 TBSV was first discovered in 1935 in tomatoes and results in plants with stunted growth and deformed fruits.TSWV was discovered in tomatoes in Australia in 1915, and for many years was the only member of what is now known as genus "Tospovirus", family "Bunyaviridae".In order to defend itself against viruses and other pathogens that introduce foreign nucleic acids into their cells, plants have developed a system of post-transcriptional gene silencing (PTGS) where small interfering RNAs are produced from double-stranded RNA in order to create a sequence specific degradation pathway that efficiently silence non-native genes.