Genetic evaluation of growth and survival at 6 weeks old fry of Egyptian Nile Tilapia (Oreochromis niloticus) between improved Abbassa and commercial Manzala strains in a diallel crossing

This study aims to evaluate growth performance and estimate additive genetic, heterosis, and general reciprocal effects for body weight, body length, condition factor, and survival of Nile tilapia (Oreochromis niloticus) fry at 6 weeks old after hatching using a complete diallel cross between the genetically improved “Abbassa” strain(A) and a commercially available strain Manzala(M). Body weight and total body length were observed significantly (P <0.001) higher in MmAf and AmMf crosses (2.87g & 5.55 cm; 2.78g & 5.33cm, respectively). The straight-bred AmAf weight and length were 2.64g, 5.18cm, respectively while the straightbred MmMf showed the lowest growth parameters 2.42g and 5.04cm,respectively.Condition factor of AmAf, AmMf, and MmMf genotypes (1.89, 1.85, and 1.81 respectively) didn’t differ significantly whereas the MmAf cross showed a significantly lower condition factor 1.67. The survival of the straight-bred AmAf was 0.98,which significantly (P <0.001) higher than AmMf, MmAf, and MmMf genotypes. Abbassa strain showed 5, 2.1, and 10% additive genetic effect above the overall mean in body weight, survival, and condition factor respectively. Heterosis estimates were positive and relatively high 11.7% and 6.2% for body weight and total body length while a negative heterosis estimates were observed for the condition factor and survival, being -6.7% and -2.6% respectively. Reciprocal effect was significant (P <0.001) for total body length and condition factor. The results of the current study suggest that body weight and total body length of the Nile tilapia fry at 6 weeks old after hatching could be improved through crossing schemes exploiting the heterosis effect however the crossing did not show any improvement in survival.