Factores genéticos que inciden en la resistencia a enfermedades infecciosas en salmónidos y su aplicación a programas de mejoramiento

Archivos de Medicina Veterinaria (Impact Factor: 0.31). 12/2009; 42(1):1-13. DOI: 10.4067/S0301-732X2010000200002


El control de las enfermedades infecciosas es fundamental en el éxito del cultivo del salmón. El mejoramiento genético de la resistencia a enfermedades puede otorgar una opción factible y sustentable para el control de éstas. La Selección Asistida por Marcadores Moleculares (MAS) o Genes (GAS) se proyecta como una valiosa alternativa al mejoramiento convencional de la resistencia. Sin embargo, para implementar esta metodología es necesario el conocimiento previo de los factores genéticos involucrados en el carácter. En este trabajo se revisan y se discuten los aspectos más relevantes de la resistencia genética a enfermedades infecciosas en salmónidos y su aplicabilidad a programas de mejoramiento. En primer lugar, se presentan brevemente las enfermedades infecciosas más relevantes a nivel nacional. Además, se incluyen aspectos relacionados con el mejoramiento convencional para este rasgo cuantitativo, tales como criterios de selección, variación genética de la resistencia y correlaciones genéticas con otros caracteres de interés productivo. Por otra parte, se revisan tres aproximaciones moleculares utilizadas en la identificación de los factores genéticos involucrados en la resistencia: genes candidatos, con especial énfasis en el complejo mayor de histocompatibilidad (MHC) o genes MH, detección de loci de efecto cuantitativo (QTL) y estudios de expresión génica. Finalmente, se revisa y se discute en relación a la utilización de esta información molecular en la implementación de programas de mejoramiento genético que incluyan la resistencia a enfermedades infecciosas dentro de su objetivo de selección.

Download full-text


Available from: José Manuel Yáñez,
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Piscirickettsiosis (Piscirickettsia salmonis) is one of the diseases that cause large economic losses in Chilean salmon industry. Genetic improvement of disease resistance represents one strategy for controlling infectious diseases in farmed fish. However, knowledge of whether genetic variation exists for piscirickettsiosis resistance is needed in order to determine the feasibility of including this trait into the breeding goal. Using data from a challenge test performed on 2601 Atlantic salmon (Salmo salar) from 118 full-sib groups (40 half-sib groups) we found significant genetic variation for resistance to piscirickettsiosis. We used a cross sectional linear model (CSL) and a binary threshold (probit) model (THR) to ana1yze the test period survival, a linear model (LIN), Cox (COX) and Weibull (WB) frailty proportional hazards models to analyse the day at death, and a survival score (SS) model with a logit link to analyze the test-day survival. The estimated heritabilities for the different models ranged from 0.11 (SS) to 0.41 (COX). The Pearson and Spearman correlation coefficients between full-sib families estimated breeding values (EBVs) from the six statistical models were above 0.96 and 0.97, respectively. We used different data subsets, splitting the entire dataset both at random and by tank, in order to predict the accuracy of selection for each model. In both cases COX (0.8 and 0.79) and CSL (0.76 and 0.71) models showed the highest and the lowest accuracy of selection, respectively. These results indicate that resistance against P. salmonis in Atlantic salmon might be genetically improved more efficiently by means of using models which take both time to death and data censoring into account in the genetic evaluations.
    Aquaculture 08/2013; 414. DOI:10.1016/j.aquaculture.2013.08.009 · 1.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Red abalone Haliotis rufescens is one of the most valuable mollusks in the international market, but it has a low growth rate. A breeding program is being developed to increase its growth rate in Chile. We estimated the changes in direct heritability (h2), maternal/common environments heritability (m2) and genetic correlations (rG) of growth traits (shell length and width, total mass, flesh mass and foot protein as an indicator of meat quality) measured during 2 years (every 4 months) from the juvenile stage (27 months) to the adult harvesting age (51 months), in 60 full-sib red abalone families. Heritabilities for growth traits measured in juveniles and young adults (27–35 months of age), were low (0.07–0.17) and not significant. Initial low h2 were associated with significant amounts of maternal/common environmental effects (m2 = 0.4). In young adults and abalone near the harvest age (39–51 months of age) h2 were much higher (0.32–0.75). These results emphasize the importance of multiple estimations of h2 over time. Among meat quality traits, only the h2 for the flesh mass for adults at harvesting age was significant (0.15). We observed strong positive rG (>0.9) between shell sizes (easy to measure) and total and flesh masses (trait more related to market value than shell sizes but harder to measure) for adults at harvesting age. Thus, if the 5% largest 51 month old abalone were selected from the population as broodstock we expect a positively correlated response on flesh mass of 23.4%.
    Aquaculture Research 01/2014; 46(9). DOI:10.1111/are.12382 · 1.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Infectious and parasitic diseases are recognized worldwide as primary causes of economic losses in salmon production. Piscirickettsia salmonis and Caligus rogercresseyi are the main diseases affecting Chilean salmon aquaculture. In this study, we used data from experimental challenges against P. salmonis and C. rogercresseyi in full- and half-sibs from 118 families belonging to a Salmo salar breeding nucleus. Resistance against P. salmonis (SRS) was defined as the day of death of each fish and C. rogercresseyi resistance (CAL) was measured as the parasite load. We also measured body weight (BW) in full-sibs of the tested fish. We used a multi-trait animal model to estimate (co)variance components and to calculate genetic parameters. For BW we included contemporary group (sex*tank) as factor and age at harvest as a covariate. In addition, tank was included as a factor and weight at end of test as a covariate for SRS and CAL. The estimated heritabilities for BW, SRS and CAL were 0.4 (± 0.05), 0.18 (± 0.03) and 0.1 (± 0.03), respectively. The genetic correlations between BW-SRS, BW-CAL and SRS-CAL were -0.19 (± 0.12), -0.32 (± 0.14) and -0.02 (± 0.17), respectively. The levels of genetic variation and the magnitude of the genetic correlations between resistance to P. salmonis, C. rogercresseyi and body weight found in the present study demonstrate the feasibility for the improvement of these traits simultaneously by means of selective breeding.
    Aquaculture 06/2014; 433. DOI:10.1016/j.aquaculture.2014.06.026 · 1.88 Impact Factor