Identification and characterization of Tomato spotted wilt orthotospovirus pro-viral factors as a source for durable resistance

Tomato spotted wilt orthotospovirus (TSWV) and related tospoviruses are plant pathogenic viruses that cause extensive crop losses worldwide. Unfortunately, dominant resistance loci against TSWV appear to be (1) scarce, (2) absent in many plant species, and (3) rapidly overcome by resistance breaking isolates of the virus. Therefore, there is an urgent need for growers and our society to discover alternative forms of TSWV resistance. One approach in achieving this is to remove or mutagenize host factors that are essential in the viral infection cycle, which in turn, can convert an otherwise susceptibility host into a non-host for TSWV. Such a pro-viral host factor is also referred to as susceptibility (S)-gene and, hence, applied mutant alleles of S-genes can render durable resistance to TSWV in crops. To identify S-genes for TSWV, a detailed understanding is needed of the host factors hijacked by the virus during its infection cycle. The research presented in this PhD thesis describes different efforts to identify and characterize novel host factors required for the infection cycle of TSWV in order to better understand the molecular interaction between the plant and the virus. These findings can ultimately be applied as a resource of recessive viral resistance in breeding programs. In total, four methods are here presented by which host factors were identified and their role during viral infection in plants was investigated. The pros and cons of the methods applied are discussed together with the applicability of the identified host factors as a novel source for viral resistance.