Year: 2013
Type: article
Abstract: Local breeds can be considered a part of the history of some human populations as well as important materials from a scientific point of view. The characterisation and inventory of animal genetic resources and routine monitoring of population for variability are fundamental to breed improvement strategies and programmes and for conservation programmes. Molecular genetics provide us with very remarkable tools to analyse the variation between and within breeds. Different approaches have been developed to understand the different aspects that contribute to breed differentiation. The thesis is made up in three contributes. The objective of the first part (Chapter 3) was to investigate genetic variation and to analyze population structure in two Italian breeds (Ancona and Livorno) as potential valuable genetic variability source. Blood samples from 131 individuals were collected and genotyped through a thirty microsatellites-based analysis. All the observed descriptive statistical indexes suggested a heterozygosity deficiency and an inbreeding level (mean observed heterozygosity = 0.46, mean expected heterozygosity = 0.53, FIS in Ancona and Livorno = 0.251 and 0.086). The tree from inter-individual DAS distance using Neighbour-Joining algorithm and the FCA analysis showed a higher internal variability in Livorno than in Ancona. STRUCTURE analysis showed the genetic uniqueness of the breeds and the presence of sub-groups in Ancona originating from a possible genetic isolation. In Chapter 4, the genetic characterization of five Italian chicken breeds (Ancona, Livornese bianca, Modenese, Romagnola and Valdarnese bianca) was described, including their remote genetic origins, the differentiation among them and their present level of biodiversity. The first aim of this study is to investigate the maternal genetic origin of five Italian local chicken breeds based on mitochondrial DNA (mtDNA) information. The second topic was to assess the genetic diversity and population structure of these chicken breeds, and to quantify the genetic relationships among them by using 27 microsatellite markers. To achieve these targets, a 506 bp fragment of the D-loop region was sequenced in 50 chickens of the five breeds. Eighteen variable sites were observed which defined 12 haplotypes. They were assigned to three clades and probably two maternal lineages. Results indicated that 90% of the haplotypes are related to clade E, which has been described previously to originate from the Indian subcontinent. For the microsatellite analysis, 137 individual blood samples from of the five Italian breeds were collected. A total of 147 alleles were detected at 27 microsatellite loci. The five Italian breeds showed a slightly higher inbreeding index (FIS = 0.08) when compared to commercial populations used as reference. Structure analysis showed a separation of the Italian breeds from these reference populations; a further sub-clustering allowed to discriminate between the five Italian breeds. Aim of the third study was to investigate the genetic diversity and relationship among sixteen Mediterranean chicken populations using sequencing mitochondrial DNA and a panel of 27 microsatellite markers (Chapter5). A 506 bp fragment of the mtDNA D-loop region was sequenced in 160 DNA samples. Twenty-five variable sites, that defined 21 haplotypes, were observed and assigned to three clades and probably three maternal lineages. The major haplotype (E1) was present in the Mediterranean populations, originates from the Indian subcontinent. Different sequences were included in haplogroup A and B that are distributed in South China and Japan. For the microsatellite analysis, 465 individual blood samples from of the sixteen Mediterranean chicken populations were collected. The results indicated that about 22% of the total variability originated from variation between the Mediterranean populations as previously reported in other European chicken breeds. Structure analysis exhibited extensive genetic admixture in many studied populations. In conclusion, suitable conservation measures should be implemented for these breeds in order to minimize inbreeding and uncontrolled crossbreeding. A special care is required for the conservation and preservation of these potentially vulnerable breeds.
Author: Simone Ceccobelli
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W72054950