Genetic diversity in the Maremmano horse and its relationship with other European horse breeds

Download Genetic diversity in the Maremmano horse and its relationship with other European horse breeds

Post on 26-Sep-2016

212 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

<ul><li><p>doi:10.1111/j.1365-2052.2010.02102.x</p><p>Genetic diversity in the Maremmano horse and its relationship withother European horse breeds</p><p>M. Felicetti*,1, M. S. Lopes1, A. Verini-Supplizi*, A. da Camara Machado, M. Silvestrelli*,</p><p>D. Mendonca and O. Distl</p><p>*Department of Pathology, Diagnostic and Veterinary Clinic, University of Perugia, Via San Costanzo 4, 06126 Perugia, Italy.Biotechnology Centre of Azores, Department of Agriculture, University of Azores, Terra-Cha, 9701-851 Angra do Herosmo, Portugal.Institute for Animal Breeding and Genetics, University of Veterinary Medicine Hannover, Bunteweg 17p, 30559 Hannover, Germany</p><p>Summary The Maremmano is an Italian warmblood horse breed from central Italy. We characterizedthe genetic diversity and the degree of admixture in Maremmano in comparison to 14 other</p><p>European horse breeds using 30 microsatellites. Between-breed diversity explained about 9</p><p>per cent of the total genetic diversity. Cluster analysis, genetic distances and genetic dif-</p><p>ferentiation coefficients showed a close relationship of Maremmano with Hanoverian and</p><p>Lusitano in accordance with breed history.</p><p>Keywords clustering analysis, Equus caballus, Maremmano.</p><p>The Maremmano is an Italian warmblood horse mostly bred</p><p>in the provinces of Grosseto and Viterbo (Central Italy). It is</p><p>believed that the origin of this horse breed goes back to local</p><p>Etruscan horse populations which were crossbred with</p><p>modern breeds in the last centuries. Pedigree analysis of the</p><p>Maremmano horses revealed four male lines contributing</p><p>11.1% to the genetic diversity of all Maremmano stallions</p><p>(Silvestrelli 1991). In 1980, Maremmano breeders estab-</p><p>lished a stud book for Maremmano.</p><p>The objective of this study was to investigate the genetic</p><p>structure and the degree of admixture of Maremmano to-</p><p>gether with the Italian nucleus of Lipizzan and Lusitano as</p><p>well as twelve further horse breeds previously characterized</p><p>by Aberle et al. (2004). This data set consisted of Hanove-</p><p>rian, Arabian, Exmoor, Icelandic, Przewalski, Sorraia and</p><p>all German coldblood horse breeds. We used the same</p><p>marker set of 30 autosomal microsatellites and the same</p><p>PCR conditions and reference samples as described else-</p><p>where (Aberle et al. 2004).</p><p>A total of 146 animals that were not closely related were</p><p>genotyped in this study: Maremmano (n = 50), the Italian</p><p>nucleus of Lipizzan (n = 49) and Lusitano (n = 47) from</p><p>Portugal. DNA was extracted from EDTA-blood using</p><p>standard methods.</p><p>Genetic variability of the breeds genotyped in this study</p><p>was determined by the mean number of alleles, observed</p><p>and expected heterozygosities, breed-specific alleles and the</p><p>molecular variance (AMOVA) using GENALEX 6 (Peakall &amp;</p><p>Smouse 2006). Excess and deficiency of heterozygotes,</p><p>which are deviations from Hardy-Weinberg equilibrium,</p><p>were estimated using GENEPOP (Raymond &amp; Rousset</p><p>1995). Molecular genetic relationships among populations</p><p>were estimated using Wrights FST and Neis standardgenetic distance (GST; Nei 1973) by bootstrapping 1000</p><p>replicates using MICROSAT (Minch 1997). Phenograms</p><p>based on Neis GST and genetic distances among all 549animals were drawn using the unweighted pair group</p><p>method with arithmetic mean algorithm (UPGMA) by</p><p>PHYLIP (Felsenstein 1989) and displayed by TREEVIEW</p><p>(Page 1996). The Bayesian clustering procedure of</p><p>STRUCTURE was employed to investigate the genetic</p><p>structure and the degree of admixture of the 15 horse breeds</p><p>(Pritchard et al. 2000). A 20 000 initial burn-in was used,</p><p>followed by 100 000 MCMC iterations as recommended by</p><p>Falush et al. (2007) with 10 independent replicates each.