Diapause characteristics and cold-hardiness of temperate and subtropical populations in Chilo suppressalis

Chino. 研究了二化螟[Chilo suppressalis (Walker)]北京和福州两个地理种群滞育诱导、低温存活、过冷却点和滞育幼虫抗寒生理指标的变化。结果表明，北京种群在22℃、25℃和28℃下滞育诱导的临界光周期分别为13 h 55 min、13 h 44 min和13 h 6 min，显著长于福州种群的12 h 35 min、12 h 30 min和12 h 25 min。采自于北京的田间种群滞育幼虫过冷却点达-15.13℃，显著低于北京实验种群(-8.28℃)和福州实验种群(-7.60℃)，表明自然环境的调节与诱导作用和滞育幼虫的抗寒性高度相关。在-25℃～-10℃测试范围内，随着温度下降，二化螟滞育幼虫的死亡率明显上升，但不同种群的死亡率有明显差异。在相同低温下北京实验种群的半致死时间(LT50)长于福州种群，表明随着地理纬度的上升，二化螟种群的耐寒性增强。二化螟滞育与非滞育幼虫的体重差异显著，滞育幼虫体内含水量低于非滞育幼虫，但蛋白质及糖的含量均高于非滞育幼虫，表明幼虫体内蛋白质、糖和水含量与抗寒性密切相关。

Inglés. Diapause inducement, super-cooling point, and mortality under low temperature environment and physiological index in relation to cold-hardiness in Chilo suppressalis populations from different geographical locations were studied in the laboratory. The results showed that the critical photoperiods of Beijing population at 22℃, 25℃ and 28℃ were 13 h and 55 min, 13 h and 44 min, and 13 h and 6 min, respectively, which were significantly longer than those of Fuzhou population at the same temperature. The super-cooling point of -15.13℃ for the diapause larvae collected from field in Beijing was drastically lower than both lab populations from Beijing and Fuzhou, indicating that there was a close relationship between larval cold hardiness and regulation from natural environment. During the test range from - 25℃ to -10℃, the mortality of diapause larvae increased as the temperature dropped, but there was a significant difference between two geographical populations, in which the high latitude population (Beijing) possessed a stronger cold hardiness. The weight of the diapausing larvae was significantly higher than non- diapausing ones developed under similar condition, and the water content in the diapause larvae was much lower. However, the protein and sugar contents in the diapause larvae were all higher than those in the non-diapause ones, suggesting that there were positive relationships between larval cold hardiness and the contents of protein and sugar.