Fleece variation in alpaca (Vicugna pacos): a two-locus model for the Suri/Huacaya phenotype

Abstract

BackgroundGenetic 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 fibre that grows parallel to the body and hangs in separate, distinctive pencil locks. A single-locus genetic model has been proposed for the Suri-Huacaya phenotype, where Huacaya is recessive.ResultsTwo reciprocal experimental test-crosses (Suri × Huacaya) were carried out, involving a total of 17 unrelated males and 149 unrelated females. An additional dataset of 587 offspring of Suri × Suri crosses was analyzed. Segregation ratios, population genotype frequencies, and/or recombination fraction under different genetic models were estimated by maximum likelihood. The single locus model for the Suri/Huacaya phenotype was rejected. In addition, we present two unexpected observations: 1) a large proportion (about 3/4) of the Suri animals are segregating (with at least one Huacaya offspring), even in breeding 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.ConclusionsThe data support a genetic model in which two linked loci must simultaneously be homozygous for recessive alleles in order to produce the Huacaya phenotype. The estimated recombination rate between these loci was 0.099 (95% C.L. = 0.029-0.204). Our genetic analysis may be useful for other species whose breeding system produces mainly half-sib families.

Analysis of genetic distance between Peruvian Alpaca (Vicugna Pacos) showing two distinct fleece phenotypes, Suri and Huacaya, by means of microsatellite markers

“…This is mainly true at the level of farming and breeder associations in North America and in Australia who often recommend considering and managing the two phenotypes as two separate breeds in order to keep the Suri line pure (Holt, 2005;Walker, 2006;Baychelier, 2002). This is not supported by present scientific knowledge, which suggests that the phenotype fleece type is a qualitative trait determined by 1 or 2 loci (Ponzoni et al, 1997;Renieri et al, 2009b;Presciuttini et al, 2010).…”

Genetic parameters estimation for preweaning traits and their relationship with reproductive, productive and morphological traits in alpaca

“…Huacaya and Suri variants are raised by this farm. They have been called breeds in the past, but they will be called variants here given that it has been shown that these varieties are explained by a very low number of genes (Presciuttini et al, 2010). Records were obtained from PacoPro v.5.2, the software used for animal husbandry management of Pacomarca experimental farm that contained 4330 females and 3788 males from 6396 and 1722 animals for Huacaya and Suri variants, respectively.…”

Determination of Schirmer tear test‐1 values in clinically normal alpacas (Vicugña pacos) in North America

“…The alpaca ( Vicugña pacos ) is an important member of the South American camelid family, which also includes the llama ( Lama glama ), guanaco ( Lama guanico ), and vicuña ( Vicugña vicugña ). Two breeds of alpaca are recognized, the Huacaya and the Suri, each having their own fiber characteristics . With the increasingly popular alpaca population, there is a growing need to establish normal ocular parameters to allow for an accurate, thorough ophthalmic examination.…”