Resistance to a Rhabdovirus (VHSV) in Rainbow Trout: Identification of a Major QTL Related to Innate Mechanisms

Chantier qualité GAHealth control is a major issue in animal breeding and a better knowledge of the genetic bases of resistance to diseases is needed in farm animals including fish. The detection of quantitative trait loci (QTL) will help uncovering the genetic architecture of important traits and understanding the mechanisms involved in resistance to pathogens. We report here the detection of QTL for resistance to Viral Haemorrhagic Septicaemia Virus (VHSV), a major threat for European aquaculture industry. Two induced mitogynogenetic doubled haploid F2 rainbow trout (Oncorhynchus mykiss) families were used. These families combined the genome of susceptible and resistant F0 breeders and contained only fully homozygous individuals. For phenotyping, fish survival after an immersion challenge with the virus was recorded, as well as in vitro virus replication on fin explants. A bidirectional selective genotyping strategy identified seven QTL associated to survival. One of those QTL was significant at the genome-wide level and largely explained both survival and viral replication in fin explants in the different families of the design (up to 65% and 49% of phenotypic variance explained respectively). These results evidence the key role of innate defence in resistance to the virus and pave the way for the identification of the gene(s) responsible for resistance. The identification of a major QTL also opens appealing perspectives for selective breeding of fish with improved resistance

Mapping QTLs affecting Cortisol Response to Confinement Stress in Rainbow Trout

A QTL design was implemented to investigate the genetic architecture of variation in the plasma cortisol response to an acute confinement stressor. About 1000 F2 progeny (5 full-sib families) were produced from a cross between F0 grand-parents previously selected for two generations for a high or a low cortisol response after a standardized confinement stress. Plasma cortisol concentrations were recorded on 15 month-old juveniles after two successive rounds of confinement stress challenge, at one month interval. Overall, eight and five QTLs (P<0.10) were identified for plasma cortisol concentration after the first and second challenge respectively. The most significant QTLs (P<0.05) were not the same in the two challenges. The results agree with previous studies reporting genetic variation for cortisol response after exposure to a stressor, but emphasize that response to stress is a highly complex trait, and that plasma cortisol may reflect a range of underlying physiological mechanisms

Initial stages of silicon–crucible interactions in crystallisation of solar grade silicon: Kinetics of coating infiltration

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Direct bonding of titanium layers on silicon

International audienceDirect metal bonding is a key technology for 3D integration that will allow semiconductor industry to go beyond predicted problems of future ICs. In this paper, for the first time, we show room temperature direct bonding of titanium layers on silicon wafers at atmospheric pressure and ambient air. Transmission electron microscopy and spreading scanning resistance microscopy are used to investigate bonding interface. Several physical mechanisms of titanium-titanium interface sealing during subsequent thermal annealing are observed and compared to copper and tungsten in terms of bonding mechanism and temperature dependenc

Maternal and genetic effects on embryonic survival from fertilization to swim up stage and reproductive success in a farmed rainbow trout line

Reproductive success and offspring survival until sexual maturity are essential traits both for fish fitness and aquaculture development. Variation in offspring's survival among family results in unbalanced parental contributions to the next generation and may explain the loss of genetic diversity observed in some farmed populations. Therefore, we studied the variance in parental contributions to a progeny cohort, as well as the biological factors impacting offspring early survival in rainbow trout. The data consisted of 945 individual survival observations from fertilization to the juvenile stage from 135 full-sib families of the INRAE experimental synthetic line. Survival was assessed at eyed-egg stage, hatching, and 3 weeks after first feeding. We used a fullfactorial mating design to partition phenotypic variance in early survival traits into maternal and additive genetic effects under threshold GBLUP models considering the inclusion of genomic information for 32,725 SNP. Average offspring survival proportions were 91.0% at the eyed-egg stage, 87.2% at hatching, and 84.4% three weeks after first feeding. Significant unbalanced dam contributions were observed at the eyed-egg and hatching stages. Low heritability was estimated for early survival traits (h 2 =0.20 ± 0.12 and 0.13 ± 0.09 for survival from egg-eyed stage and, respectively, hatching and first feeding), revealing that additive genetic variance was not significantly different from zero, while maternal effects explained a larger part (c 2 =0.37 ± 0.16 and 0.15 ± 0.07, respectively) of the phenotypic variances. There was no evidence of inbreeding depression on survival in our study. Phenotypically, offspring early survival was positively correlated with dam fecundity, while it was negatively correlated with dam post-spawning weight. Negative, but not significant association was observed between early survival and dam's average egg weight. If a study of genetic correlations confirms these phenotypic trends, promoting high fecund females should help the breeders to increase offspring early survival and to maintain genetic diversity in breeding programs

Are resistances to acute hyperthermia or hypoxia stress similar and consistent between early and late ages in rainbow trout using isogenic lines?

International audienceGlobal warming is expected to increase the frequency and intensity of heatwaves, resulting in more common combined acute hyperthermia and hypoxia conditions in fish farms. Such poor thermal and oxygenation conditions induce problems, including growth losses, increased pathogens pressure and mortality. Selective breeding is a promising solution to improve resistance to non-optimal water quality. Indeed, genetic variability to survive in acute hyperthermia or hypoxia conditions has been proved in fish. However, the characterization of these traits is not yet detailed enough to include them in a selection program. Here, we investigated the ranking stability of genotypes for acute hyperthermia or hypoxia resistances over age and between acute hyperthermia and acute hypoxia resistances. To this end, we established rankings of six isogenic lines of rainbow trout (Oncorhynchus mykiss) for their resistance to acute hyperthermia and hypoxia stress factors at 6 and 15 months. The experimental design was robust with more than a hundred fish per line and age. There were statistically significant resistance variations among lines confirming the potential of genetic selection for these traits. Hyperthermia and hypoxia resistance rankings were found stable 1 year apart for most genotypes. Therefore, it would be possible to select for resistance to hyperthermia and hypoxia at an early stage. No overall relationship was found between acute hyperthermia and hypoxia resistance traits: some lines were resistant to both stress factors while others were resistant to one but sensitive to the other. This indicates no strong antagonistic genetic effects between acute hyperthermia and hypoxia resistance traits in rainbow trout