Genome structure and variability of Fijiviruses

Abstract

The Fijivirus [Fiji disease virus, rice black-streaked dwarf virus (RBSDV), maize rough dwarf virus (MRDV), and pangola stunt virus (PaSV), the mal de Rio Cuarto virus (MRCV) strain of MRDV, and oat sterile dwarf virus] are distributed worldwide except for north America, and some of them cause serious disease. However, their genomes have not been extensively studied, and limited molecular data are available only for RBSDV, MRDV, PaSV and MRCV. ALl Fijiviruses have 10 segments, with an aggregate genome size larger than in other plant reovirus genera. All viruses analysed possess the same terminal conserved sequences, which differ from those of the phytoreoviruses and oryzaviruses. There are also sequence-specific inverted repeats adjacent to the terminal sequence. With MRDV and RBSDV, at least two of the segments are bicistronic. Homology studies suggest that MRDV and RBSDV, although known as separate viruses, should be considered as geographical races of the same virus. In contrast, limited data suggest that PaSV and MRCV are less close to each other and to MRDV/RBSDV. Electropherotyping has revealed variation among field isolates, with RBSDV, MRDV and MRCV.