The development of genetically improved red tilapia lines through the backcross breeding of two Oreochromis niloticus strains

Abstract

In order to develop a crossbred of Oreochromis niloticus with a high growth rate and coloration, a backcross breeding program was developed using Red-Stirling and Chitralada strains with 50%, 75%, and 87.5% of genic proportion to Chitralada. Seven genetic groups were obtained from Chitralada (C) and Red-Stirling (R): the hybrids F1, fish-female Red-Stirling × fish-male Chitralada (RC), and its reciprocal (CR), and the backcross breeding (BB1), fish-female CR × fish-male Chitralada (CR × C), and its reciprocal (C × CR) and BB2 [C(C × CR)]. Growth curves were adjusted using an exponential model for females and males. The curves show a distinct difference among genetic groups and between genders based on the backcross breddingapproach. The best ranking for red females was observed in BB1 [C × (CR)]. The gain observed is due to the action of a genetic additive effect of Chitralada (42.90 g), a maternal effect of Chitralada (41.48 g), and a non-additive effect, which is attributed to paternal heterosis (11.41 g). While the best ranking for red males was found in BB2, The observed gain may be attributed to an additive genetic effect of Chitralada (74.04 g) and maternal effect of Chitralada (57.68 g). Survival among females was average. Among males, a higher mortality in the Red-Stirling group was observed compared to the other groups. These results indicate that the backcross breeding program can be used to develop genetic lines of red tilapia for further genetic breeding programs mainly exploring paternal heterosis to produce dams.