The effects of granulovirus on activities of phenoloxidase and protective enzymes in Plutella xylostella L.

2nd-instar larvae of diamondback moth,Plutella xylostella(L.) were feed with occlusion bodies of Plutella xylostella granulovirus(PxGV) to study effects of the virus on the activities of phenoloxidase(PO) and three protective enzymes in the insect.It was shown that,PO activity in the larvae dropped down in the first three days post infection,and further down to the bottom level in the fifth day following a significantrising in the fourth day.After that,the enzymatic activity rose up in the sixth day and stabilized until seventh day when the larvae started dying.In the control,PO activity in the larvae,which were not attacked by the virus,kept dropping down up to the end.PO activity in the larvae infected by PxGV was always much higher than that in the larvae uninfected.Among the three protective enzymes,namely catalase(CAT),superoxide dismutase(SOD),and peroxidase(POD),CAT activity in the larvae infected by PxGV kept rising from the first day to seventh day,and was significantly higher than that in the larvae uninfected.SOD and POD were less affected by infection.