Tomato Spotted Wilt Virus in Papaya and Detection of the Virus by ELISA

Abstract

A new disease of papaya caused by the tomato spotted wilt virus was observed in Hawaii [USA] on the island of Kauai in 1962. Disease symptoms on plants 2-3 mo old were spotting, chlorosis, and necrosis of the top leaves; water-soaked lesions of the petioles and stems; and crooks at the stem apexes. These young plants were usually killed, although some survived, producing healthy axillary shoots. Fruit-bearing infected plants produced deformed fruit, which at ripening, had prominent green rings on a yellow background. The disease was invariably associated with orchards that had numerous Emilia fosbergii (formerly E. sonchifolia) weeds infected with tomato spotted wilt virus (TSWV). The host range and physical properties of the papaya virus were identical to those of TSWV. The disease was reproduced by mechanically inoculating papaya seedlings with leaf extracts from infected papaya plants and from TSWV-infected lettuce. The lettuce isolate of TSWV was purified and antiserum produced to it. The antiserum was effective in detecting TSWV in leaf tissue by sodium dodecyl sulfate agar gel immunodiffusion tests and by direct and indirect ELISA (enzyme-linked immunosorbent assay). Serology proved useful in diagnosing TSWV infections in plants.