Monogamous hybridization of Nile tilapia (Oreochromis niloticus) with Mozambique tilapia (O. mossambicus) results in unprecedented all-female F1 hybrid

Tilapiine breeding success is season-dependent, with very rare exceptions. The female (f) to male (m) ratio differences showed significant variations in fruitful breeding. Furthermore, the female-to-male ratio in any hybridization protocol involving reciprocal crosses may be the most influential factor in determining breeding seasonality. The innate genetic traits of tilapia, a prominent contributor to global aquaculture production, enable them to easily adapt to a wide range of aquatic environments, rendering them suitable for domestication. The study aimed to determine the breeding timeframe of Nile tilapia (Oreochromis niloticus, N) through interspecific monogamous/two-parent reciprocal crossing with Mozambique tilapia (O. mossambicus, M). Considering preselected genotypic characteristics by PrlLK microsatellite marker, different combinations of hybrid reciprocal crosses were performed in breeding hapa (3 × 3 × 3 cubic feet) inside an indoor plastered cemented tank and then in an outdoor earthen pond facility. Total 11 parental pairs were attempted to propagate inside a cemented tank with (9 pairs) and without (2 pairs) hapa during early April to mid-June. Unfortunately, the trials failed to produce any successful breeding within the schedule. Among those 11 pairs, 6 pairs were Nf × Mm and 5 pairs were Mf × Nm cross. In the earthen pond inside hapa, a total of 18 pairs were attempted where seven breeding successes were reported without demonstrating any dependency for hybridizations over cross types or genotypes and for individuals over sex or species. Successful breeding were reported from the month of May to November. There were few overlapping months of successful breeding for different grouping categories. During the successful breeding period, there were no successful outcomes in both August and October. An inadvertent all-female F1 generation was observed for Mf × Nm crosses, while the reciprocal cross Nf × Mm produced an F1 generation with a nearly 1:1 female to male ratio. The F1 sex ratios exhibited a significant reliance on parental genotypic combinations (p = 5.4e^-11). The success stories from different cross combinations would help to frame the breeding protocol for future research. More precisely, for arranging a breeding schedule in freshwater earthen ponds inside hapa for a monogamous/two-parent hybrid cross the study light a close insight.