Variations des capacités reproductrices de l'escargot « Petit-gris », Helix aspersa Müller (Mollusque Gastéropode Pulmoné Stylommatophore), selon son origine géographique. II. Incubation des oeufs et éclosion des jeunes

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Genetic parameters of caviar yield, color, size and firmness using parentage assignment in an octoploid fish species, the Siberian sturgeon Acipenser baerii

International audienceAquaculture is presently the only sustainable way of enhancing sturgeon caviar production as the use of wild stocks is banned throughout the world. Hence sustainable management and efficient genetic improvement of domesticated populations are major challenges for the development of farmed caviar. We estimated genetic parameters of caviar yields and quality traits (size, color and firmness) in the polyploid Siberian sturgeon A. baerii, one of the major sturgeon species farmed for meat and caviar worldwide. This study was performed in commercial breeding conditions, where two factorial mating plans were created to produce 77 families. Larvae were pooled at hatching and reared in common environment until the age of caviar production. We phenotyped 494 females, which were successfully assigned to their parents with microsatellite markers using a newly developed software, designed to manage genotypes with varying ploidy levels, up to 8 N. The genetic parameters were estimated using heteroscedastic multi-trait BLUP animal models. Heritability of body weight, ovary weight, caviar weight, caviar (egg) size, caviar yield, caviar firmness and caviar color were moderate to high (0.13 to 0.66) depending on the trait. Moderate negative genetic correlations were estimated between growth and caviar yields (−0.28 to −0.37) while genetic correlations between caviar (egg) size and caviar yield were more negative (−0.70 to −0.76). These results provide favorable grounds to improve the efficiency of farmed caviar production by selective breeding

Genetic architecture and genomic selection of female reproduction traits in rainbow trout

International audienceBackground: Rainbow trout is a significant fish farming species under temperate climates. Female reproduction traits play an important role in the economy of breeding companies with the sale of fertilized eggs. The objectives of this study are threefold: to estimate the genetic parameters of female reproduction traits, to determine the genetic architecture of these traits by the identification of quantitative trait loci (QTL), and to assess the expected efficiency of a pedigree-based selection (BLUP) or genomic selection for these traits.Results: A pedigreed population of 1343 trout were genotyped for 57,000 SNP markers and phenotyped for seven traits at 2years of age: spawning date, female body weight before and after spawning, the spawn weight and the egg number of the spawn, the egg average weight and average diameter. Genetic parameters were estimated in multi-trait linear animal models. Heritability estimates were moderate, varying from 0.27 to 0.44. The female body weight was not genetically correlated to any of the reproduction traits. Spawn weight showed strong and favourable genetic correlation with the number of eggs in the spawn and individual egg size traits, but the egg number was uncorrelated to the egg size traits. The genome-wide association studies showed that all traits were very polygenic since less than 10% of the genetic variance was explained by the cumulative effects of the QTLs: for any trait, only 2 to 4 QTLs were detected that explained in-between 1 and 3% of the genetic variance. Genomic selection based on a reference population of only one thousand individuals related to candidates would improve the efficiency of BLUP selection from 16 to 37% depending on traits.Conclusions: Our genetic parameter estimates made unlikely the hypothesis that selection for growth could induce any indirect improvement for female reproduction traits. It is thus important to consider direct selection for spawn weight for improving egg production traits in rainbow trout breeding programs. Due to the low proportion of genetic variance explained by the few QTLs detected for each reproduction traits, marker assisted selection cannot be effective. However genomic selection would allow significant gains of accuracy compared to pedigree-based selection

Detection of QTL controlling metabolism, meat quality, and liver quality traits of the overfed interspecific hybrid mule duck

Chantier qualité GAInternational audienceThe mule duck, an interspecific hybrid obtained by crossing common duck (Anas platyrhynchos) females with Muscovy (Cairina moschata) drakes, is widely used for fatty liver production. The purpose of the present study was to detect and map single and pleiotropic QTL that segregate in the common duck species, and influence the expression of traits in their overfed mule duck offspring. To this end, we generated a common duck backcross (BC) population by crossing Kaiya and heavy Pekin experimental lines, which differ notably in regard to the BW and overfeeding ability of their mule progeny. The BC females were mated to Muscovy drakes and, on average, 4 male mule ducks hatched per BC female (1600 in total) and were measured for growth, metabolism during growth and the overfeeding period, overfeeding ability, and the quality of their breast meat and fatty liver. The phenotypic value of BC females was estimated for each trait by assigning to each female the mean value of the phenotypes of her offspring. Estimations allowed for variance, which depended on the number of male offspring per BC and the heritability of the trait considered. The genetic map used for QTL detection consisted of 91 microsatellite markers aggregated into 16 linkage groups (LG) covering a total of 778 cM. Twenty-two QTL were found to be significant at the 1% chromosome-wide threshold level using the single-trait detection option of the QTLMap software. Most of the QTL detected were related to the quality of breast meat and fatty liver: QTL for meat pH 20 min post mortem were mapped to LG4 (at the 1% genome-wide significance level), and QTL for meat lipid content and cooking losses were mapped to LG2a. The QTL related to fatty liver weight and liver protein and lipid content were for the most part detected on LG2c and LG9. Multitrait analysis highlighted the pleiotropic effects of QTL in these chromosome regions. Apart from the strong QTL for plasma triglyceride content at the end of the overfeeding period mapped to chromosome Z using single-trait analysis, all metabolic trait QTL were detected with the multitrait approach: the QTL mapped to LG14 and LG21 affected the plasma cholesterol and triglyceride contents, whereas the QTL mapped to LG2a seemed to impact glycemia and the basal plasma corticosterone content. A greater density genetic map will be needed to further fine map the QTL