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Quantitative trait loci for resistance to Flavobacterium psychrophilum in rainbow trout: effect of the mode of infection and evidence of epistatic interactions

Fraslin, Clémence and Dechamp, Nicolas and Bernard, Maria and Krieg, Francine and Hervet, Caroline and Guyomard, René and Esquerré, Diane and Barbieri, Johanna and Kuchly, Claire and Duchaud, Eric and Boudinot, Pierre and Rochat, Tatiana and Bernardet, Jean Francois and Quillet, Edwige Quantitative trait loci for resistance to Flavobacterium psychrophilum in rainbow trout: effect of the mode of infection and evidence of epistatic interactions. (2018) Genetics Selection Evolution, 50 (1). 50-60. ISSN 0999-193X

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Official URL: https://doi.org/10.1186/s12711-018-0431-9

Abstract

Background : Bacterial cold-water disease, which is caused by Flavobacterium psychrophilum, is one of the major diseases that affect rainbow trout (Oncorhynchus mykiss) and a primary concern for trout farming. Better knowledge of the genetic basis of resistance to F. psychrophilum would help to implement this trait in selection schemes and to investigate the immune mechanisms associated with resistance. Various studies have revealed that skin and mucus may contribute to response to infection. However, previous quantitative trait loci (QTL) studies were conducted by using injection as the route of infection. Immersion challenge, which is assumed to mimic natural infection by F. psychrophilum more closely, may reveal different defence mechanisms. Results : Two isogenic lines of rainbow trout with contrasting susceptibilities to F. psychrophilum were crossed to produce doubled haploid F2 progeny. Fish were infected with F. psychrophilum either by intramuscular injection (115 individuals) or by immersion (195 individuals), and genotyped for 9654 markers using RAD-sequencing. Fifteen QTL associated with resistance traits were detected and only three QTL were common between the injection and immersion. Using a model that accounted for epistatic interactions between QTL, two main types of interactions were revealed. A "compensation-like" effect was detected between several pairs of QTL for the two modes of infection. An "enhancing-like" interaction effect was detected between four pairs of QTL. Integration of the QTL results with results of a previous transcriptomic analysis of response to F. psychrophilum infection resulted in a list of potential candidate immune genes that belong to four relevant functional categories (bacterial sensors, effectors of antibacterial immunity, inflammatory factors and interferon-stimulated genes). Conclusions : These results provide new insights into the genetic determinism of rainbow trout resistance to F. psychrophilum and confirm that some QTL with large effects are involved in this trait. For the first time, the role of epistatic interactions between resistance-associated QTL was evidenced. We found that the infection protocol used had an effect on the modulation of defence mechanisms and also identified relevant immune functional candidate genes.

Item Type:Article
ProdINRA Id:462601
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
French research institutions > Institut National de la Recherche Agronomique - INRA (FRANCE)
Other partners > Université Paris-Saclay (FRANCE)
Laboratory name:
Funders:
French Government BPI France ; Bretagne regional authority ; Languedoc-Roussillon regional authority ; Aquitaine regional authority ; Landes regional council ; Pyrenees Atlantiques regional council ; France Genomique national infrastructure as part of " I
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Deposited On:07 Mar 2019 18:01

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