Cryoprotectants in lab-reared and overwintering pupae of large cabbage white, Pieris brassicae (Lepidoptera: Pieridae)

The large cabbage white, Pieris brassicae (L.), is a pest of Brassicaceae family which overwinters as a pupa on different host plants or other shelters. Little information is available on the physiological changes during overwintering of this pest and its cold tolerance. In the current study, the cryoprotectants were identified by LC/MS and their changes were examined by HPLC in specimens collected during the months of autumn and winter, as well as lab-reared pupae which treated one week at 27, 15, 10, 7, and 4 °C. The changes of glycogen content were investigated as the main source of cryoprotectants. Four compounds of trehalose, sorbitol, glucose, and inositol were identified and trehalose and sorbitol showed the highest increase in the winter months and these changes were accompanied by a significant decrease in the glycogen content. In lab-reared pupae treated in 7 and 4 °C, trehalose and sorbitol significantly increased. Therefore, it seems that trehalose and sorbitol, as the most important cryoprotectants, play a significant role in tolerating of low temperatures of winter and tolerating temperatures below 10 °C can induce the production of such compounds in this species.