寄主对桔小实蝇耐寒性的影响

为了研究寄主营养对桔小实蝇耐寒性的作用，测定了以15种果蔬饲养的桔小实蝇1日龄蛹的过冷却点(supercooling points，SCP)； 再选取南瓜、西红柿、柑桔、番石榴和杨桃等5种果蔬，测定了桔小实蝇3龄老熟幼虫、1日龄蛹、3日龄蛹、5日龄蛹、7日龄蛹和雌雄成虫的过冷却点，并观察了1日龄蛹的低温存活力。结果表明：（1）15种果蔬饲养所得的桔小实蝇1日龄蛹SCP均值在-11.03℃～-13.17℃，不同寄主发育的桔小实蝇SCP值存在显著性差异，其中以取食蒲桃的最高，为-11.03℃，取食苦瓜的最低，为-13.17℃。（2）5种果蔬饲养所得的桔小实蝇各虫态的SCP均值存在极显著差异(F_(4，863)＝35.6，P<0.01)； 同一寄主上的桔小实蝇不同虫态之间SCP均值也达到极显著性差异(F_(6，863)＝392.9，P<0.01)； 且寄主和发育龄期之间存在着极显著的交互作用(F_(24，863)＝9.4，P<0.01)。（3）桔小实蝇各发育阶段，SCP值表现一定变化： 老熟幼虫发育至1日龄蛹，SCP值变化不大； 蛹发育至3、5和7天过冷却能力明显增强，降至-20℃左右，但他们之间没有明显区别； 羽化后3～5天的成虫SCP值又升高至-10℃左右。老熟幼虫、1日龄蛹和2～3日龄成虫与3日龄、5日龄和7日龄蛹的SCP值之间有显著性差异。（4）将5种果蔬饲养所得的桔小实蝇1日龄蛹置于6℃和-3℃下进行较长时间(1～8天)和较短时间(1～8 h)的低温处理，发现番石榴、杨桃和南瓜发育的蛹经低温处理后的校正羽化率较西红柿和柑桔发育的蛹高； 同样在0℃、3℃、6℃和9℃处理(2天)的实验中，得出相似的结果。因此，本实验结果表明桔小实蝇幼虫由于生活寄主的不同使得其下一代蛹的耐寒性产生了差异，引起其差异的原因值得进一步研究。

Effect of different hostfruits on the cold hardiness of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

The influence of different host fruits on the cold hardiness of oriental frit fly Bactrocera dorsalis (Hendel) was evaluated in the laboratory. One day old pupae bred with 15 different melons and fruits were chosen to test for their supercooling points (SCP). Furthermore, the SCPs of 3rd instar larvae, one day old pupae, 3 days old pupae, 5 days old pupae, 7 days old pupae and 2-3 days old adults (male and female) bred with five host plants (pumpkin, tomato, citrus, guava and star fruit) were measured, and the survival of one day old pupae bred with these five plants at low temperatures was observed. The results showed that the mean SCPs of one day old pupae of B. dorsalis bred with 15 different host fruits ranged from -11.03℃ to -13.17℃. Moreover, these values were significantly different at 0.05 level, and these fed on rose apple had the highest SCP （-11.03℃）, while those fed on balsam pear had the lowest SCP （-13.17℃）. The mean SCPs of B. dorsalis at the same developmental stages bred with the five host fruits further tested were significantly different from each other (F_(4，863)＝35.6，P<0.01). The mean SCPs at different developmental stages of B. dorsalis bred with the same host were also markedly different from each other (F_(6，863)＝392.9，P<0.01), and there were notable interaction between host fruits and the fruit fly developmental stages (F_(24，863)＝9.4，P<0.01). There were some changes among the mean SCPs of different developmental stages of B. dorsalis. From the 3rd instar larvae to one day old pupae, the SCP values were low and there were no significant difference between them. But for the pupae of 3 days old, 5 days old and 7 days old, their SCP values decreased notably, with the lowest point -20℃; however, there were no significant difference among them. For the 2-3 days old adults (female and male), the mean SCPs increased again to -10℃. The SCP values for the 3rd instar larvae, one day old pupae and adults were significantly higher than that of pupae at other three developmental stages. In order to determine the survival response to various cold stress in different host fruits of B. dorsalis, acute low temperature (-3℃) (1-8 h) and chronic low temperature (6℃) (1-8 days) regimes were designed, the corrected survival rate of the one day old pupae fed on guava, star fruit and pumpkin were higher significantly than that of the pupae fed on tomato and citrus. By exposing them to the selected low temperatures (0℃, 3℃, 6℃ and 9℃) for 2 days, the same results were obtained. Therefore, it could be concluded that different host fruits could influence the cold hardiness of next generation of B. dorsalis, and the reason underlying this needs to be further explored.