Resistance to tomato spotted wilt virus in transgenic tomato varieties

Tomato spotted wilt virus (TSWV) is a thrips transmitted plant virus which infects more than 650 plant species belonging to different botanical families (Peters et al. 1990, Goldbach, Peters 1994). Tomato appears to be one of the most vulnerable to TSWV economically important plant species due to its prolonged cultivation period in the greenhouse and the monoculture field cultivation. TSWV is among the most important viral diseases affecting tomato and causing significant economic losses. The infected plants are stunted and with reduced yield, the fruits are blemished with necrotic and chlorotic ringspots, making them unmarketable. Sources of genetic resistance have been reported to exist in genus Lycopersicon and tomato cultivars descending from such accessions have been described to be resistant to TSWV and not isolate specific (Stevens et al., 1994; Boitieaux, Giordano 1993). However in the field, in plants carrying a resistance gene from L. peruvianum, the virus still accumulates resulting in the development of disease symptoms on the fruit (Ultzen et al. 1995; Rosello et al. 1996). Efficient engineered pathogen derived TSWV resistance in tomato is reported by Ultzen et al. (1995) and Kim et al.(1994).