Biological and genetic diversity of plasmodiophorid-transmitted viruses and their vectors

About 20 species of viruses belonging to five genera, Benyvirus, Furovirus, Pecluvirus, Pomovirus and Bymovirus, are known to be transmitted by plasmodiophorids. These viruses have all positive-sense, single-stranded RNA genomes that consist of two to five RNA components. Three species of plasmodiophorids are recognized as vectors: Polymyxa graminis, P. betae, and Spongospora subterranea. The viruses can survive in soil within the long-lived resting spores of the vector. There are biological and genetic variations in both virus and vector species. Many of the viruses are causal agents of important diseases in major crops such as rice, wheat, barley, rye, sugar beet, potato, and groundnut. Control is dependent on the development of resistant cultivars. During the last half century, several virus diseases have rapidly spread worldwide. For six major virus diseases, we address their geographical distribution, diversity, and genetic resistance.