EVALUATION OF THE GENETIC EFFECT OF STRAINS HYBRIDIZATION ON RESISTANCE TO Aeromonas hydrophila IN Heterobranchus bidorsalis

Abstract

Estimates of heterosis, maternal effect and general combining ability for resistance to Aeromonas hydrophila in
Heterobranchus bidorsalis were obtained from a complete diallel cross of nine (9) full siblings among three
strains; Dadinkowa, Kainji and Owena using two male (♂) and four females (♀) from each ecological zones in
Nigeria. Fishes (250 ± 16.8g) from all the genetic crosses were challenged using intraperitoneal injection and the
survival was observed over a period of three weeks. Mean survival following challenge test was 67.18± 2.9% and
ranged from 50.3 % in the Kainji (♂) X Owena (♀) to 82.6 % in the Dadinkowa (♂) X Kainji (♀). Specific
heterosis was significant (P<0.05) in the Dadinkowa (♂) X Kainji (♀) cross which suggest that intraspecific
hybridization in the two strains may increase disease resistance to A. hydrophila. Line effect was also significant (P
<0.05) in the Dadinkowa strain. There were significant maternal effect and combining ability in the Dadinkowa and
Kainji strains which implies there is prospect for improvement in diseases resistance against A. hydrophila in H.
bidorsalis through continuous selection of the Dadinkowa line and crossing of this line of fish, with lines of the
Kainji strain.