</p><p>All runs used an admixture model with correlated fre-</p><p>quencies and the parameter of individual admixture alpha.</p><p>The mean number of alleles was 4.7 for the Lipizzan, 6.7</p><p>for the Lusitano and 7.3 for the Maremmano. For Marem-</p><p>mano and Lipizzan breeds the total observed heterozygosity</p><p>was higher than the expected, whereas for Lusitano breed</p><p>Address for correspondence</p><p>Prof. Dr O. Distl, Institute for Animal Breeding and Genetics, University</p><p>of Veterinary Medicine Hannover, Bunteweg 17p, 30559 Hannover,</p><p>Germany.</p><p>E-mail ottmar.distl@tiho-hannover.de</p><p>1These authors have contributed equally to this work.</p><p>Accepted for publication 20 September 2010</p><p> 2010 The Authors, Journal compilation 2010 Stichting International Foundation for Animal Genetics, 41 (Suppl. 2), 5355 53</p></li><li><p>19 out of the 30 loci showed observed heterozygosity values</p><p>lower than the expected ones (Table S1).</p><p>The AMOVA indicated that for Maremmano, Lipizzan and</p><p>Lusitano 9% of the total genetic variability is attributed to</p><p>significant differences between the horse breeds, whereas</p><p>91% of the observed variation was from within the breeds.</p><p>The AMOVA performed for the five riding horse breeds</p><p>(Maremmano, Lipizzan, Lusitano, Arabian, Hanoverian),</p><p>considered separately from the others, showed 11% of the</p><p>genetic variability due to breed differences. When the Ger-</p><p>man coldblood breeds were included, the variation among</p><p>breeds increased only slightly to 12%; with all 15 breeds the</p><p>total genetic variability rose to 14.6%.</p><p>Maremmano showed the lowest genetic differentiation</p><p>with the Hanoverian (5.5%); in addition, the Lipizzan and</p><p>Lusitano, when matched with the Maremmano, showed the</p><p>lowest FST values (11.4% and 6%, respectively). Among the</p><p>three breeds genotyped here, the Maremmano showed</p><p>the least differentiation when compared to the coldblood</p><p>breeds (Table S2). Similar results were obtained when the</p><p>genetic differentiation based on Neis GST among breed pairs</p><p>was used. The only exception was for the Maremmano,</p><p>which showed lowest genetic differentiation (14.7%) with</p><p>the Lusitano.</p><p>The phylogenetic tree based on Neis GST (Fig. 1) and thedendrogram based on the proportion of shared alleles</p><p>(Fig. S1) displayed three main clusters representing riding</p><p>horses, the Exmoor, Przewalski and Sorraia group and the</p><p>German draught horses. The Icelandic horses did not cluster</p><p>with any of the other breeds.</p><p>Clustering using STRUCTURE separated for K = 3 horses</p><p>into riding horse breeds, ancient and isolated breeds, and</p><p>German draught horses. For K = 9, Maremmano clustered</p><p>together with Lusitano, but Hanoverian and Arabian were</p><p>separate clusters. When K = 14, Maremmano and Lusitano</p><p>also clustered in their own pre-defined populations (Fig. S2;</p><p>Table S3).</p><p>From the three breeds genotyped in this study, both the</p><p>Maremmano and the Lusitano showed a high level of</p><p>genetic variability and similar to that observed for the same</p><p>breeds in other studies (Lus et al. 2007; Zuccaro et al.