Polymorphism and genetic diversity of chicken growth hormone in selected chicken breeds in Nigeria

Abstract

The study was carried out to investigate polymorphism and genetic diversity of the chicken growth hormone gene of selected chicken breeds (Fulani ecotype, Noiler, FUNAAB Alpha broiler, Frizzled feathered, Cobb 500) in Nigeria. Genomic DNA was extracted from blood samples collected from 49 birds. Amplification of specific DNA fragments at intron 3 of the cGH gene yielded a product size of 715bp and this was used to analyze for polymorphism using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCRRFLP) technique. The extracted DNA was amplified using PCR and the gene sequenced. The sequenced data was used to evaluate genetic diversity and to carry out phylogenetic analysis. The banding patterns of the gene investigated, revealed the occurrence of three RFLP variants: TT, CT and CC, with genotype frequencies of 0.449, 0.245 and 0.306, respectively. The allele frequencies of the T and C alleles were 0.469 and 0.531, respectively indicating that the C allele was predominant. Chi-square test revealed that the chicken population investigated was in Hardy-Weinberg equilibrium. The mean number of alleles (Na), mean number of effective alleles (Ne), mean Shannon information index (I), and mean observed heterozygosity (Ho) were 2.000±0.000, 1.956±0.014, 0.682±0.004, 0.449±0.067, reapectively. Also, the mean expected heterozygosity (He), mean unbiased expected heterozygosity (uHe), mean fixation index (F), and % polymorphic locus were 0.489±0.004, 0.516±0.004, 0.083±0.138 and 100%, respectively. The gene flow (Nm) for all the population was 13.141. Results of analysis of molecular variance showed that the percentage of molecular variance among and within individuals was 13 and 87%, respectively. Phylogenetic analysis divided the five chickens into two broad groups; Noiler and the frizzled feathered occupied one cluster, while the Fulani ecotype, FUNAAB Alpha and Cobb 500 occupied the other cluster. It was concluded that great genetic diversity exists in the chicken breeds which could be exploited for further improvement.