Phenotypic Variation for Resistance to Tomato Spotted Wilt Virus In Pepper

Resistance to TSWV in pepper has been documented from Capsicum chinense accessions PI 152225 and PI 159236.  The dominant Tsw gene has been introduced into several commercial cultivars but it frequently fails to prevent systemic infection, depending on thrips pressure and the genetic background of the cultivar. We have recently documented novel resistance phenotypes in Capsicum annuum. Currently we are evaluating the genetic inheritance of the genes involved. Based on F1 hybrid data, there appears to be a strong dominant component. However, unlike with Tsw, there has not been any hypersensitive reaction with local lesions.  In addition we also recorded extreme differences in the time required for the virus to become systemic, in lines carrying Tsw and others without this locus.  We have developed inbred lines of C. chinense which contain Tsw with relatively short periods until breakdown of the hypersensitive response, and others which have never demonstrated systemic infection after 8 months of viruliferous thrips infestation in the greenhouse. The same phenomenon has been observed with C. annuum lines which do not have the Tsw gene.  Finally, we have recorded a tendency of some lines, including several derived from C.chinense x C. annuum crosses, to recover from systemic necrosis, while adjacent susceptible lines continued to develop more severe symptoms and even die. We have developed some unique inter-specific hybrids to combine the different resistance genes and these lines have demonstrated excellent durability in our inoculated screening tests compared to any commercially available hybrids with the Tsw gene.  In addition we have developed two new F1 hybrid Habanero cultivars with extremely durable TSWV resistance. These cultivars contain the Tsw gene introgressed into C. chinense lines which previously had demonstrated excellent field resistance to TSWV, heat tolerance, early maturity and heavy yields.  In addition to TSWV, one of the cultivars is homozygous recessive for the pvr1 locus, providing resistance to PepMoV and TEV.