Poultry breeding has been one of the most impactful advances in the last 100 years. The role that improved global production of eggs and poultry meat have in reducing global hunger and food insecurity is difficult to overstate. The vast majority of these improvements have come from genetic selection for improved feed efficiency, along with streamlining of the overall production system, and better understanding of poultry nutrition. While the industrial approach to poultry production has created a highly consistent and dependable food source the world over, several problems threaten the long term sustainability of this model - including musculoskeletal and metabolic disorders, welfare concerns, and the need to adapt to a changing climate. In this chapter we trace the history of the poultry genetics enterprise, and how that model provides a platform for adapting to challenges of the future. We also assess the status of the latest technologies available for poultry breeding and discuss the scope of these technologies to counter emerging and future challenges.

Poultry genetics and breeding

Objective Complete mtDNA D-loop sequences of four Thai indigenous chicken varieties, including Pra-dhu-hang-dam (PD), Leung-hang-khao (LK), Chee (CH), and Dang (DA) were explored for genetic diversity and relationships with their potential ancestor and possible associates to address chicken domestication in Thailand. Methods A total of 220 complete mtDNA D-loop sequences of the four Thai indigenous chicken varieties were obtained by Sanger direct sequencing of polymerase chain reaction amplicons of 1,231 to 1,232 base pair in size. A neighbor-joining dendrogram was constructed with reference complete mtDNA D-loop sequences of Red Junglefowl (RJF) and those different chicken breeds available on National Center for Biotechnology Information database. Genetic diversity indices and neutrality test by Tajima's D test were performed. Genetic differences both within and among populations were estimated using analysis of molecular variance (AMOVA). Pairwise fixation index (FST) was conducted to evaluated genetic relationships between these varieties. Results Twenty-three identified haplotypes were classified in six haplogroups (A-E and H) with the majority clustered in haplogroup A and B. Each variety was in multiple haplogroups with haplogroups A, B, D, and E being shared by all studied varieties. The averaged haplotype and nucleotide diversities were, respectively 0.8607 and 0.00579 with non-significant Tajima's D values being observed in all populations. Haplogroup distribution was closely related to that of RJF particularly Gallus gallus gallus (G. g. gallus) and G. g. spadiceus. As denoted by AMOVA, the mean diversity was mostly due to within-population variation (90.53%) while between-population variation (9.47%) accounted for much less. By pairwise FST, LK was most closely related to DA (FST = 0.00879) while DA was farthest from CH (FST = 0.24882). Conclusion All 4 Thai indigenous chickens are in close relationship with their potential ancestor, the RJF. A contribution of shared, multiple maternal lineages was in the nature of these varieties, which have been domesticated under neutral selection.

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Genetic diversity analysis of Thai indigenous chickens based on complete sequences of mitochondrial DNA D-loop region.

The Jiangxi Province of China has numerous native domestic chicken breeds, including some black skin breeds. The genetic diversity of Jiangxi native chickens is largely unknown, and specifically, the genetic contribution of the grey junglefowl to black skin chickens is not well understood. To address these questions, the complete D-loop region of the mitochondrial DNA (mtDNA) and beta-carotene dioxygenase 2(BCDO2)gene was sequenced in a total of 209 chickens representing seven Jiangxi native breeds. Thirty-one polymorphic sites were identified across the complete mtDNA D-loop region sequence. Twenty-three haplotypes were observed in the seven breeds, which belonged to four distinct mitochondrial clades (A, B, C and E). Clade A and B were dominant in the chickens with a frequency of approximately 67.9%. There were five SNPs that defined two haplotypes, W and Y in BCDO2. Four breeds had one haplotype and three breeds had two. We conclude that Jiangxi native chicken breeds have relatively low genetic diversity and likely share four common maternal lineages from two different maternal ancestors of junglefowl. Furthermore, some Jiangxi chicken populations may have been mixed with chickens with exotic lineage. Further research should be established to protect these domestic chicken resources.

/pdf/the-genetic-diversity-of-chicken-breeds-from-jiangxi-wzfzk99q2d.pdf

The genetic diversity of chicken breeds from Jiangxi, assessed with BCDO2 and the complete mitochondrial DNA D-loop region

