Abstract: 【Aim】 Uridine diphosphate-glycosyltransferases (UGTs) are important detoxification enzymes in insects, playing important roles in various biological processes. In China, Rhopalosiphum padi has two main life history types: holocyclic i. e. cyclical parthenogenesis (CP) and anholocyclic i. e. obligate parthenogenesis (OP). In R. padi lineages with CP life history, the parthenogenetic individuals can switch from asexual reproduction to sexual reproduction, while the R. padi lineages with OP life history do not undergo reproduction switch and reproduce exclusively through parthenogenesis throughout the year. This study aims to explore the roles of UGTs in the reproduction switch of R. padi with CP life history using two UGT inhibitors (5-nitrouracil and sulfinpyrazone). 【Methods】 After injecting two UGT inhibitors (5-nitrouracil and sulfinpyrazone)(5×10^-10 mol/individual) into wingless adults from the lineage of R. padi with CP life history, the changes in UGT contents in the aphids were measured, and the numbers of virginoparae, gynoparae and males produced by cyclical parthenogenetic R. padi adults, and the start time, end time and total time of producing virginoparae, gynoparae and males were observed and analyzed. 【Results】 The UGT contents in the wingless adults of R. padi injected with 5-nitrouracil and sulfinpyrazone were significantly lower than those in their corresponding controls (injected with ddH₂O and acetone, respectively), reduced by 35.06 and 33.98 ng/L, respectively. The individual numbers of virginoparae and gynoparae in the offspring significantly decreased by 21.00 and 20.00, when the wingless adults of R. padi were injected with 5-nitrouracil, while the individual numbers of virginoparae and males in the offspring significantly decreased by 16.10 and 6.70, when the wingless adults of R. padi were injected with sulfinpyrazone. Both inhibitors significantly delayed the start time of producing gynoparae by 1.30 d, compared to the control. Injection of 5-nitrouracil had no significant effect on the start time of producing males, while injection of sulfinpyrazone significantly delayed the start time of producing males by 2.10 d, compared to their corresponding controls. Injection of 5-nitrouracil and sulfinpyrazone both significantly advanced the end time of producing virginoparae by 2.10 and 3.20 d, respectively, and significantly delayed the end time of producing gynoparae, compared to their corresponding controls. Both UGT inhibitors significantly shortened the total time of producing virginoparae but had no significant effect on the total time of producing males, compared to their corresponding controls. Injection of 5-nitrouracil did not significantly affect the total time of producing gynoparae, whereas injection of sulfinpyrazone significantly prolonged the total time of producing gynoparae, compared to their corresponding controls. 【Conclusion】 UGTs may play an important role in the reproduction switch of R. padi with holocyclic life history.

Key words: Rhopalosiphum padi, uridine diphosphate-glycosyltransferases, inhibitors, 5-nitrouracil, sulfinpyrazone, reproduction switch