The objective of this study was to determine relative importance of gene effects for PBNV incidence and PBNV severity evaluated at 30, 40, 50 and 60 days after planting. Eight generations of three crosses involved three parental lines were evaluated for disease incidence (percentage of infected plants) and disease severity under natural occurrence of PBNV infection in a randomized complete block design with six replications. Evaluations were carried out at 30, 40, 50 and 60 Days After Planting (DAP). The analysis followed Hayman's model and Gamble's notations were used to describe parameters of gene effects. Joint scaling test was used to determine adequacy of the model. Additive gene effect was the most important contribution to genetic variation in generation means for both disease incidence and disease severity in the cross ICGV 86388 x IC 10. Selection for lower disease incidence and disease severity in this cross is promising. Additive gene effect and additive x additive epistatic gene effect were also important but in lower magnitude in the cross ICGV 86388 x KK 60-1 for disease incidence at 60 DAP. The presence of significant dominance gene effect in this cross for disease incidence might hinder the progress from selection. The consistent and significant additive gene effect for disease severity might provide a better selection strategy. Additive gene effect was significant for disease incidence only in the cross IC 10 x KK 60-1 at 60 DAP. Additive x dominance epistatic gene effect was also significant at 40 DAP, but no genetic parameter was significant for disease severity. This cross is considered less promising.