</p><p>2008). The high level of genetic differentiation observed for</p><p>the Maremmano may partly reflect contributions from</p><p>several breeds, although a significant proportion of the</p><p>Maremmano is descending from a reduced number of male</p><p>lines. The Italian nucleus of Lipizzan horses showed low</p><p>levels of variation similar to those observed by Achmann</p><p>et al. (2004). The small number of founders resulting in a</p><p>small effective population size and the traditional pure-</p><p>breeding system within a nucleus without any crossbreed-</p><p>ing may explain the reduced variability within the Lipizzan.</p><p>In agreement with the results of Lus et al. (2007) in the</p><p>Lusitano, levels of observed heterozygosity were lower than</p><p>their expected counterpart.</p><p>Pairwise FST values among Maremmano, Lipizzan, Lu-</p><p>sitano and Hanoverian were in a similar range as those</p><p>among closely related coldblood breeds (Aberle et al. 2004;</p><p>Druml et al. 2007). Inclusion of Hanoverian and German</p><p>coldblood increased the proportion of variance among</p><p>breeds only slightly, indicating a close relationship of these</p><p>breeds with Maremmano, Lipizzan and Lusitano in contrast</p><p>to Arabian, pony and primitive horse breeds. The two</p><p>genetic differentiation measures and the two model-based</p><p>clustering approaches also revealed a genetic proximity of</p><p>Maremmano with the Hanoverian and the Lusitano. Two</p><p>male lines founded by thoroughbred stallions (Aiace and</p><p>Ingres) and a Trakehner stallion might have created the</p><p>relationship between Maremmano and Hanoverian, as</p><p>thoroughbred and Trakehner stallions have been intensely</p><p>used in the Hanoverian warmblood (Hamann &amp; Distl 2008).</p><p>Regarding the close genetic proximity between Maremmano</p><p>and Lusitano, it is believed that Iberian horses, the ancestors</p><p>of the Lusitano and the Andalusian, were in the Stato dei</p><p>Reali Presidi di Spagna (15571800), located between Stato</p><p>Pontificio and Granducato di Toscana, and therefore might</p><p>have influenced the founder lines of the Maremmano breed.</p><p>Figure 1 Dendrogram showing the genetic relationships among the 15</p><p>horse breeds inferred from microsatellite data. The tree is based on Neisstandard genetic distance (GST). Bootstrap values higher than 50 are</p><p>shown in the tree.</p><p> 2010 The Authors, Journal compilation 2010 Stichting International Foundation for Animal Genetics, 41 (Suppl. 2), 5355</p><p>Felicetti et al.54</p></li><li><p>In conclusion, the Maremmano retained a high genetic</p><p>diversity and the results reported here can be used to pre-</p><p>vent genetic erosion of the Maremmano breed.</p><p>Acknowledgements</p><p>Thanks to Dr Luca Buttazzoni for technical support and Mr</p><p>Gianluca Alunni for expert technical assistance. This work</p><p>was supported by SELMOL-MIPAF (Silvestrelli) and by FTC</p><p>and FEDER within the projects POCTI/CVT/41890/2001</p><p>and POCI2010 Ref. GG/GGP/ME611. CBA-UAc was sup-</p><p>ported by FCT and DRCT and Lopes by DRCT M3.1.1/I/</p><p>017A/2005.</p><p>Conflict of interest</p><p>The authors have declared no potential conflicts.</p><p>References</p><p>Aberle K.S., Hamann H., Drogemuller C. &amp; Distl O. (2004) Genetic</p><p>diversity in German draught horse breeds compared with a group</p><p>of primitive, riding wild horses by means of microsatellite DNA</p><p>markers. Animal Genetics 35, 2707.</p><p>Achmann R., Curik I., Dovc P., Kavar T., Bodo I., Habe F., Marti E.,</p><p>Solkner J. &amp; Brem G. (2004) Microsatellite diversity, population</p><p>subdivision and gene flow in the Lipizzan horse. Animal Genetics</p><p>35, 28592.</p><p>Druml T., Curik I., Baumung R., Aberle K., Distl O. &amp; Solkner J.