Genotype responsive growth performance and salinity tolerance of tilapia hybrid (Oreochromis niloticus × O. mossambicus)

Abstract

The unstable salinity level in the coast forced the aquaculture practice in saline conditions. The inherent genetic qualities of tilapia, one of the major contributors to aquaculture production worldwide, help domesticate easily in a diverse set of aquatic conditions. A set of pre-selected (genotypes of a specific marker) males (m) and females (f) from both Oreochromis niloticus (N) and O. mossambicus (M) were kept inside hapas with a 1:1 ratio for interspecific hybridization, O. niloticus × O. mossambicus. Four progenies of the interspecific hybrid, one of traditional intraspecific and one more of the unknown intraspecific genotypic progenies (F1) were considered to detect the superiority of growth and survival induced by salinity in relation to allelic sensitivity. Collected progenies from different cross combinations with two replications each were reared for comparing growth inside hapa within an earthen pond for 60 days. Survival probabilities were tested under salinity stress (gradual incline up to 30 ppt and then decline to freshwater condition by 22 days) inside plastic drums. Stocking similarities were followed and weight-defined feeding was applied. Similar growth was observed between intraspecific Nf × Nm offsprings and interspecific Mf × Nm progenies but the reciprocal of the interspecific cross (Nf × Mm) progenies demonstrated an inferior growth rate in the freshwater earthen pond (inside hapa). Among interspecific crosses: F1 hybrids of female M homozygous for the short allele (PrlLK_254/254) and male N homozygous for the long allele (PrlLK_281/281) showed superior growth performance while the F1 hybrid between female M homozygous for short (PrlLK_254/254) and male N homozygous for short allele (PrlLK_254/254) showed menial. Moreover, the F1 progenies produced by crossing homozygous short females M with homozygous long and heterozygous (long/short) showed superior growth compared to those produced by crossing with homozygous short males of N. On the other hand, F1 progeny produced by crossing homozygous short males of M with females of N (homozygous long) showed a comparatively inferior growth rate. Mf_254/254 × Nm_281/254 and Mf_254/254 × Nm_281/281 offspring displayed interaction effects with other groups. No mortality was recorded until 15 ppt and during the declining phase from 30 ppt to freshwater condition. By different cross types and sexes, the survival probabilities were not significantly different. Interspecific hybrids with homozygous alleles (either long or short) showed total survival probability whereas the heterozygous parent demonstrated the most awful survivability with significant dissimilarity (p = 0.04). Because the shorter allele is responsible for better survival inside higher salinity and the longer is for higher growth in freshwater; the selection of the parental group depending on marker assistant allelic segregation could propose a pertinent protocol in the coastal region.