Detección de cultivos modificados genéticamente

Desde el Neolítico hemos estado modificando los diferentes cultivos para mejorar sus cualidades agrícolas, utilizando la selección y el cruzamiento como herramienta (National Research Council, 2000; Royal Society, 2000). Estas técnicas tradicionales tienen algunas limitaciones, entre las cuales destacan el largo tiempo necesario para lograr los resultados deseados (se necesitan varias generaciones para mejorar un atributo), y su uso limitado dentro de especies relacionadas genéticamente. Sin embargo, otras herramientas, como la tecnología transgénica, aceleran el proceso de mejora permitiendo que un rasgo genético se pueda insertar en una planta seleccionada a través de la introducción directa del gen responsable de ese rasgo. Además, no está restringido por la similitud genética, lo que amplía el número de fuentes potenciales del que se pueden obtener rasgos convenientes (Gelvin, 1998; Royal Society, 1998; Herbers y Sonnewald, 1999; Melchers y Stuiver, 2000)

Genetic variability and differentiation in Spanish roe deer (Capreolus capreolus): A phylogeographic reassessment within the European framework

Here we study 109 Iberian roe deer individuals corresponding to 9 Spanish populations. Individuals were sampled at locations that are expected to have acted as refugia for the species during the 20th century. Samples were analyzed for a 436 bp mtDNA fragment from the HVI region of mitochondrial DNA and 10 microsatellites. The 109 sequences gave 31 different haplotypes that enabled identification of a new haplogroup (mainly present in Northwestern Iberian populations and representing roughly a third of our samples) that is not present in other European roe deer populations. Using microsatellites, correspondence analysis and molecular coancestry information revealed high molecular differentiation among Northwestern and Central-Southern Spain roe deer populations. Both sequence and microsatellite analysis reveal that the Spanish roe deer populations are genetically heterogeneous and have high genetic structure clearly separating the Pyrenean-reintroduced populations and two main areas for the species in Spain (Northwestern and Central-Southern) coinciding with the two main areas acting as refugia for the majority of the mammal species during glaciations. The implications of the obtained information as regards the phylogeography of the species are discussed together with suggestions as to appropriate strategies for the conservation and management of populations

Testing a continuous variation in preweaning expression of muscular hypertrophy in beef cattle using field data

The hypothesis of a continuous variation in the expression of muscular hypertrophy has been tested using field data. A modification of NEUVY and VISSAC's cularity index method (Culard Index) was assayed. Expression of muscular hypertrophy showed a broad phenotypical variability. Environmental factors affecting expression of muscular hypertrophy characterised by Culard Index were calving season, age of dam, sex of calf, muscularity of dam, muscularity of sire and age of calf at weaning. In addition, Culard Index influences significantly preweaning growth traits confirming double muscled calves’ higher preweaning growth ability. Culard Index score showed moderate heritability. Expression of muscular hypertrophy could be a relatively different trait with respect to latent muscular hypertrophy that would be, in turn, determined by a partially dominant major gene. Culard Index could be an interesting tool to make use of the observable differences in expression of muscular hypertrophy.Felddaten getestet. Hierzu wurde eine Modifikation der Methode nach NEUVY und VISSAC für den Geburtsindex angewendet. Die Ausprägung der Muskelhypertrophie zeigte eine starke, phänotypische Variabilität. Die Umweltfaktoren, die die Ausprägung der Muskelhypertrophie beinflussten waren Abkalbzeit, Muskelbeschaffenheit der Elterntiere und Geschlecht der Kälber zum Entwöhnungszeitpunkt. Der Grad der Ausprägung der Muskelhypertrophie beeinflusste zudem die Wachstumsmerkmale der Kälber vor der Entwöhnung. Kälber mit Muskelhypertrophie zeigten ein stärkeres Wachstumsvermögen. Die Ausprägung der Muskelhypertrophie ist jedoch nur schwach vererbbar. Die phänotypische Ausprägung der Muskelhypertrophie könnte neben der genetischen. Bestimmung ein zusätzliches Zuchtmerkmal darstellen. Der veränderte Geburtsindex nach NEUVY und VISSAC könnte ein nützliches Hilfsmittel sein, um die Unterschiede in der Ausprägung der Muskelhypertrophie in der Praxis zur Anwendung zu bringen, z.B. in Zuchtprogrammen von Rinderrassen mit hoher Frequenz an Tieren mit Muskelhypertrophie

The coding sequence of the ASIP gene is identical in nine wild-type coloured cattle breeds

