Polymorphism detection of promoter region of IFN-$$\gamma $$ and IL-2 genes and their association with productive traits in Mazandaran native breeder fowls

To identify polymorphism in interferon gamma (IFN-\(\upgamma \)) and interleukin-2 (IL-2) genes, blood samples were collected from 380 breeder hens of the Mazandaran native fowls breeding station. DNA extraction was performed through a modified salting-out method and fragments of 670 and 659 bp from the promoter regions of IFN-\(\upgamma \) and IL-2 genes were amplified by using specific primers, respectively. Following genotyping in the IFN-\(\upgamma \) gene using the Tsp509I restriction enzyme, two alleles of A and G with the frequencies of 0.55 and 0.45 and three genotypes of AA, AG and GG were observed with the frequencies of 0.32, 0.46 and 0.22, respectively. For the IL-2 gene, two alleles of A and G were also detected using the MnlI restriction enzyme with the frequencies of 0.58 and 0.42 and three genotypes of AA, AG and GG with the frequencies of 0.33, 0.50 and 0.17, respectively. Statistical analysis revealed significant associations between IL-2 gene single-nucleotide polymorphism and productive traits including the average egg weight (EW) at 345–375 days of age, egg number (EN) at 345–375 days of age and body weight (BW) at 8 weeks of age traits (\(P{<}0.05\)). Further, in a mean comparison analysis, there were also significant differences between different genotypes of the IL-2 gene in average EW at 28 and 30 weeks of age, in which AG genotypes showed higher performance. Additionally, for the IFN-\(\upgamma \) gene, a significant difference was found between the genotypes in average EW at 28 weeks of age trait. Therefore, it can be concluded that the above-mentioned polymorphisms could be considered as the pivotal genetic makers to improve Mazandaran native fowl breeding programmes to achieve the optimum performance in productive traits more efficiently.