In poultry, selection programs through quantitative genetics are time consuming in case of lowly heritable traits. Several genes that to be used in selection are regarded as candidate genes that affecting economic traits in poultry and these candidate genes have successful approaches in identifying several DNA markers associated with production and reproductive traits. Candidate genes are one of the primary methods to determine the specific genes related to the economic traits and molecular genetics techniques can be used to identify these genes or their chromosomal regions in terms of Quantitative Trait Loci (QTL) that affect these traits. Using biotechnology techniques are the best way to achieve this fast genetic improvement. This approach has enabled opportunities to enhance genetic improvement programs in poultry by direct selection on genes or genomic regions that affect economic traits through marker-assisted selection (MAS) and gene introgression. Mapping of quantitative trait loci (QTL) was the perfect approach to identify genes related to complex traits at genome-wide level. Recently, genome wide association study (GWAS) was used to identify the casual genes affecting economic traits in poultry using sequences variations mainly single nucleotide polymorphism (SNP). Many genes for growth and egg production were identified in poultry using GWAS method. The objectives of this reviewed article are: 1) To apply a fine chromosomal mapping for localizing the QTL affecting economic traits in the F2 population using specific microsatellite markers or SNP's in chickens and possibly identify candidate genes and causative mutations associated with the economic traits, 2) Determining the molecular markers to be used for evaluating the genetic variability among poultry breeds, 3) Reporting and characterizing the candidate genes to be used in genetic improvement programs, 4) Detecting the molecular associations between candidate genes and growth, feeding and egg traits and disease resistance responses, 4) Determining the SNP genotypes and their associations with growth and feeding performances, egg traits and disease resistance responses, 5) Defining the genetic model for detecting the molecular associations between SNP genotypes of candidate gene and economic traits, 6) Performing genome wide association study (GWAS) in order to detect potential causative mutations and genomic regions affecting productive and reproductive traits in chickens, 7) Applying genomic selection program based on the estimated Genomic Breeding Values (GBV), and 8) Suggesting a genetic improvement program to improve the Egyptian chickens breeds and strains using molecular approaches. |
