Genetic analysis was carried out in six generations (P1, P2, F1, F2, B1 and B2) of four onion crosses viz., PBR 138 x AN 187, PBR 139 x AN 184, PBR 139 x AP 195 and PBR 140 x AN 184 to study the inheritance of resistance to purple blotch disease both under natural epiphytatic condition and artificial inoculation method . Results on gene effects under natural disease condition revealed that both additive (d and i) and non-additive (h, j and l) gene action were significantly operative in all the crosses. However, the interaction dominance x dominance and dominance type of gene action was predominant. Duplicate type of epistasis was observed in all the crosses. Reciprocal recurrent selection breeding method seems to be the best method  to improve this trait as it utilizes all the gene effects simultaneously. Heterosis breeding is also an option to exploit dominance and dominance x dominance type of interaction to develop hybrids.