Control of VNN in Striped Jack: Selection of Spawners Based on the Detection of SJNNV Gene by Polymerase Chain Reaction(PCR).

Abstract

A preventive trial of viral nervous necrosis (VNN) in larval striped jack Pseudocaraux dentex was made by selecting virus-free spawners based on the detection of the causative virus (SJNNV) gene by polymerase chain reaction (PCR) method. PCR detection of SJNNV gene from fish was done by amplifying the target sequence (T4 : 426 bp) of the coat protein gene (RNA2). Four spawner groups, each consisting of 12 to 16 fish, were examined for the presence of SJNNV in their gonads just before spawning at one month intervals. Their offsprings (eggs and larvae) were subjected to rearing experiments to observe the occurrence of VNN.The SJNNV gene was detected from some spawners of these groups at the late spawnings. VNN occurred in larvae from spawner groups including SJNNV gene-positive fish, but not in larvae obtained from spawner groups which consisted of SJNNV gene-negative fish. These results suggest that the selection of striped jack spawners based on the detection of SJNNV gene from gonads by PCR just before spawning is efficacious for the prevention of vertical transmission of SJNNV in seed production.