Barley yellow dwarf (BYD) is the most economically important disease on cereal production worldwide.The causal virus actually includes several distinct virus species of the family Luteoviridae,that differ in the genomic structure and the specific aphid vector species.In Japan,the BYDV-PAV incidence on barley was reported in Niigata and in some other areas.However,during the field survey conducted on 2009 and 2010,CYDV-RPS genotype was prevalent on barley fields.