Molecular characterization of resistance breaking tomato spotted wilt virus ( TSWV ) isolate in the tomato plant

Tomato Spotted Wilt Virus (TSWV) is one of the plant viruses that spreads rapidly with thrips vectors and causes the most common and economically important yield losses in worldwide. Sw-5gene in tomato and Tsw genes in pepper are responsible for the resistance towards TSWV. However, it has recently been reported that resistance to these genes broken allowing spreads of TSWV infections on tomato varieties with Sw-5 and Tsw resistance genes in many parts of the World. The main purpose of this study was to understand the mechanism of the breaking of TSWV resistance in tomato varieties with the resistance genes in Turkey.The resistance-breaking TSWV isolate (TSWV AntRB) was collected and its whole genom sequences were compared with those of the World's TSWV isolates in order to establish phylogenetic trees and find out a mutation which breaks the Sw-5 gene resistance. Based on the whole genome sequences, the TSWV genome has consisted of three-part segmented structures which were: Large segments-8913 nt, Medium-4752 nt and Small-2924 nt length regions. Their three regions coding proteins were amplified by RT-PCR, and their sequences were obtained. Open reading regions responsible for protein synthesis were identified on the gene sequences. Differences in nucleotides, amino acid and protein levels were revealed in these regions. There was a mutation on non-structural protein (NSm) region. The NSm region is responsible cell to cell movement where a mutation at the C118Y site on the NSm domain has been determined. These mutations allow breaking of resistance. Additionally, the comparisons of the M and S segments (TSWVAntRB) have showed 99% similarity with those of the virus isolates broken resistance in Spain. It has been determined that analysis located the virus on the same root and same branch in the same place. The phylogentic trees have shown us that the isolate TSWVAntRB has come from the same origin in Europe.