Tobacco streak virus (tobacco streak).
Abstract TSV is prevalent in south-eastern Brazil, and can limit yields of soyabeans in some years (Costa and Carvalho, 1961). Epidemics of soyabean bud blight, caused by TSV, were monitored in two soyabean cultivars sown on seven different dates in 1987-88 in Arapoti County, Parana. The highest final level of disease incidence was 60% in 1987 and 90% in 1988 (Almeida et al., 1994a). Brazilian bud blight is also a serious disease in the Santa Fe province of Argentina (Laguna et al., 1988). It occurs in the USA (Fagbenle and Ford, 1970; Kaiser et al., 1982; Sherwood and Jackson, 1985) but is of no economic significance on soyabeans because conditions are not conducive to the development of the problem. TSV presents a major problem in sunflower production in the Indian subcontinent as severe necrosis symptoms may lead to major losses (Bhat et al., 2002).