Phenoloxidase activity in haemolymph of Spodoptera litura (Fabricius) mediating immune responses challenge with entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillmin

The present study was carried out to investigate the effect of entomopathogenic fungus, Beauveria bassiana on immune response mediated Phenoloxidase enzyme of Spodoptera litura larvae. To measure the PO enzyme activity, haemolymph of 3rd, 4th and 5th instar larvae of S. litura were treated with different doses of 1.0×108, 2.0×107, 4.0×106 and 8.5×105 spores/ml of B. bassiana. The results indicated increase in PO activity with increase in B. bassiana infection but subsequently decreased in all instars. Significant increase in PO level was observed @ 4.0×1062.0×107 spores/ml after 24 hrs of infection in 3rd and 4th instar larvae. However, no significant effect of B. bassiana was observed on 5th instar larvae after 24 hr of treatment but there was a remarkable increase in PO level after 48 hrs. At higher concentration, after 48 hr of infection 3rd and 4th instar larvae showed significant decrease in PO activity. After72 hrs of infection all the treatments showed suppression in PO activity as compared to control. We would like to conclude that PO was an important key enzyme that triggered immune response in S. litura larvae against the invasion of B. bassiana.