Divergent Selection for Cytogenetic Quality in Mussel Species

France is one of the major mussel producers in Europe with two commercially important species Mytilus edulis, and M. galloprovincialis. Since 2014, French mussel farms have been vulnerable to Abnormal Mussel Mortality (AMM) with mortality rates ranging from 30 to 100%, and varying spatially and temporally. One of the proposed factors influencing mortality is the haemocyte cytogenetic quality. The purpose of this study was to estimate the response to selection of cytogenetic quality trait using a divergent selection (DS) approach for the two important mussel species cultivated in France, and explore the relationship between the cytogenetic quality and survival using a cohabitation protocol with mussels sampled in a AMM site. In January 2022, wild mussels were sampled in Agnas and in Biarritz representing M. edulis and M. galloprovincialis, respectively. Their cytogenetic quality was measured using haemolymph by flow cytometry, and a DS was applied with 1.40 intensity of selection to produce contrasted groups (high/low) as well as control group in May/June 2022. The offspring cytogenetic quality was measured in June 2023. The response to selection after one generation of mass selection on the liability scale was 1.44% for M. edulis and null for M. galloprovincialis. Mortality of high, low and control groups for each species was recorded using a cohabitation experiment from March-October 2023. In October 2023, high mortality was recorded for hatchery-produced mussels (77%), with no significant difference between species, as well as within species between the high, low and control groups. Furthermore, a non-significant from zero phenotypic correlation was observed between cytogenetic quality and survival of offspring. Nevertheless, further investigations are required to validate the genetic basis of the cytogenetic quality of the mussel species cultivated in Franc

Genomic Selection for Resistance to One Pathogenic Strain of Vibrio Splendidus in Blue Mussel Mytilus Edulis

Introduction: The blue mussel is one of the major aquaculture species worldwide. In France, this species faces a significant threat from infectious disease outbreaks in both mussel farms and the natural environment over the past decade. Diseases caused by various pathogens, particularly Vibrio spp., have posed a significant challenge to the mussel industry. Genetic improvement of disease resistance can be an effective approach to overcoming this issue. Methods: In this work, we tested genomic selection in the blue mussel (Mytilus edulis) to understand the genetic basis of resistance to one pathogenic strain of Vibrio splendidus (strain 14/053 2T1) and to predict the accuracy of selection using both pedigree and genomic information. Additionally, we performed a genome-wide association study (GWAS) to identify putative QTLs underlying disease resistance. We conducted an experimental infection involving 2,280 mussels sampled from 24 half-sib families containing each two full-sib families which were injected with V. splendidus. Dead and survivor mussels were all sampled, and among them, 348 dead and 348 surviving mussels were genotyped using a recently published multi-species medium-density 60K SNP array. Results: From potentially 23.5K SNPs for M. edulis present on the array, we identified 3,406 high-quality SNPs, out of which 2,204 SNPs were successfully mapped onto the recently published reference genome. Heritability for resistance to V. splendidus was moderate ranging from 0.22 to 0.31 for a pedigree-based model and from 0.28 to 0.36 for a genomic-based model. Discussion: GWAS revealed the polygenic architecture of the resistance trait in the blue mussel. The genomic selection models studied showed overall better performance than the pedigree-based model in terms of accuracy of breeding values prediction. This work provides insights into the genetic basis of resistance to V. splendidus and exemplifies the potential of genomic selection in familybased breeding programs in M. edulis

Response to selection for cytogenetic status and their relationship with mortality in Mytilus edulis and Mytilus galloprovincialis in France

France is one of the major mussel producers in Europe with two commercially important species, Mytilus edulis and M. galloprovincialis. Since 2014, French mussel farms have been vulnerable to Abnormal Mussel Mortality (AMM) with mortality rates ranging from 30 to 100 %, and varying spatially and temporally. One of the proposed factors influencing mortality is the haemocyte cytogenetic status. The purpose of this study was to estimate the response to selection of cytogenetic status trait using a divergent selection (DS) approach for the two important mussel species cultivated in France. In January 2022, two wild mussel population were sampled in Agnas and in Biarritz representing M. edulis and M. galloprovincialis, respectively. Their cytogenetic status was measured using haemolymph by flow cytometry, and a DS was applied with 1.40 intensity of selection to produce contrasted groups (high/low) as well as control group in May/June 2022. In June 2023, the response to selection of the cytogenetic status after one generation of mass selection was 1.44 % for M. edulis and null for M. galloprovincialis. In addition, to explore the relationship between the cytogenetic status and survival, a cohabitation experiment was conducted from March–October 2023 among the high, low and control groups, and donor mussels sampled in a AMM site. At endpoint, high mortality was recorded for hatchery-produced mussels (77 %), with no significant difference between species, as well as between the high, low and control groups within species. Furthermore, a non-significant from zero phenotypic correlation was observed between the cytogenetic status and the survival. Nevertheless, further investigations are required to validate the genetic basis of the cytogenetic status of the mussel species cultivated in France

