Differential resistance to edwardsiellosis in rohu (Labeo rohita) families selected previously for higher growth and/or aeromoniasis-resistance.

Selection in fish for disease resistance is one of the most useful approaches to solve disease problems. Genetic variation in resistance to edwardsiellosis in fullsib families of rohu, Labeo rohita was investigated in the present study. A large variation in the susceptibility pattern (0 to 94.74 percent survival) against Edwardsiella tarda challenge was observed among 57 families. Additive genetic variation showed a heritability of 0.38 ± 0.08 across the year-class survival. The apparent resistant families showed more delayed mortality than the apparent susceptible ones. The cross-protection provided by aeromoniasis-resistant lines of rohu to edwardsiellosis was also studied to evaluate the possibility of selection for both diseases simultaneously. Challenge of F1-generation aeromoniasis-resistant and -susceptible lines with E. tarda showed significant difference in survival between the lines with higher percent survival in resistant line. This study suggests that direct selection method may be used reliably in selection programs and selection for multiple diseases simultaneously can be considered for rohu.