Tomato spotted wilt virus (TSWV) resistance in tomato derived from Lycopersicon chilense Dun. LA 1938

Tomato spotted wilt virus (TSWV) resistance was identified in Y118 (Fla 925-2), an F1BC1S6 tomato line ( Lycopersicon esculentum Mill.), derived from a cross with L. chilense Dun. (LA 1938). This line was previously selected for tomato mottle virus (ToMoV) resistance in Florida. Progeny from crosses between Fla 925-2 and three different TSWV susceptible L. esculentum parents were used in TSWV resistance studies. A total of 75 F-1 and 596 F-2 plants from all three crosses were screened for TSWV resistance. For F-2 plants free of TSWV symptoms, evaluations were made using enzyme-linked immunosorbent assay (ELISA). Ten F-3 populations used for further greenhouse and field screenings were selected from F-2 plants found to be free of the virus using visual and ELISA criteria at each evaluation. One F-1 and four F-3 lines were studied under field conditions (Stellenbosch, South Africa) in which 100% of the 'Flora-Dade' susceptible controls were severely infected with TSWV. The results of the field study clearly establish that TSWV field resistance is present in the Fla 925-2 (Y118) derived lines. Studies conducted on these lines revealed that this resistance has the distinct characteristic of often 'recovering' from initially high levels of virus titer in the tissue to levels below detection with ELISA.