Abstract from Fourth National Congress of Virology with International Participation /Days of Virology in Bulgaria Sofia, May 18th - 20th, 2016

Asztéria Almási, Gábor Csilléry, Katalin Nemes, Katalin Salánki, László Palkovics, István Tóbiás

Plant Protection Institute, Centre for Agricultural Research, HAS, Budapest, Hungary

Corvinus University of Budapest, Department of Plant Pathology, Budapest, Hungary

In Hungary resurgence of Tomato spotted wilt virus (TSWV) frequently causes heavy crop losses in pepper production since the mid nineties. Management of TSWV control was 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 is no conserved mutation present in all the NSs genes of RB isolates from different geographical origins. According to these results, we concluded that the RB isolates evolved separately in geographic point of view, and also according to the RB mechanism.

Gene silencing suppressor function of NSs protein is also discussed. In order to find new genetic sources of resistance in Capsicum species 89 lines from 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.