Genomic selection for resistance to one pathogenic strain of Vibrio splendidus in blue mussel Mytilus edulis

IntroductionThe blue mussel is one of the major aquaculture species worldwide. In France, this species faces a significant threat from infectious disease outbreaks in both mussel farms and the natural environment over the past decade. Diseases caused by various pathogens, particularly Vibrio spp., have posed a significant challenge to the mussel industry. Genetic improvement of disease resistance can be an effective approach to overcoming this issue.MethodsIn this work, we tested genomic selection in the blue mussel (Mytilus edulis) to understand the genetic basis of resistance to one pathogenic strain of Vibrio splendidus (strain 14/053 2T1) and to predict the accuracy of selection using both pedigree and genomic information. Additionally, we performed a genome-wide association study (GWAS) to identify putative QTLs underlying disease resistance. We conducted an experimental infection involving 2,280 mussels sampled from 24 half-sib families containing each two full-sib families which were injected with V. splendidus. Dead and survivor mussels were all sampled, and among them, 348 dead and 348 surviving mussels were genotyped using a recently published multi-species medium-density 60K SNP array.ResultsFrom potentially 23.5K SNPs for M. edulis present on the array, we identified 3,406 high-quality SNPs, out of which 2,204 SNPs were successfully mapped onto the recently published reference genome. Heritability for resistance to V. splendidus was moderate ranging from 0.22 to 0.31 for a pedigree-based model and from 0.28 to 0.36 for a genomic-based model.DiscussionGWAS revealed the polygenic architecture of the resistance trait in the blue mussel. The genomic selection models studied showed overall better performance than the pedigree-based model in terms of accuracy of breeding values prediction. This work provides insights into the genetic basis of resistance to V. splendidus and exemplifies the potential of genomic selection in family-based breeding programs in M. edulis

Genetic parameters for resistance to field mortality outbreaks and resistance to a pathogenic strain of Vibrio splendidus in Mytilus edulis, Mytilus galloprovincialis and natural hybrid

Since 2014, abnormal mussel mortality (AMM) outbreaks have occurred along the French Atlantic coasts and mortality rates differed among years and sites (30–100%). Still, the etiology of the AMM is undefined. Our study explores the resistance of two mussel species (Mytilus edulis and Mytilus galloprovincialis) and natural hybrids (NH) cultivated in France to AMM. One hundred mussel families were produced using six wild mussel populations in January/February 2017. Mussels were tested in two sites, La Floride (LF) and Maison Blanche (MB), in October 2017, and their mortality/growth was recorded until June 2018. AMM was observed at MB during spring 2018, and reached 70%, 43%, and 63%, for M. edulis, M. galloprovincialis, and NH, respectively, at endpoint. In contrast, mortality was low in LF, reaching 11%, 30%, and 22%, respectively. Heritability for mortality was low to moderate in both sites ranging from 0.12 to 0.37 with higher values in M. edulis, intermediate for NH, and the lowest for M. galloprovincialis. A significant genotype-by-environment interaction was found for mortality between sites, with low genetic correlations not significantantly different from zero (−0.05 to 0.43). In July 2018, mussel families were evaluated under experimental infection using a pathogenic strain of Vibrio splendidus isolated during AMM in 2014. The mean mortality after 72 h post-injection was 53%, 22%, and 31% for M. edulis, M. galloprovincialis, and NH, respectively. The lowest heritability estimates were obtained for NH (0.21) and the highest for M. galloprovincialis (0.41), and the genetic correlation between AMM in MB and experimental infection was not significantly different from 0, suggesting that this Vibrio strain, is not the major cause of AMM outbreak observed in MB in 2018. Finally, significant genetic variation was observed for growth traits with mostly high heritability (> 0.44) for both species. Interestingly, genetic correlation between mortality and growth was weak and non-significant from zero

Genetic parameters for resistance to field mortality outbreaks and resistance to a pathogenic strain of Vibrio splendidus in Mytilus edulis, Mytilus galloprovincialis and natural hybrid

International audienc

Corrigendum to "Genetic parameters for resistance to field mortality outbreaks and resistance to a pathogenic strain of Vibrio splendidus in Mytilus edulis, Mytilus galloprovincialis and natural hybrid" [Aquaculture, Volume 590]

International audienceThe authors regret that a few minor errors were found in the meth odology and supplementary section of our published article. While these do not impact the fundamental conclusions of our study, they could lead to potential misinterpretations by readers. Below, we provide the necessary corrections