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 paren ts were used in TSWV resistance studies. A total of 75 F-1 and 596 F-2 plan ts from all three crosses were screened for TSWV resistance. For F-2 plants free of TSWV symptoms, evaluations were made using enzyme-linked immunosor bent assay (ELISA). Ten F-3 populations used for further greenhouse and fie ld screenings were selected from F-2 plants found to be free of the virus u sing visual and ELISA criteria at each evaluation. One F-1 and four F-3 lin es were studied under field conditions (Stellenbosch, South Africa) in whic h 100% of the 'Flora-Dade' susceptible controls were severely infected with TSWV. The results of the field study clearly establish that TSWV field res istance is present in the Fla 925-2 (Y118) derived lines. Studies conducted on these lines revealed that this resistance has the distinct characterist ic of often 'recovering' from initially high levels of virus titer in the t issue to levels below detection with ELISA.