Effectiveness of DArTseq markers application in genetic diversity and population structure of indigenous chickens in Eastern Province of Rwanda.

BACKGROUND: The application of biotechnologies which make use of genetic markers in chicken breeding is developing rapidly. Diversity Array Technology (DArT) is one of the current Genotyping-By-Sequencing techniques allowing the discovery of whole genome sequencing. In livestock, DArT has been applied in cattle, sheep, and horses. Currently, there is no study on the application of DArT markers in chickens. The aim was to study the effectiveness of DArTSeq markers in the genetic diversity and population structure of indigenous chickens (IC) and SASSO in the Eastern Province of Rwanda. METHODS: In total 87 blood samples were randomly collected from 37 males and 40 females of indigenous chickens and 10 females of SASSO chickens purposively selected from 5 sites located in two districts of the Eastern Province of Rwanda. Genotyping by Sequencing (GBS) using DArTseq technology was employed. This involved the complexity reduction method through digestion of genomic DNA and ligation of barcoded adapters followed by PCR amplification of adapter-ligated fragments. RESULTS: From 45,677 DArTseq SNPs and 25,444 SilicoDArTs generated, only 8,715 and 6,817 respectively remained for further analysis after quality control. The average call rates observed, 0.99 and 0.98 for DArTseq SNPs and SilicoDArTs respectively were quite similar. The polymorphic information content (PIC) from SilicoDArTs (0.33) was higher than that from DArTseq SNPs (0.22). DArTseq SNPs and SilicoDArTs had 34.4% and 34% of the loci respectively mapped on chromosome 1. DArTseq SNPs revealed distance averages of 0.17 and 0.15 within IC and SASSO chickens respectively while the respective averages observed with SilicoDArTs were 0.42 and 0.36. The average genetic distance between IC and SASSO chickens was moderate for SilicoDArTs (0.120) compared to that of DArTseq SNPs (0.048). The PCoA and population structure clustered the chicken samples into two subpopulations (1 and 2); 1 is composed of IC and 2 by SASSO chickens. An admixture was observed in subpopulation 2 with 12 chickens from subpopulation 1. CONCLUSIONS: The application of DArTseq markers have been proven to be effective and efficient for genetic relationship between IC and separated IC from exotic breed used which indicate their suitability in genomic studies. However, further studies using all chicken genetic resources available and large big sample sizes are required.

Phenotypic characterization and analysis of genetic diversity between commercial crossbred and indigenous chickens from three different agro-ecological zones using DArT-Seq technology.

Indigenous and were used to study genetic diversity and population structure analyses. Polymorphism information content (PIC) values ranged from 0.0 to 0.5, with 21,285 SNP markers (35%) being in the lowest PIC value range (0 to 0.15) while 13,511 (commercial chickens have developed unique adaptations to their environments, which may include nutrition, pathogens, and thermal stress. Besides, environmental pressures and artificial selection have generated significant genome-wide divergence in chickens, as those selection pressures contribute a considerable evolutionary force to phenotypic and genotypic differentiation. Herein, we determined genomic diversity of indigenous chickens from semi-deciduous rainforest (SDR), coastal savannah (CS) and Guinea savannah (GS) agro-ecological zones (AEZs) in Ghana and commercial crossbreds (CC) reared at the Kwame Nkrumah University of Science and Technology (KNUST). We generated SNP markers from 82 chickens (62 indigenous chicken ecotypes and 26 commercial crossbred ecotype) using DArT-Seq technology. A total of 85,396 SNP markers were generated and after filtering the data, 58,353 markers 21%) were in the highest PIC value range (0.45 to 0.50). The CC were more genetically diverse than the indigenous birds, with the highest expected heterozygosity value of 0.220. Between the commercial crossbreds population and the indigenous ecotypes, pairwise FST values were estimated to be 0.105 between CS, 0.096 between SDF, and 0.133 between GS. Furthermore, PCA analysis showed that the CC, SDF and GS chickens clustered together and are genetically distant from the commercial crossbred. We herein show that chickens from the AEZs studied can be considered as one population. However, due the abundance of agro-byproducts in the SDR compared to the CS and GS, chickens from the SDR AEZ had better growth compared to their counterparts. It is suggested that the genetic diversity within the local ecotypes could form the basis for genetic improvement.

A comparative study of population structure and genetic diversity of commercial and indigenous chickens from different agro-ecological zones in Ghana using SilicoDArT and SNP markers.

Chicken production, both in the local and commercial sectors, contributes significantly to human livelihood and food security. Precise use of diverse genetic resources is primary in breeding programs. The study analyzed the genetic diversity and population structure of commercial chickens and indigenous chicken ecotypes from three different agro-ecological zones (Semi-Deciduous Rainforest Zone, Guinea Savannah, and Coastal Savannah) using SilicoDArT and SNP markers, utilizing whole-genome sequencing and phenotypic data. Phenotypic data were collected from 72 indigenous chicken ecotypes across the three AEZs, and 32 commercial birds kept at the Kwame Nkrumah University of Science and Technology (KNUST). DNA samples used for sequencing were obtained from 88 chickens (62 indigenous chicken ecotypes and 26 commercial chickens). A total of 54,995 SilicoDArT and 85,396 SNPs markers were generated from DArTseq genotyping. After filtering, 44,784 SilicoDArT and 58,353 SNP were used for genetic diversity and population structure analysis. Both markers showed high reproducibility and call rate. Polymorphic information content (PIC) values ranged from 0.00 to 0.50, while ≥ 50 % showed PIC values more than the median. Furthermore, we obtained FST values, Nei's genetic distance, dendrogram analysis, and principal component analysis (PCA) of commercial and indigenous chickens. The FST and Nei's genetic distance showed that there is high genetic diversity between the commercial chickens and the indigenous chicken ecotypes. However, there was low genetic diversity among the indigenous chicken ecotypes. The PCA analysis indicated a clear separation between the commercial and indigenous chicken ecotypes, while no clear separation was observed between the indigenous chicken ecotypes. The phenotypic data and the dendrogram indicated that naked and frizzle genes do not markedly alter the genetics of indigenous and commercial birds, and their influence on economic traits may be solely determined by the prevailing environmental conditions. The results indicate that there is high genetic differentiation between commercial and indigenous chickens based on SilicoDArT and SNP markers. The indigenous chickens from the agro-ecological zones have low genetic diversity and might have a common origin. Naked neck and frizzle genes do not markedly alter the genetic performance of birds in terms of economic traits. Therefore, the superiority of birds carrying these genes in economic traits may be solely due to environmental variation.