Review on Barely Yellow Dwarf Viruses

Barley yellow dwarf virus (BYDV) is distributed worldwide, and infects most cereals and grasses. It is a phloem-restricted pathogen, causing yellowing, reddening, and brittleness of leaves, dwarfing, and reduction in size and number of ears and grains. BYDV is a luteovirus with small isometric particles containing an ssRNA genome, and is transmitted persistently by more than 20 aphid species. Five virus isolates have been distinguished and divided into two subgroups on the basis of cytopathology and serology. Recent serological evidence also indicates that BYDV isolates are related to other luteoviruses, suggesting that a continuous, over lapping range of viruses may be implicated in the barley yellow dwarf syndrome. Until future research clarifies this point, the term BYDV continues to be used to indicate the agent(s) involved. Perennial wild or cultivated grasses constitute a large and permanent virus pool. Primary and secondary virus spread depends on the aphid vector reproduction and flight which, in turn, are influenced by climatic conditions. Recent research on monitoring and control of aphid vectors and on development of resistant cereal cultivars has improved the prospect of minimizing losses from BYDV infections. Because of the economic importance of the BYDVs, more research is needed. The specific locations and timing of virus outbreaks, and the particular causal isolates, need to be monitored. This is will allow breeders to decide which BYDV isolate to target with transgenic resistance i