Effect of inbreeding on growth, SURVIVAL, DISEASE RESISTANCE AND genetic diversity of Oreochromis niloticus based on the full-sibling inbreeding families IN TILAPIA HATCHERIES IN EGYPT

This study aimed to investigate the effects of inbreeding on growth, survival, disease resistance and genetic diversity in the Nile tilapia, Oreochromis niloticus. Full-sibling inbred groups were established at five levels of inbreeding coefficient (F values of 0.271, 0.388, 0.490, 0.581 and 0.687). The growth, survival, disease resistance and genetic diversity of the control tilapia group (F ≈ 0) differed significantly from each of the inbred tilapia groups at four ages (60, 90, 120 and 180 days old). Significant inbreeding depression was found in all inbred groups (P < 0.05) and this ranged from −2.67 to −23.83 %, and there was a tendency for inbreeding depression to increase with increasing F value and age. At 180 days old, inbreeding depression was 6.98, 16.20, 18.99 23.77 and 24.45 % for the F values of 0.271, 0.388, 0.490, 0.581 and 0.687, respectively. Moreover, there was a tendency for inbreeding depression of body weight to increase with the increasing age; for example, inbreeding depression was greater at 180 days compared to that of 60, 90 and 120 days old. Inbreeding depression per 10 % increase in the inbreeding coefficient value ranged from −1.05 to −4.03 %. The genetic parameter (PIC, n_a, a_e, Ho and He values) decreases with the increasing level of inbreeding. The greatest changes in the various genetic results are between the control group and the group (F = 0.271), thereafter the rate of loss slows. This study demonstrates that inbreeding has negative effects on growth, survival, disease resistance and genetic diversity in Oreochromis niloticus, thus strengthening the case to maximize genetic diversity in tilapia hatcheries in Egypt.

Keywords: Oreochromis niloticus, Inbreeding, Growth, Survival, Genetic diversity