Genetic relationships In Philippine genetically-enhanced strains of farmed tilapia using mitochondrial DNA markers and gene expression of hsp70 and IL-1β in response to stress factors

The potential unknown effects of global warming and other stressful environmental conditions on fishes is pressing the need to clarify stress and immune mechanisms in cells that help fish survive changes in optimum environmental conditions. Comparison of the stress responses of the genetically enhanced farmed tilapia strains in the Philippines has not yet been studied molecularly. Moreover, the development of various genetically-enhanced tilapia through the years to meet the demands of tilapia production has brought about strains that are morphologically the same but perform differently. This study revealed the phylogenetic relationships of six Philippine genetically-enhanced tilapia strains, FaST, GET-EXCEL, iBEST, Red Tilapia-FAC, Red Tilapia-BFAR and GIFT, using the mitochondrial markers D-Loop and 16S rRNA. The findings of this study also demonstrate the response of closely related strains exposed to thermal stress and different densities through their expression of the stress-related gene, heat shock protein 70 and immune-related gene, Interleukin-1β. Genetic relationship results in this study indicate the hyperdivergence of the FaST strain based on D-Loop sequences. Gene expression studies show that temperature and density influence the expression of hsp70 and IL-1β. Analyses show that the FaST, GET-EXCEL, iBEST, Red Tilapia-FAC, Red Tilapia-BFAR perform the same and no differences were noted in terms of stress responses. The high water temperatures in the study which is reflective of global warming temperatures have shown that the enhanced strains can compromise via expression of stress- and immune-related genes hsp70 and IL-1β. All the strains demonstrate the adaptability and resiliency to thermal stress as well as density stress. Hence, these strains are assumed to be ‘climate smart’ and can withstand the pressures of changing global conditions