumwere tested with the Hungarian TSWV-RB isolate.
First report in Italy of a resistance-breaking strain of Tomato spotted wilt virus infecting tomato cultivars carrying the Sw5 resistance gene