Mungbean yellow mosaic disease, transmitted by whitefly, is most damaging disease of mungbean in all of its growing areas. Genetic resistance is a viable and environment friendly solution, for which resistance source is prerequisite. Total 83 mungbean accessions were evaluated under protected and unprotected field conditions following split plot design. Infection % age and disease severity based scoring scales were compared for their discrimination potential for screening. Disease severity based scoring scale was found superior to infection % age based scale because it categorized genotypes into five groups while only two groups were generated by later. Infection % age ranged from 33.33 to 100% while disease severity index varied from 10 to 75%. Only one genotype (NM 6-68-2) was found resistant (D.I. 10%) while three accessions NM 57, NM 1-32-1, NCM 254-3 were highly susceptible. Disease severity showed maximum correlation with chlorophyll-a reduction followed by 100 seed weight. Path analysis revealed that direct effect of disease on yield reduction was negligible but it caused yield reduction via reduced harvest index and 100 seed weight. Resistance to MYMD is governed by two major genes with additive nature. There was variability in genetic components of different traits under both field conditions.