Background Genetic improvement of fibre-producing animal species has often induced transition from double coated to single coated fleece, accompanied by dramatic changes in skin follicles and hair composition, likely implying variation at multiple loci. Huacaya, the more common fleece phenotype in alpaca (Vicugna pacos), is characterized by a thick dense coat growing perpendicularly from the body, whereas the alternative rare and more prized single-coated Suri phenotype is distinguished by long silky fiber that grows parallel to the body and hangs in separate, distinctive pencil locks. A singlelocus genetic model has been proposed for the Suri-Huacaya phenotype, where Huacaya is recessive. Methods Two reciprocal experimental test-crosses (Suri x Huacaya) were carried out, involving a total of 17 unrelated males and 149 unrelated females. An additional dataset of 587 offspring of Suri x Suri crosses was analyzed. Segregation ratios, population genotype frequencies, and/or recombination fraction under different genetic models were estimated by maximum likelihood. Results The single locus model for the Suri/Huacaya phenotype is rejected. In addition, we present two unexpected observations: 1) a large proportion (about ¾) of the Suri animals is hybrid (with at least one Huacaya offspring), even in rearing conditions where the Huacaya trait would have been almost eliminated; 2) a model with two different values of the segregation ratio fit the data significantly better than a model with a single parameter.
Inheritance of Suri and Huacaya type of fleece in Alpaca
RENIERI, Carlo;VALBONESI, Alessandro;LA MANNA, Vincenzo;
2009-01-01
Abstract
Background Genetic improvement of fibre-producing animal species has often induced transition from double coated to single coated fleece, accompanied by dramatic changes in skin follicles and hair composition, likely implying variation at multiple loci. Huacaya, the more common fleece phenotype in alpaca (Vicugna pacos), is characterized by a thick dense coat growing perpendicularly from the body, whereas the alternative rare and more prized single-coated Suri phenotype is distinguished by long silky fiber that grows parallel to the body and hangs in separate, distinctive pencil locks. A singlelocus genetic model has been proposed for the Suri-Huacaya phenotype, where Huacaya is recessive. Methods Two reciprocal experimental test-crosses (Suri x Huacaya) were carried out, involving a total of 17 unrelated males and 149 unrelated females. An additional dataset of 587 offspring of Suri x Suri crosses was analyzed. Segregation ratios, population genotype frequencies, and/or recombination fraction under different genetic models were estimated by maximum likelihood. Results The single locus model for the Suri/Huacaya phenotype is rejected. In addition, we present two unexpected observations: 1) a large proportion (about ¾) of the Suri animals is hybrid (with at least one Huacaya offspring), even in rearing conditions where the Huacaya trait would have been almost eliminated; 2) a model with two different values of the segregation ratio fit the data significantly better than a model with a single parameter.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
