Genetic structure and differentiation of the Japanese extremely long-tailed chicken breed (Onagadori), associated with plumage colour variation: suggestions for its management and conservation

Variabilidade genética de 12 loci de microssatélites em galinhas crioulas Canela-Preta

RESUMO Esta pesquisa foi realizada com o objetivo de se conhecer a variabilidade genética de 12 loci de microssatélites em galinhas crioulas Canela-Preta. Foram coletadas amostras de sangue de 118 galinhas crioulas Canela-Preta, provenientes de três municípios do estado do Piauí (Oeiras, Queimada Nova e Teresina). Após extração do DNA, foram utilizados marcadores para 12 loci de microssatélites: LEI0192, LEI0209, LEI0212, LEI0217, LEI0221, LEI0234, LEI0237, LEI0248, LEI0258, MCW0081, MCW0183 e MCW0213, que foram amplificados pela técnica de reação em cadeia da polimerase (PCR). Foram obtidos 408 alelos (somando os alelos dos 12 loci), com os fragmentos variando entre 50 e 460 pares de bases. O número de alelos variou de 15 (MCW0081) a 52 (LEI0212), com média de 31,5 alelos por locus. A média de heterozigosidade esperada e o conteúdo de informações polimórficas foram, respectivamente, 0,887 e 0,909. Foram observados desvios no equilíbrio de Hardy-Weinberg e valores positivos do índice de fixação com excesso de homozigotos. Os microssatélites utilizados mostraram-se polimórficos e podem ser usados para investigações genéticas em galinhas Canela-Preta. As galinhas dos plantéis avaliados apresentam grande variabilidade gênica, o que as qualifica como importante fonte de recursos genéticos e, consequentemente, faculta a utilização delas em programas de melhoramento genético animal.

Genetic differentiation among White Leghorn lines: application of individual-based clustering approaches

Genetic differentiations among White Leghorn lines were quantified based on allele frequencies of 40 microsatellite loci. In the survey among 7 lines, a considerable degree of differentiation was estimated between each pair of lines; genetic differentiation index (pairwise F(ST)) ranged from 0.0706 to 0.2590. Furthermore, 2 genetic clustering analyses of individuals, a neighbor-joining approach based on interindividual distances and the Bayesian procedure, which can assign individuals to the origins of their lines based on information on multilocus genotypes, were applied to a pairwise comparison of line differentiation. In the clustering approaches between the lowest differentiated line pair (pairwise F(ST) = 0.0706), individuals from 2 different line origins could not be separated into 2 distinct clusters, which indicates that the genetic boundary of these lines is ambiguous. On the other hand, between the highest differentiated pair (pairwise F(ST) = 0.2590), all individuals could be strictly clustered into 2 distinct groups, consistent with the origins of their lines. In the clustering based on interindividual distances, firm separations of individuals were observed in only relatively highly differentiated pairs of lines. Furthermore, in the Bayesian procedure, even in pairs with a relatively low differentiation, individuals from 2 lines formed 2 distinct clusters according to their origins. The results of the present study suggest that chicken lines possess considerable genetic differentiation despite their common breed origin. These clustering approaches at the individual level may be useful for the genetic identification and characterization of poultry stocks.