The aim of this study was to ascertain the role of the Agouti signaling peptide (ASIP) gene coding region in the Agouti locus variation within wild-type coat colour in cattle. We determined the Extension genotype in 241 individuals from six Spanish and three French brown cattle breeds representative of wild-type coat variation. Polymerase chain reaction– single-strand conformation polymorphism (PCR-SSCP) analysis was carried out in individuals of each Extension genotypes within the same breed in an attempt to identify variants in the three coding exons of the ASIP gene. No SSCP variants were found. Results were confirmed by sequencing the coding exons of the ASIP gene in 20 individuals. Our results suggest that the ASIP coding region does not play a central role in coat colour variation in cattle

Genetic variability and differentiation in Spanish roe deer (Capreolus capreolus): A phylogeographic reassessment within the European framework

Here we study 109 Iberian roe deer individuals corresponding to 9 Spanish populations. Individuals were sampled at locations that are expected to have acted as refugia for the species during the 20th century. Samples were analyzed for a 436 bp mtDNA fragment from the HVI region of mitochondrial DNA and 10 microsatellites. The 109 sequences gave 31 different haplotypes that enabled identification of a new haplogroup (mainly present in Northwestern Iberian populations and representing roughly a third of our samples) that is not present in other European roe deer populations. Using microsatellites, correspondence analysis and molecular coancestry information revealed high molecular differentiation among Northwestern and Central-Southern Spain roe deer populations. Both sequence and microsatellite analysis reveal that the Spanish roe deer populations are genetically heterogeneous and have high genetic structure clearly separating the Pyrenean-reintroduced populations and two main areas for the species in Spain (Northwestern and Central-Southern) coinciding with the two main areas acting as refugia for the majority of the mammal species during glaciations. The implications of the obtained information as regards the phylogeography of the species are discussed together with suggestions as to appropriate strategies for the conservation and management of populations

Factors affecting actual weaning weight, preweaning average daily gain and relative growth rate in Asturiana de los Valles beef cattle breed

In this paper we analyse the major environmental and genetic factors affecting actual weaning weight (WW), preweaning average daily gain (ADG) and relative growth rate (RGR) in a representative sample of field data of Asturiana de los Valles beef cattle breed. Major environmental factors affect preweaning growth performance of Asturiana de los Valles calves in the direction usually found in the literature. However RGR seems to be self-corrected for sex of calf and calving number. Heritabilities for the direct and maternal genetic effects were 0.67 and 0.29, 0.51 and 0.31 and 0.18 and 0.12 respectively for WW, ADG and RGR. The estimates of genetic parameters affecting RGR are more realistic than those estimated for the WW and ADG. Selection for RGR would lead to obtain higher growth rates and lower birth weights. RGR could be an interesting selection criterion in beef cattle improvement programs

Genetic diversity loss due to selection for scrapie resistance in the rare Spanish Xalda sheep breed

Lipid contained in embryonic cells can adversely affect survival of frozen/thawed in vitro produced (IVP) bovine embryos (Leibo et al, Theriogenology 43:265, 1995). Moreover, glycogen accumulates in excess in cells from IVP mouse embryos (Ozias and Stern, Biol Reprod, 8:467-472, 1973) and could retain water and render difficult the dehydration when freezing embryos. Mobilizing these stocks could therefore increase the ability of IVP embryos to be cryopreserved and it is known that epinephrine causes lipid and glycogen breakdown in adult tissues. Degradative products of glycogen and lipids could be used by the embryo depending on the presence of other energy substrates in the culture medium.The effects of epinephrine on the freezability of IVP embryos were evaluated. Cumulus-oocyte complexes (COCs) were matured in TCM 199, 10% fetal bovine serum (FBS) and FSHp (20 g/ml) for 24 h. Culture conditions were 39o C, 5% CO2 in air and high humidity. Matured COCs were incubated together with Percoll-separated sperm in Fert-TALP and 10 g/ml heparin for 20 h. Zygotes were vortexed for 2 min, allotted to each group and cultured in mSOF, 3g/L BSA and 10% FBS. The effect of 1M epinephrine during the initial 48 h of culture was determined in a 2 x 2 factorial design in presence (+LP) or absence (-LP) of lactate (3.3 mM) and pyruvate (0.3 mM) in mSOF. From 48 h to Day 7, culture in all groups was performed in mSOF+LP without epinephrine. Day 7 blastocysts were slowly frozen in PBS and 1.5 M ethylene glycol, thawed for 5 sec in air and 30 sec in water at 30 oC and directly rehydrated in PBS. Thawed blastocysts were cocultured for 48 hours with bovine oviductal cells. Morphological normality at thawing and blastocoelic re-expansion were the criteria for survival. Data were analyzed by ANOVA and REGWF test for means. No interactions between epinephrine and LP were detected.Both, presence of epinephrine and absence of LP during the first 48 hours of culture significantly decreased blastocyst rate. Survival rate after thawing was not altered by these treatments

Genetic analysis of days open in beef cattle F.

