Molecular biology of tenuiviruses, a remarkable group of plant viruses

Introduction. The tenuiviruses are a most unusual type of virus about which little was known until recently. They were officially recognized as a plant virus group in 1983 (reviewed in Gingery, 1988). They are described in the Fifth Report of the International Committee on Taxonomy of Viruses as non-enveloped plant viruses, with possibly a negative ssRNA genome (Francki et al., 1991). Five viruses belong to this group, the type member rice stripe virus (RSV) first discovered in Japan in the 1890s, followed by maize stripe virus (MStV) in Mauritius in 1929, rice hoja blanca virus (RHBV) in Colombia in 1935, European wheat striate mosaic virus (EWSMV) in England in 1956, and rice grassy stunt virus (RGSV) in the Philippines in 1963 (reviewed in Gingery, 1988). Epidemics of RSV and RHBV cause important yield losses in rice-growing areas of Asia and the former U.S.S.R. (Toriyama, 1983), and of tropical America (Morales & Niessen, 1985) respectively.