RESISTANCE TO KHV EVALUATION OF RAJADANU COMMON CARP STRAIN PRODUCED BY MARKER-ASSISTED SELECTION PROGRAM USING CYCA-DAB1*05 ALLELE AS THE MARKER

Since outbreak in 2002, koi herpesvirus (KHV) disease has become main problem of common carp farming in Indonesia causing mass mortality on farmed populations. Improvement of broodstock and seed quality through selective breeding program was one of effort to tackle the spreading of KHV in common carp. The breeding program could be accelerated using marker-assisted selection (MAS). Reserch Insitute for Fish Breeding has produced Rajadanu common carp strain resistant to KHV by marker-assisted selection program using Cyca-DAB1*05 allele as the marker. This study was conducted to evaluate the resistance to KHV infection of Rajadanu common carp using challenge test. The Majalaya common carp strain resistant to KHV (Mantap) provided by Great Office on Aquaculture Fisheries was used as a comparison.

Sixty-day-old KHV-free fish (10-15 g of body weight) with total 30 individuals per strain were adapted in 30-L aquaria at 20-22 °C for three days before challenge test. Challenge test was conducted using cohabitation and injection method. Both tests were repeated three times. Three KHV-infected fish were added into each aquarium for cohabitation method. In injection method, fish were injected intramuscularly with a lethal dose of KHV filtrate provided by Instalation Research and Development in Diseases Control. Fish were reared for 21 days at 20-22 °C, fed with commersial diet (28% protein) for two times a day. Water quality condition was maintained by allowing water exchange for up to 50% every two days. Fish mortality was recorded on a daily basis, and at least 10% of dead fish and 60 of survived fish representing each strain were checked for presence of KHV by using PCR method.

Rajadanu common carp had highly resistance to KHV on both cohabitation and injection test whose the survival rate at end of test were 98.89% and 82.22%, respectively. Rajadanu common carp was more resistant to KHV than Mantap common carp, the survival rate of Mantap common carp were 81.11% and 53.33% for cohabitation and injection test, respectively (Figure 1). Although resistant to KHV infection, not all of survived fish were KHV-free. The survived fish of Rajadanu common carp was less infected by KHV than Mantap common carp in both challenge-tests.