The pacific white shrimp (Litopenaeus vannamei) is one of the most cultivated aquaculture species with high economic value. It also dominates the main export commodity of cultivated shrimp in Indonesia. Vannamei cultivation is still constrained by disease attacks, especially the white spot syndrome virus (WSSV) infection. The selection of shrimp that are genetically resistant to WSSV is one of the effective ways to prevent infection. Immune genes that related to WSSV infection can be used as molecular marker for selection program.
This study aimed to compared the expression of immune genes (ALF, SOD, and ProPO) between WSSV-resistant and WSSV-susceptible shrimp families to identify potential genes as molecular marker. The 140-day-old selected vannamei shrimp (140-day of culture; DOC140) obtained from the National Broodstock Centre for Shrimp and Mollusk in Karangasem from 10 families were used to get the WSSV-resistant and WSSV-susceptible famili by comparing the survival rate (SR) after the LD70 WSSV challenge test. The expression level of immunity genes was analyzed in families with the highest and lowest SR after LD70 WSSV infection. Total RNA was extracted triplicate from gill tissue at 0 hours (before WSSV infection), 20 hours, 40 hours, 60 hours, 80 hours, and 100 hours after infection.
The ALF gene expression in shrimp with the highest SR (FI) was significantly higher (p<0.05) than in the lowest SR (FC) at 40 and 60 hours after WSSV infection (Figure 1). The expression level of the SOD gene in the FI family was also significantly higher (p<0.05) at the 40th hour, 60th hour, 80th hour, and 100th hour compared to the FC family. The expression level of the ProPO gene did not show significant differences between the FI family and the FC family. These results suggested that the ALF gene can be applied to select vannamei shrimp that are resistant to WSSV.