Detection of DNA-based markers to analyse genetic variability in pig breeds

anglais. Type I markers at different loci (albumin, arachidonate, 12-lipoxygenase,aminopeptidase N, gamma-glutamyl transpeptidase, glucose phosphate isomerase, orosomucoid and transferrin) of the porcine genome were used to study the level of genetic variability in several pig breeds and to infer phylogenetic relationships among the breeds. 53 unrelated animals belonging to different breeds (15 large White, 6 Landrace, 6 Belgian Landrace, 10 Duroc, 6 Hampshire, 6 Pietrain) were screened for the presence of RFLPs. In Southern analysis, DNA was digested with 10 restriction enzymes and hybridized with omologous probes. The RFLPs detected in the first screening were analysed a larger sample. Moreover, 9 animals belonging to the Chinese breed Meishan were included in the analysis and data were used only in phenetic analysis. The genoma region analysed in this study was about 320 kb (0.01% of the porcine genome) and about 3% of the restriction sites were polymorphic. 24 RFLPs were analysed (21 with 2 alleles, 3 with 3 alleles). Allele frequencies, heterozigosity (H) and polymorphism information content (PIC) for every RFLP were calculated. Large White showed the highest level of variability (24 RFLPs detected and average eterozigosity of 0.3756) while Hampshire and Belgian Landrace showed the lowest one (16 RFLPs detected in each breed and average heterozigosity of 0.1997 and 0.2563, respectively). Standard genetic distances according to Nei were calculated. Using the UPGMA method with bootstrap resampling the dendrogram that shows the phylogenetic relationships among the breeds was obtained. The Chinese breed Meishan branched apart from the Euro-American breeds. The latter branch was clustered into two groups. One contains Large White, Landrace and Duroc and the other one contains Pietrain, Belgian Landrace and Hampshire breeds

italien. Sono stati considerati per l'analisi di variabilita' genetica nelle razze suine 24 RFLP (21 biallelici e 3 triallelici) in 8 diversi loci: albumina, aminopeptidasi N, arachidonato 12-lipossigenasi, colina acetil transferasi, gamma-glutamil transpeptidasi, glucosio fosfato isomerasi, orosomucoide e transferrina. Gli RFLP sono stati analizzati mediante analisi Southern di campioni di DNA appartenenti a diverse razze suine (Large White, Landrace, Landrace Belga, Duroc, Hampshire e Pietrain) utilizzando diverse endonucleasi di restrizione. Per le ibridazioni sono state utilizzate sonde omologhe. Per ognuno degli RFLP analizzati sono state calcolate le frequenze alleliche, il grado di eterozigosi (H) e il livello di polimorfismo (PIC). Per ciascuna razza e' stato calcolato il grado di eterozigosi media. Alcuni dei polimorfismi presentano valori elevati di H e di PIC e potrebbero essere utilizzati per la costruzione di mappe di associazione. Le razze esaminate hanno mostrato differenze nella distribuzione dei polimorfismi individuati e nei valori di eterozigosi media. La razza Large White ha presentato il maggior grado di variabilita', mentre Hampshire e Landrace Belga hanno presentato i valori piu' bassi. Utilizzando le frequenze alleliche dei marcatori sono state calcolate le distanze genetiche e le relazioni filogenetiche tra le razze suine. E' stato ottenuto, per la prima volta con l'uso di RFLP, un dendrogramma che indica le piu' probabili relazioni filogenetiche tra le razze considerate