The development of genetically improved red tilapia lines through the backcross breeding of two Oreochromis niloticus strains Aline de Assis Lago a , Tiago Teruel Rezende b , Marco Aurélio Dessimoni Dias a , Rilke Tadeu Fonseca de Freitas a , Alexandre Wagner Silva Hilsdorf a,c, ⁎ a Department of Animal Sciences, Federal University of Lavras, Lavras, Minas Gerais, Brazil b Department of Agriculture, Federal University of Lavras, Minas Gerais, Brazil c Unit of Biotechnology, University of Mogi das Cruzes, Mogi das Cruzes, São Paulo, Brazil abstract article info Article history: Received 5 August 2015 Received in revised form 28 June 2016 Accepted 29 June 2016 Available online xxxx In order to develop a crossbred of Oreochromis niloticus with a high growth rate and coloration, a backcross breed- ing program was developed using Red-Stirling and Chitralada strains with 50%, 75%, and 87.5% of genic propor- tion to Chitralada. Seven genetic groups were obtained from Chitralada (C) and Red-Stirling (R): the hybrids F 1 , 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 het- erosis (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 fe- males 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. Statement of relevance: The present study proposes a breeding methodology based in robust statistical analysis to develop genetically lines of red tilapia. © 2016 Published by Elsevier B.V. Keywords: Heterosis Quantitative genetics Recurrent backcross Gene introgression Breeding program 1. Introduction The per capita global consumption of fish has increased from 9.9 kg in 1960 to 19.2 kg in 2012 (FAO, 2014). China remains the world's larg- est producer of aquaculture fish and Brazil ranks 12th in aquaculture production (707.461 tons in 2012) (FAO, 2014). Aquaculture is the sec- tor of food production with the fastest growth rate in Brazil, with an in- crease in 61.4% between 2009 and 2011. The Nile tilapia, Oreochromis niloticus, represents a species with the highest production (169,306 tons in 2013), corresponding to 43% of the total of inland aquaculture production (IBGE, 2013). Considering this recent growth and intensifi- cation in aquaculture production, there is a need for new technologies and higher performance strains to make a more efficient and sustain- able supply chain. Red tilapia was first discovered in Taiwan in the 1960s (Kuo and Tsay, 1984; Kuo, 1988). Since then, different strains of red tilapia have been commercially grown and many hybrids have been created from different species, predominantly Oreochromis mossambicus and O. niloticus (Koren et al., 1994; Romana-Eguia et al., 2004). Red-Stirling is a red variety of O. niloticus that produces all-red progeny due to a single autosomal dominant gene (McAndrew et al., 1988; Hussain, 1994). Red tilapia sales have grown in some markets due to a greater acceptance of red varieties, as well as the recognition of the value it adds to the final product (Josupeit, 2005; Hamzah et al., 2008; Thodesen et al., 2013). Selection programs and interspecific crossbreeding have been devel- oped in order to improve the production efficiency of red tilapia (Behrends et al., 1990; Thodesen et al., 2013). Methods based on back- cross breeding have aimed to increase the genetic variety of higher per- formance strains and to maintain phenotypes of interest (which have not been reported in the literature), with regard to the development Aquaculture xxx (2016) xxx–xxx ⁎ Corresponding author at: Universidade de Mogi das Cruzes, Núcleo Integrado de Biotecnologia, Av. Dr. Cândido Xavier de Almeida Souza, 200, 08780-911 Mogi das Cruzes, SP, Brazil. E-mail address: wagner@umc.br (A.W.S. Hilsdorf). AQUA-632217; No of Pages 6 http://dx.doi.org/10.1016/j.aquaculture.2016.06.042 0044-8486/© 2016 Published by Elsevier B.V. Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Please cite this article as: Lago, A.A., et al., The development of genetically improved red tilapia lines through the backcross breeding of two Oreochromis niloticus strains, Aquaculture (2016), http://dx.doi.org/10.1016/j.aquaculture.2016.06.042