Just can’t resist: resistant host succumbs to virus when vector feeds on reproductive host tissue

The control of vector-borne diseases in crops through host-plant resistance can be compromised by vector feeding on host tissue with reduced expression of resistance to the pathogen. Tomato spotted wilt virus (TSWV) infects tomatoes (Solanum lycopersicum) causing serious economic losses worldwide. Thrips (Family: Thripidae) transmit TSWV to young tomato plants by feeding on vegetative tissue. Plant maturity and the Sw-5 resistance gene provide a high level of resistance against the virus, but late season outbreaks of TSWV can still occur in tomato fruit. We hypothesized that feeding on reproductive tissue by the western flower thrips (Frankliniella occidentalis) renders the host unable to resist infection even in the presence of the Sw-5 resistance gene. Isolates of TSWV were thrips-inoculated into the reproductive tissue of mature tomato plants with and without the Sw-5 gene using F. occidentalis. There was a high rate of fruit infections in both host genotypes. There was also a large proportion of systemic infections, allowing virus to move to other fruit. The reproductive tissue provides an entry point for TSWV to infect tomatoes with Sw-5 mediated resistance and mature plant resistance. Feeding by viruliferous thrips on the reproductive tissue of tomato plants can result in substantial late season losses in marketable fruit.