Genetic differentiation of Ukrainian chicken breeds using various types of molecular genetic markers

Modern poultry breeding is aimed towards maximizing productive performance and genetic potential of chicken breeds and lines used for different purposes in order to obtain the greatest profit. Prevalence of foreign highly productive commercial chicken lines and crosses is determined by several factors, the most important of which are the high productivity of chicken lines, as well as the lack of support and ineffective implementation of programs targeted to genetic conservation of native breeds. Preferences given to highly productive chicken breeds in breeding and poultry farming also have negative effects which manifest in a reduced genetic diversity due to narrow specialization of selected breeds and lead to the reduction of national genetic resources. The study of genetically determined features of different chicken breeds is one of the priority tasks of the gene pool conservation problem. In this study, we used two types of molecular genetic markers, PCR-RFLP and Indel, to investigate the genetic differentiation of Ukrainian chicken breeds in comparative aspect based on polymorphism of different functional genes whose allelic variants are associated with productive traits. The Ukrainian chicken breeds for different primary use, i.e. Borkovskaya Barvistaya line A, Plymouth Rock White line G-2, Poltava clay line 14 and Rhode Island Red line 38, were compared. Genetic differentiation of the chicken populations was performed by analyzing frequencies of alleles in polymorphic loci of prolactin gene ( PRL ), growth hormone gene ( GH ), insulin-like growth factor I gene ( IGF-I ), gene family of transforming growth factors b ( TGF-b1, TGF-b2 and TGF-b3 ), pituitary transcription factor-1 gene ( PIT-1 ) and Mx gene ( Mx ). For generalized estimation of breed diversity, the genetic distances were calculated based on the studied polymorphic loci for both PCR-RFLP and Indel markers. The most genetically distant breeds were Borkovskaya Barvistaya and Rhode Island Red (24.9 % of the differences). In general, the largest differences can be noted between the egg-lying and dual-purpose chicken breeds. In this, the allelic differences with the lines used for both eggs and meat were most pronounced (23-25 %). Differences between the breeds of dual use, i.e. primary for meat and eggs or for eggs and meat, were not expressed enough. Maximum differences were between populations of Poltava clay and Plymouth Rock White chicken (11.2 %), while minimum differences were between Rhode Island Red and White Plymouth Rock chicken (4.2 %). In turn, the genetic distance between the two egg-meat breeds studied was intermediate compared to the above-mentioned (7.1 % difference). The pattern of phylogenetic tree corresponds to the previously described regularities and reflects differentiation of the chicken lines by their primary use. As follows from the dendrogram, the chickens of egg-meat primary use form a separate cluster. At the same time, meat-egg and egg-lying chickens form separate branches, while the egg-lying breed shows the greatest genetic differences compared to the other lines.