The aim of this work was to analyse the genetic parameters affecting days open (DO) in beef cattle to evaluate its potential as criterion of selection. The present study characterises DO as a trait with considerable genetic variability, relative to that usually found for reproduction traits, especially for heifers and second calving cows. The estimates of heritability for the trait ranged from 0.091 for cows with 10 or more calvings to 0.197 for second calving cows. The genetic correlations estimated for DO in different parities are situated between 0.9 and 1, showing that the genes affecting the trait are substantially the same across parities of the dam. A substantial permanent environment (around 9%) seems to affect DO performance. Permanent environmental factors seem to be especially important in younger cows. Genetic correlation between DO and calving interval was positive and very high (1.0), while those between DO and gestation length and calving date were negative from low to moderate (−0.089 and −0.308, respectively). DO can be used in improvement programs of beef cattle as an early indicator of reproductive performance of the cow

Quantifying diversity losses due to selection for scrapie resistance in three endangered Spanish sheep breeds using microsatellite information.

The effect of selection for scrapie resistance on genetic variability in three endangered Spanish sheep breeds (Colmenareña, Mallorquina and Rubia de El Molar) was studied using two different criteria for quantifying contributions to genetic variability: (a) molecular coancestry or genetic identity; and (b) average number of alleles per locus or allelic richness. A total of 236 (81 Colmenareña, 76 Mallorquina and 79 Rubia de El Molar) individuals were genotyped for the PrP gene and for 22 microsatellite markers. The analyses assumed a selective policy aimed at the elimination of the VRQ allele and the reduction of the frequency of the ARQ/ARQ genotype. These goals are approached by rejecting for breeding those individuals with the highest susceptibility for scrapie (risk groups R4 and R5) in a genetic scenario with no previous selection programmes considering the PrP gene polymorphism carried out. When all the individuals classified into risk groups R4 and R5 were removed from the dataset, the total molecular coancestry slightly increased in the Colmenareña breed illustrating that the carriers of undesirable PrP genotypes are not essential to maintain its overall gene diversity. When the allelic richness was considered, the removal of the R4 and R5 individuals gave high losses in the Rubia de El Molar breed. The analyses carried out considering the sex of the individuals informed that most increases in genetic identity in the Colmenareña breed resulted from the removal of the R4 and R5 males while in the Mallorquina breed resulted from the removal of the undesirable females. Losses of diversity in the Rubia de El Molar breed were basically independent of the sex of the individuals due to the balanced contributions to diversity of both sexes. As a general recommendation, not all the individuals of undesirable risk groups should be rejected for reproduction at the same time to avoid irretrievable loses of genetic diversity but according to the sex of the individuals

Relationship between genealogical and microsatellite information characterizing losses of genetic variability: Empirical evidence from the rare Xalda sheep breed

Preservation of rare genetic stocks requires continual monitoring of populations to avoid losses of genetic variability. Genetic variability can be described using genealogical and molecular parameters characterizing variation in allelic frequencies over time and providing interesting information on differentiation that occurred after the foundation of a conservation program. Here we analyze the pedigree of the rare Xalda sheep breed (1851 individuals) and the polymorphism of 14 microsatellites in 239 Xalda individuals. Individuals were assigned to a base population (BP) or 4 different cohorts (from C1 to C4) according to their pedigree information. Genetic parameters were computed at a genealogical and molecular level, namely inbreeding (F), observed (Ho) and expected (He) heterozygosity, individual coancestry coefficients (f and fm), average relatedness (AR), mean molecular kinship (Mk), average number of allele per locus (A), effective number of ancestors (fa), effective population size (Ne and Ne(m)) and founder genome equivalents (Ng and Ng(m)). In general, the computed parameters increased with pedigree depth from BP to C4, especially for the genealogical information and molecular coancestry-based parameters (fm, Mk and Ng(m)). However, Ho and He showed the highest values for C1 and the molecular heterozygote deficiency within population (FIS(m)) showed the lowest value for C1, thus indicating that loss of genetic variability occurs very soon after the implementation of conservation strategies. Although no genealogical or molecular parameters are sufficient by themselves for monitoring populations at the beginning of a conservation program, our data suggests that coancestry-based parameters may be better criteria than those of inbreeding or homozygosity because of the rapid and strong correlation established between f and f(m). However, the obtaining of molecular information in well-established conservation programs could not be justified, at least in economic term