Alleles and genotype frequencies of transferrin in common carp (Cyprinus carpio) in Southern Iraq

Common carp (Cyprinus carpio) is widely found across Asia and Europe. The species is popular for its tolerance to physiological and environmental stresses. Alleles encoding transferrin (Tf) in common carp have been studied for their role in identification of tolerant type and to investigate breeding pattern. However, the data about Tf alleles of common carp from Iraq has been described less frequently. Therefore, this study aimed to determine the frequencies of various Tf alleles in 142 common carp specimens collected from 32 different locations. The alleles were detected through SDS PAGE and their abundance was correlated with physicochemical parameters of the sampled water. Our results indicated a degree of genetic polymorphism with the presence of C, D, F and G alleles. The allele DD was found to be the most prevalent followed by FF while other alleles were present in low numbers. Hardy-Weinberg equilibrium showed a marked difference from observed values with a high x2 value (251.57; p < 0.001), suggesting that selective forces, population structuring or environmental factors may have influenced Tf genotype distribution within the study population. The low observed heterozygosity than the expected heterozygosity and Shannon diversity index reflected substantial allelic variation. The allelic dominance was also correlated with the water temperature and iron concentration. Hence, population structuring of common carp may be linked more to physicochemical variability than to random mating. The role of Tf in iron metabolism and immune system necessitates further investigations to support aquafarming and to maintain a sustainable supply of animal protein.