Nandan-Yao chicken is a Chinese native chicken with lower fat deposition and better meat quality. Fat deposition is a quite complex and important economic trait. However, its molecular mechanism is still unknown in chickens. In the current study, Nandan-Yao chicken was divided into two groups based on the rate of abdominal fat at 120 days old, namely the high-fat group and low-fat group. The total RNAs were isolated and sequenced by RNA sequencing (RNA-seq). After quality control, we gained 1222, 902, 784, 624, and 736 differentially expressed genes (DEGs) in abdominal fat, back skin, liver, pectoral muscle, and leg muscle, respectively. Analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) showed that significantly enriched GO term and KEGG signaling pathway mainly involved cytosolic ribosome, growth development, PPAR signaling pathway, Wnt signaling pathway, and linoleic acid metabolism in abdominal fat, back skin, and liver. While in pectoral muscle and leg muscle, it is mainly enriched in phosphatidylinositol signaling system, adrenergic signaling in cardiomyocytes, cytosolic ribosome, and cytosolic part. Sixteen genes were differentially expressed in all five tissues. Among them, PLA2G4A and RPS4Y1 might be the key regulators for fat deposition in Nandan-Yao chicken. The protein-protein interaction (PPI) network analysis of DEGs showed that PCK1 was the most notable genes. The findings in the current study will help to understand the regulation mechanism of abdominal fat and intramuscular fat in Nandan-Yao chicken and provide a theoretical basis for Chinese local chicken breeding.

Transcriptome landscapes of differentially expressed genes related to fat deposits in Nandan-Yao chicken

Deep-sea organisms survive in an extremely harsh environment. There must be some genetic adaptation mechanisms for them. We systematically characterized and compared the complete mitochondrial genome (mitogenome) of a deep-sea crab (Chaceon granulates) with those of shallow crabs. The mitogenome of the crab was 16 126 bp in length, and encoded 37 genes as most of a metazoan mitogenome, including 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 ribosomal RNA (rRNA) genes. The gene arrangement and orientation was conserved in the crabs. However, a unique mitogenome element regulator, the origin of light-strand replication (OL), was firstly predicted in the present crab mitogenome. In addition, further positive selection analysis showed that two residues (33S in ND3 and 502I in ND5) in C. granulates mitogenome were positively selected, indicated the selective evolution of the deep-sea crab. Therefore, the mitogenome of deep-sea C. granulates showed a unique OL element and positive selection. These special features would influence the mitochondrial energy metabolism, and be involved in the adaptation of deep-sea environment, such as oxygen deficits and low temperatures.

Comparative analysis of mitochondrial genome of a deep-sea crab Chaceon granulates reveals positive selection and novel genetic features

The domestic chicken (Gallus gallus domesticus) is an excellent model for genetic studies of phenotypic diversity. The Guangxi Region of China possesses several native chicken breeds displaying a broad range of phenotypes well adapted to the extreme hot-and-wet environments in the region. We thus evaluated the genetic diversity and relationships among six native chicken populations of the Guangxi region and also evaluated two commercial breeds (Arbor Acres and Roman chickens). We analyzed the sequences of the D-loop region of the mitochondrial DNA (mtDNA) and 18 microsatellite loci of 280 blood samples from six Guangxi native chicken breeds and from Arbor Acres and Roman chickens, and used the neighbor-joining method to construct the phylogenetic tree of these eight breeds. Our results showed that the genetic diversity of Guangxi native breeds was relatively rich. The phylogenetic tree using the unweighed pair-group method with arithmetic means (UPGAM) on microsatellite marks revealed two main clusters. Arbor Acres chicken and Roman chicken were in one cluster, while the Guangxi breeds were in the other cluster. Moreover, the UPGAM tree of Guangxi native breeds based on microsatellite loci was more consistent with the genesis, breeding history, differentiation and location than the mtDNA D-loop region. STRUCTURE analysis further confirmed the genetic structure of Guangxi native breeds in the Neighbor-Net dendrogram. The nomenclature of mtDNA sequence polymorphisms suggests that the Guangxi native chickens are distributed across four clades, but most of them are clustered in two main clades (B and E), with the other haplotypes within the clades A and C. The Guangxi native breeds revealed abundant genetic diversity not only on microsatellite loci but also on mtDNA D-loop region, and contained multiple maternal lineages, including one from China and another from Europe or the Middle East.

Genetic diversity of Guangxi chicken breeds assessed with microsatellites and the mitochondrial DNA D-loop region

The invention discloses a screening method of chicken breeding materials, belonging to the field of agricultural livestock and poultry breeding. The screening method of chicken breeding materials comprises the following steps: 1) extracting genomic DNA; 2) performing microsatellite mark and PCR reaction; 3) performing mtDNA PCR reaction and sequencing; 4) performing statistical analysis; and 5) selecting breeding material. The invention adopts molecular biotechnology to analyze genetic diversity and genetic distance of breeding material, selects individuals with rich genetic diversity as breeding material, ensures rich genetic information, reduces blindness and risk of breeding, reduces breeding time, improves breeding efficiency and reduces breeding cost.

Screening method of chicken breeding materials

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Genetic diversity of Guangxi chicken breeds assessed with microsatellites and the mitochondrial DNA D-loop region

Screening method of chicken breeding materials