</p><p>(2007) Individual-based assessment of population structure and</p><p>admixture in Austrian, Croatian and German draught horses.</p><p>Heredity 98, 11422.</p><p>Falush D., Stephens M.W. &amp; Pritchard J.K. (2007) Inference of</p><p>population structure using multilocus genotype data, dominant</p><p>markers and null alleles. Molecular Ecology Notes 7, 5748.</p><p>Felsenstein J. (1989) PHYLIP Phylogeny inference package. Cla-</p><p>distics 5, 1646.</p><p>Hamann H. &amp; Distl O. (2008) Genetic variability in Hanoverian</p><p>warmblood horses using pedigree analysis. Journal of Animal</p><p>Science 86, 150313.</p><p>Lus C., Juras R., Oom M.M. &amp; Cothran E.G. (2007) Genetic diversity</p><p>and relationships of Portuguese and other horse breeds based on</p><p>protein and microsatellite loci variation. Animal Genetics 38, 20</p><p>7.</p><p>Minch E. (1997) MICROSAT, Version 1.5b. Stanford University</p><p>Medical Center, Stanford, California.</p><p>Nei M. (1973) Analysis of gene diversity in subdivided populations.</p><p>Proceedings of the National Academy of Sciences of the United States</p><p>of America 70, 33213.</p><p>Page R.D.M. (1996) TREEVIEW: an application to display phylo-</p><p>genetic trees on personal computers. Computer Applications in the</p><p>Biosciences 12, 3578.</p><p>Peakall R. &amp; Smouse P.E. (2006) GENALEX 6: genetic analysis in</p><p>Excel. Population genetic software for teaching and research.</p><p>Molecular Ecology Notes 6, 28895.</p><p>Pritchard J.K., Stephens M. &amp; Donnelly P. (2000) Inference of</p><p>population structure using multilocus genotype data. Genetics</p><p>155, 94559.</p><p>Raymond M. &amp; Rousset F. (1995) GENEPOP (version 1.2): popu-</p><p>lation genetics software for exact tests and ecumenicism. Journal</p><p>of Heredity 86, 14555.</p><p>Silvestrelli M. (1991) The Maremmano horse. Animal Genetic</p><p>Resources Information (FAO/UNEP) 8, 7483.</p><p>Zuccaro A., Bordonaro S., Criscione A., Guastella A.M., Perrotta G.,</p><p>Blasi M., DUrso G. &amp; Marletta D. (2008) Genetic diversity andadmixture analysis of Sanfratellano and three other Italian horse</p><p>breeds assessed by microsatellite markers. Animal 2, 9918.</p><p>Supporting information</p><p>Additional supporting information may be found in the</p><p>online version of this article.</p><p>Figure S1 UPGMA dendrogram constructed from allele-</p><p>sharing distances among 549 animals from 15 different</p><p>horse breeds.</p><p>Figure S2 Graphical presentation of the population struc-</p><p>ture analyses for a sample of 549 horses from 15 different</p><p>horse breeds obtained by STRUCTURE.</p><p>Table S1 Number of alleles, observed and expected hetero-</p><p>zygosity for Maremmano, Lusitano and Italian Lipizzan</p><p>horses (146 horses) based on 30 microsatellite loci.</p><p>Table S2 Neis standard genetic distance and Wrights dis-tance among 15 horse breeds.</p><p>Table S3 Estimated memberships to inferred clusters</p><p>obtained by STRUCTURE and individual assignments of 549</p><p>horses according to their own predefined breed or to</p><p>another breed as obtained using GeneClass2.</p><p>As a service to our authors and readers, this journal</p><p>provides supporting information supplied by the authors.</p><p>Such materials are peer-reviewed and may be re-organized</p><p>for online delivery, but are not copy-edited or typeset.</p><p>Technical support issues arising from supporting informa-</p><p>tion (other than missing files) should be addressed to the</p><p>authors.</p><p> 2010 The Authors, Journal compilation 2010 Stichting International Foundation for Animal Genetics, 41 (Suppl. 2), 5355</p><p>Genetic diversity of the Maremmano 55</p></li></ul>

Recommended

View more >