Virus yellows (VY) is an important disease of sugar beet, caused by some virus species transmitted by the polyphagous aphid Myzus persicae and others, which causes yellowing symptoms on the outer large leaves and reduced sugar yield. The VY prevalent in Japan was previously thought to be Beet Western Yellowing Virus (BWYV), which has been identified in the United States, but was recently named Beet Leaf Yellowing Virus (BLYV), a new species in the same genus (Polerovirus) as BWYV. In this study, we report the following three findings for the aim of efficient resistant breeding for BLYV. (1) Through four years of preliminary research, an assay was developed to estimate leaf yellowing caused by BLYV using an index (0: no symptoms – 3: overall yellowing) or the yellowing area ratio (%) calculated from digital camera images. (2) Using this assay, a two-year evaluation of 100 Japanese lines including USDA VY-resistant germplasm revealed that only the germplasm showed strong resistance to BLYV, suggesting that the mechanism of resistance to BWYV and BLYV may be common. (3) QTL analysis was performed from phenotype and genotype data of 144 F2:3 progenies developed by crossing susceptible and resistant parents for two years, and several common QTLs associated with the resistance were detected. DNA markers were developed to select for BLYV resistance based on the information. This research was supported by the research program on development of innovative technology grants (Grant Number: JPJ007097) from the Project of the Bio-oriented Technology Research Advancement Institution (BRAIN).