Genetic polymorphism of the 17th exon at porcine RYR1 locus: a new variant in a local Portuguese pig breed demonstrated by SSCP analysis

Until 1991, malignant hyperthermia represented a major and important economic loss in modern pork production. It is a recessive autosomal disorder with variable expression that was not known to occur in the local pig breeds from Portugal, Alentejano and Bísaro, prior to outcrossing with commercial breeds. In swine, this disorder is due to a mutation in exon 17 of the ryanodine receptor 1 (RYR1) gene, detectable through the analysis of a restriction fragment length polymorphism. We used this technique to distinguish between resistant (NN), carrier (Nn) and susceptible (nn) genotypes, with the aim of excluding carriers from the breeding programme. We further developed a rapid screening technique on the basis of SSCP (single-strand conformation polymorphism). Fifteen heterozygous (Nn) individuals were found in our sample of 48 individuals from Bísaro breed using both techniques. The absence of homozygous susceptible pigs suggests that the introduction of this allele into Bísaro breed has been recent. A genetically controlled breeding programme on the basis of our findings should help to secure the future of Bísaro pigs of which few individuals are known to exist. To date, only one mutation was found in the 5' end of exon 17 of the porcine RYR1 gene. Here we present the frequencies of this mutation and describe a new mutation detected in the Alentejano breed. PCR-SSCP analysis followed by automatic sequencing allowed the detection of this rare transition (C → T) at nucleotide 1851 of exon 17.     

Molecular evidence for fat-tailed sheep domestication

The sheep is one of the most successful and widely spread domestic animals. Archaeological evidence traces the first domestic sheep back to the Near East region around 9,000 years ago. It is also known that soon after, the domesticated sheep started to flow out of the centre of origin and spread all over the ancient world following the expansion of agriculture. Throughout time, herders, nature elements and eventually some hybridization with different wild relatives produced a multitude of breeds. However, until the advent of the molecular genetics field, very little was known about the origins of most of those breeds. Two decades after the first genetic studies, we have gathered considerable information on the origins, phylogenetic relationships and patterns of genetic diversity of the sheep across the world. Indeed, the genetic studies confirmed the Near East region as the main centre of origin and also revealed other contributions from other regions. Specifically about the fat-tailed sheep, molecular genetics was also able to link their maternal origin to a specific group. So far, modern sheep have originated from five different maternal origins. Nonetheless, the technological advances of the DNA sequencing techniques are bringing more data that is showing the complexity of the domestication process.     

Development and evaluation of a selective medium for Brucella suis

A new selective medium, named LNIV-M, has been developed for isolation of Brucella suis. In this work, we evaluated the growth of B. suis reference and field strains from domestic pigs in different basal media and the susceptibility to different antibiotics contained in the currently used Farrell's and modified Thayer-Martin media. We also determined the efficacy of LNIV-M and its diagnostic performance for isolating B. suis from wild boar tissue samples. A total of 1649 samples from 918 hunter-harvested wild boars were cultured in LNIV-M, Farrell's and modified Thayer-Martin media. One hundred and thirty-nine (8.4%) samples from 63 (6.9%) animals resulted in a positive culture. LNIV-M detected 93.6% and 62.6% of positive animals and samples, respectively, while Farrell's and modified Thayer-Martin media detected, respectively, 92.1% and 79.4% of positive animals and 58.3% and 59.7% of samples. These results confirm the adequate diagnostic performance of LNIV-M in the isolation of B. suis.     

Mitochondrial DNA variation and genetic relationships in Spanish donkey breeds (Equus asinus)

In this study, the mitochondrial DNA diversity of six Spanish donkey breeds and two African donkey populations (one from Morocco and the other from Zimbabwe) was analysed. A total of 79 animals were sequenced for 313 bp of the cytochrome b gene, and 91 individuals for 383 bp of the D‐loop region or control‐region. Sequence comparisons and phylogenetic analyses of both Spanish and African populations revealed low diversity. Only six and seven haplotypes respectively were found in cytochrome b and the D‐loop region. Relatively low nucleotide diversity (π) values were detected in these populations. The π values, from the D‐loop region, ranged from 0.0006 to 0.0169 for the Catalana and Andaluza breeds, respectively. The obtained results seem to confirm the existence of two divergent maternal lineages of African origin (Equus asinus africanus and E. a. somaliensis). In this paper the genetic relationships between these breeds are analysed and compared with those obtained in other European populations. Also, the data on the genetic relationships between the populations, obtained from nuclear DNA (microsatellites) and mitochondrial DNA (cytochrome b and D‐loop region) is argued and interpreted.