TSWV resistance-breaking isolates infecting pepper in Argentina

FERRAND, M.M. ; SEVERO DE ALMEIDA, A. F. ORILIO, R.O. RESENDE; MARIA LAURA GARCIA ; P. A. BALATTI & E. DAL BÓ

Congreso; Congreso Internacional de Tospovirus; 2015

The disease caused by Tomato spotted wilt virus (TSWV) is endemic on vegetable crops in Buenos Aires green belt, the most important vegetable production area in Argentine. Half of the greenhouse surface planted with sweet pepper (Capsicum annuum L.) in the country there. In November 2014, peppers harboring the Tsw resistance gene showing typical tospovirus symptoms were observed. Symptoms appeared 20 days after transplanting in early spring and by midsummer 100% of the plants were affected in many greenhouses, causing important economic losses. Samples from symptomatic plants were analyzed by ELISA with antisera against TSWV, Groundnut ringspot virus (GRSV), Tomato chlorotic spot virus (TCSV), Potato virus Y (PVY), Cucumber mosaic virus (CMV) and Tobacco mosaic virus (TMV). All samples were positive for TSWV and negative for the rest. Presence of TSWV was confirmed by RT-PCR with primers designed from conservative region of the N gene and by molecular hybridization of dot blot. To test the ability to overcome the resistance, this greenhouse-isolate named TSWV-A2, was mechanically transmitted to commercial pepper cultivars carrying the Tsw gene. After two weeks, all plants were systemically infected showing the typical symptoms of TSWV infection. RT-PCR from total RNA extracted from symptomatic leaves, confirmed that TSWV-A2 was able to overcome Tsw gene resistance. Further to amplify the complete N gene of TSWV-A2 isolate, a new RT-PCR was carried out. A specific 800 bp product was cloned and sequenced. Comparison of this sequence with TSWV sequences in the GenBank showed the closest identity (99% in the nucleotide and in the amino acid sequence) to the isolates EF195230 and EF195224 from South Korea. In addition, TSWV-A2 showed to share common characteristics with the resistant-breaking isolates infecting resistant sweet pepper cultivars, previously reported in Italy and Spain.