Genetic relationship between the Nordestino horse and national and international horse breeds

Unravelling of the genetic diversity, population structure, and phylogenetic relationships of the indigenous horse breeds of Pakistan

The current study aimed to evaluate the genetic diversity, level of admixture, and phylogenetic relationship, of the Pakistani horse breeds, along with their morphological characterization. Data for the body measurements showed that Morna horses had the highest values of body height, body length, chest girth, leg length, and head length, whereas the Baluchi horses had the lowest values for these traits. For the genetic diversity 64 animals, 15/breed except for Baluchi(14) and Topras(05), were genotyped by using the 17-plex equine genotyping kit. The AMOVA results showed that 13% of genetic diversity was explained by breed differences, whereas 27% and 60% came from among and within individuals respectively. The highest values of genetic diversity parameters including Na(7.29±0.29), Ne(5.73±0.28), Ho(0.74±0.05) and He(0.82±0.01) were observed for Morna, whereas their lowest values were found for Topras. However, the highest value of inbreeding coefficient (Fis) was found for Baluchi and the lowest for KB horses. Among the markers, CA425 was found as the most polymorphic and ASB23 as the least polymorphic and highly fixed marker. Results of structure analysis revealed that, except Topras, each local horse breed had very admixed genetic structure perhaps due to their continuous crossing with other breeds in the past. Moreover, the structure analysis also showed that Morna and Shiean breeds had mixing of each other which was also confirmed by the lowest value of their pairwise Fst values and likewise the phylogenetic analysis also showed their close genetic relationship with each other. The phylogenetic analysis also revealed that Shiean breed had close genetic relationship with Arabian horses. Collectively, our data showed that Morna is the largest and genetically most diverse horse breed of Pakistan, whereas Baluchi horses are the smallest in size and have the highest values of inbreeding coefficient. And the phylogeny analysis showed that Shiean breed had close genetic relationship with the Arabian.

Major inconsistencies of inferred population genetic structure estimated in a large set of domestic horse breeds using microsatellites

STRUCTURE remains the most applied software aimed at recovering the true, but unknown, population structure from microsatellite or other genetic markers. About 30% of structure-based studies could not be reproduced (Molecular Ecology, 21, 2012, 4925). Here we use a large set of data from 2,323 horses from 93 domestic breeds plus the Przewalski horse, typed at 15 microsatellites, to evaluate how program settings impact the estimation of the optimal number of population clusters K opt that best describe the observed data. Domestic horses are suited as a test case as there is extensive background knowledge on the history of many breeds and extensive phylogenetic analyses. Different methods based on different genetic assumptions and statistical procedures (dapc, flock, PCoA, and structure with different run scenarios) all revealed general, broad-scale breed relationships that largely reflect known breed histories but diverged how they characterized small-scale patterns. structure failed to consistently identify K opt using the most widespread approach, the ΔK method, despite very large numbers of MCMC iterations (3,000,000) and replicates (100). The interpretation of breed structure over increasing numbers of K, without assuming a K opt, was consistent with known breed histories. The over-reliance on K opt should be replaced by a qualitative description of clustering over increasing K, which is scientifically more honest and has the advantage of being much faster and less computer intensive as lower numbers of MCMC iterations and repetitions suffice for stable results. Very large data sets are highly challenging for cluster analyses, especially when populations with complex genetic histories are investigated.

D-loop haplotype diversity in Brazilian horse breeds

The first horses were brought to Brazil by the colonizers after 1534. Over the centuries, these animals evolved and adapted to local environmental conditions usually unsuitable for exotic breeds, thereby originating locally adapted Brazilian breeds. The present work represents the first description of maternal genetic diversity in these horse breeds based on D-loop sequences. A D-Loop HSV-I fragment of 252 bp, from 141 horses belonging to ten Brazilian breeds / genetic groups (locally adapted and specialized breeds) were analysed. Thirty-five different haplotypes belonging to 18 haplogroups were identified with 33 polymorphic sites. Haplotype diversity (varying from 0.20 to 0.96) and nucleotide diversity (varying from 0.0039 to 0.0239) was lower for locally adapted than for specialized breeds, with the same pattern observed for F_ST values. Haplogroups identified in Brazilian breeds are in agreement with previous findings in South American samples. The low variability observed mainly in locally adapted breeds, indicates that, to ensure conservation of these breeds, careful reproductive management is needed. Additional genetic characterization studies are required to support accurate decision-making.