HIGH SURVIVAL IN THE MHC I MARKER SELECTED AFRICAN CATFISH F1 GENERATION AGAINST Aeromonas hydrophila INFECTION  

Aeromonas hydrophila infection can cause high mortality in catfish. The culture of genetically disease resistance fish can be alternative means to prevent the loss of production due to disease infection.  This study aimed to examine the resistance of African catfish F1 generation against Aeromonas hydrophila infection. F1 fishes were produced by crossing F0 broods having major histocompatibility complex (MHC) I molecular marker. Fishes having MHC I marker were identified by PCR method with ClAhMH-01 specific primer.  A total of 8 pairs of parental fishes carrying the MHC I (P) and a pair of control broodstock without MHC I marker (N) were mated to produce F1 generation. The disease resistance of the fish was examined by challenge test.  A total of 25 fish (body weight 55±7 g) of each crosses were challenged by intramuscular injection with 0.1 mL A. hydrophila (10⁶ cfu/mL).

Blood samples from three fishes from each cross were taken on day 0, 1, 3, 5 and 7 post challenged test to determine leukocytes count and antibody titers using direct agglutination method. The results showed that the survival of F1 from P broods was about 2.2 times higher than that of N brood (Table 1). Percentage of resistance (R; without injure) category offspring from P broods was 64.0-77.2%, while the survivor-wounds healed  (L) category was 9.2-18.8%, while R and L category offspring from N brood were 4.0% and 33.2%, respectively..Leukocyte count and antibody titer were in line with the high resistance of P-derived offspring against A. hydrophila infection (Fig. 1). Results of PCR analyses showed that the percentage of F1 progenies having the marker from P broods was 72%, while N fish was 25% indicating the strong linkage of MHC I marker and fish survival, and that the marker was inherited to F1 progenies.

As conclusion, high resistance of catfish against A. hydrophyla infection can be produced by MHC I marker based selection. Further research is needed to evaluate the disease resistance and marker inheritance to next generations.

Table 1. Survival and number of first generation (F1) having MHC I molecular marker from the crosses of broods having (P) and without the marker (N).