Genetic divergence and phenotypic characterization in the Mangalarga Marchador breed

Abstract

The Mangalarga Marchador (MM) breed is characterized by its elegant size, docile temperament and for being suitable for riding. Over the years, families in southern Minas Gerais began to select animals according to their own interests and personal preferences, thus forming lineages within the breed with individual traits. Scientific research on lineages in the MM breed is scarce compared to other breeds, so there are many questions about historical claims made about them. According to the book “Costelas do Abismo” by Ricardo Casiuch, based on historical information, the existence of lineages in the breed is presente. The objectives of this work were to identify if there are lineages in the MM breed using microsatellite markers and to describe the phenotypic characterization of these lineages, so it can be used as a tool when selecting individuals according to the selection objective of each breeder. The databases used came from the Brazilian Association of MangalargaMarchador Horse Breeders. The genotyping database contained 255,257 MM horses, born between 2005 and 2021. In addition, a database with pedigree information of 622,299 animals born from 1952 to 2020 and a phenotypes database evaluated at the time of definitive registration were used. containing 303,248 animals born from 1950 to 2018. To verify the existence of genetic differences according to lineage in the breed, a discriminant analysis of principal components (DAPC) implemented by the adegenet 2.0.0 package (Jombart, 2008) of the R software was performed and to carry out the phenotypic characterization, the Kruskall Wallis test in the R software was used to compare the means of morphometric measurements. The DAPC analysis demonstrated genetic differentiation of the lineages Angai and Herdade in relation to the others. The lineage Herdade showed greater differentiation in relation to the 3 comparison groups, demonstrating that the animals of this lineage are smaller and more closely grouped, in addition to presenting higher scores for gait and morphology. Thus, this study concludes that, when compared to the historically described MM lineages, the breed does not present as many distinct genetic groups, separating it into only 3 groups (Angaí, Herdade and General), and when compared to the phenotypic characteristics, only the lineage Herdade stood out.