Physiological changes of cold hardiness and cryoprotectants in overwintering pupae of the sugar beet moth, Scrobipalpa ocellatella
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
We have already demonstrated that sugar beet moth (SBM) Scrobipalpa ocellatella (Boyd) enter diapause as pupae in response to short-day and low temperature conditions during autumn and winter. In this study, to understand how well this pest survives in sub-zero temperatures, seasonal variations in supercooling points (SCPs), cold hardiness and specific physiological and biochemical changes were studied in field-collected and lab-reared pupae. Trehalose, glucose, glycerol and sorbitol were identified as main cryoprotectants. Trehalose, glucose and glycogen content was significantly differed between diapausing and non-diapausing pupae. The glycogen and glucose content decreased in diapausing pupae, while trehalose content was increased. Moreover, diapausing pupae showed lower oxygen consumption than non-diapausing pupae. The mean SCP of field collected pupae were decreased from November to April and reached to the lowest level (-22.77 °C) in January with minimum ambient temperature of -7 °C. Survival at sub-zero temperatures for 2 h was also greatest in January with 100% survival at -10 °C, 88.8% at -15 °C and 75.5% at -20 °C, while no pupae was alive at -25°C. Increase in temperature from February was proportional with increase in SCP and decrease in cold hardiness. These findings suggest that the sugar beet moth can physiologically regulate their body composition adapting their surroundings.
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