三叶斑潜蝇对冷驯化的响应及不同种群耐寒性差异

【目的】研究重大入侵害虫三叶斑潜蝇（Liriomyza trifolii）对快速冷驯化和长时冷驯化的响应以及3个地理种群（湖北省武汉市、海南省海口市和安徽省安庆市）的耐寒性,为明确该虫在我国高纬度地区定殖的潜在可能性提供参考。【方法】将海南三叶斑潜蝇种群蛹和成虫在-12、-14、-16、-18、-20、-22和-24℃低温暴露30 min,选择存活率为15%—30%的温度为识别温度。设置5℃为快速冷驯化的驯化温度,12℃为长时冷驯化的驯化温度,将三叶斑潜蝇蛹和成虫置于5℃下1—6 h或置于12℃下1—6 d,再置于识别温度下30 min检测存活率,未驯化的蛹和成虫也置于识别温度下30 min作为对照,比较其冷驯化后低温存活率的差异。另外,设置5个靶标温度,分别为0、-5、-10、-15和-20℃,将3个地理种群的三叶斑潜蝇蛹在靶标温度下冷暴露2 h,比较其存活率差异。最后,利用过冷却点测定仪对3个地理种群蛹的过冷却点（supercooling point,SCP）进行测定。【结果】三叶斑潜蝇蛹和成虫暴露于-20℃下30 min后,其存活率分别为15.0%、19.6%、21.0% (介于15%—30%),因此将-20℃确定为三叶斑潜蝇的冷驯化识别温度。短时间的5℃低温暴露提高了三叶斑潜蝇蛹和成虫的耐寒性,成虫对快速冷驯化的响应更加积极。1 h和2 h的冷驯化效果最好,随着暴露时间的延长,其驯化效果会逐渐减弱直至消失。在6 d内,不同时长的12℃低温暴露均会提高三叶斑潜蝇蛹和成虫的耐寒性且经历不同时长冷驯化后其耐寒性差异较小。在5、0、-5℃的低温暴露下,海南种群与安徽、湖北种群蛹的存活率差异不显著,在-10、-15、-20℃的低温暴露下,海南种群蛹的存活率显著低于安徽和湖北种群。安徽(-22.19℃)和湖北(-22.19℃) 种群蛹的过冷却点显著低于海南种群(-21.06℃)。【结论】三叶斑潜蝇的耐寒性可以通过快速冷驯化或长时冷驯化获得增强,这可能是三叶斑潜蝇逐步向我国高纬度地区扩散的原因之一。湖北和安徽种群表现出的耐寒性较海南种群强。研究结果有助于预测三叶斑潜蝇在我国的越冬分布区域,指导其监测预警及防控。

Response of Liriomyza trifolii to Cold Acclimation and Differences of Cold Tolerance Among Different Populations

【Objective】The response of the major invasive pest Liriomyza trifolii to cold acclimation and the cold tolerance of three geographical populations (Wuhan City, Hubei Province; Haikou City, Hainan Province; Anqing City, Anhui Province) were studied to provide references for the potential colonization of L. trifolii in high latitudes of China.【Method】The pupae and adults of L. trifolii population in Hainan were exposed to low temperatures of -12, -14, -16, -18, -20, -22 and -24℃ for 30 min, and the temperature with a survival rate of 15%-30% was selected as the recognition temperature. The L. trifolii pupae and adults were put at 5℃ for 1-6 h or 12℃ for 1-6 d, and then put at the recognition temperature for 30 min to detect the survival rate. The undomesticated pupae and adults were also placed at the recognition temperature for 30 min as a control, and the difference in low-temperature survival rate after cold acclimation was compared. Besides, five target temperatures were set at 0, -5, -10, -15, and -20℃, respectively, and the pupae of three geographical populations were exposed to the target temperatures for 2 h, the difference of survival rate was studied. Finally, the supercooling point (SCP) of pupae of three geographical populations was measured by supercooling point tester.【Result】When theL. trifolii pupae and adults were exposed to -20℃ for 30 min, the survival rates were 15.0%, 19.6%, and 21.0%, respectively. Therefore, -20℃ was determined as the cold acclimation recognition temperature of L. trifolii. The cold tolerance ofL. trifolii pupae and adults was improved after rapid cold acclimation at 5℃, and the adults responded more positively to rapid cold acclimation. The effect of cold acclimation for 1 h and 2 h was the best, and the effect of rapid cold acclimation decreased gradually until disappeared with the extension of exposure time. Within 6 days, the cold tolerance ofL. trifolii pupae and adults was improved by low-temperature exposure at 12℃ for different periods, and there was little difference in cold tolerance after cold acclimation for different periods. Besides, under the low-temperature exposure of 5, 0 and -5℃, there was no significant difference in the survival rate of pupae between the Hainan population and Anhui, Hubei populations, but under the low-temperature exposure of -10, -15 and -20℃, the pupa survival rate of Hainan population was significantly lower than that of Anhui and Hubei populations. The SCP of pupae in the Anhui and Hubei populations was significantly lower than that in the Hainan population.【Conclusion】The cold tolerance of L. trifolii can be enhanced by cold acclimation, which may be one of the reasons why L. trifolii gradually spread to high latitudes in China. The cold tolerance of the Hubei and Anhui populations is stronger than that of the Hainan population. The results are helpful to predict the overwintering distribution area of L. trifolii in China and guide its monitoring, early warning, and prevention and control.