桃蚜体内次生共生菌沙雷氏菌对宿主抵御寄生蜂和高温胁迫的影响

为明确桃蚜Myzus persicae体内次生共生菌沙雷氏菌Serratia symbiotica对宿主抵抗不良环境的影响,利用叶碟法测定短翅蚜小蜂Aphelinus asychi对自然感染沙雷氏菌桃蚜、自然未感染沙雷氏菌桃蚜和人工感染沙雷氏菌桃蚜的寄生特性和取食特性,并测定烟蚜茧蜂Aphidius gifuensis对这3种处理桃蚜的寄生特性及这3种处理桃蚜经高温胁迫后的生长繁殖特性。结果显示,短翅蚜小蜂在人工感染沙雷氏菌桃蚜上的产卵率比在自然未感染沙雷氏菌桃蚜上的下降近1/2,羽化率下降1/3左右,致死率、取食率、僵蚜率均无显著差异;烟蚜茧蜂对这3种处理桃蚜的致死率、过寄生率、僵蚜率及其产卵率和羽化率等均无显著差异;这3种处理桃蚜的2龄若蚜经高温胁迫后,发育时间和寿命均显著延长,开始产蚜时间明显推迟,繁殖力和日繁殖率显著降低,繁殖历期无明显变化;高温胁迫后,人工感染沙雷氏菌桃蚜比自然未感染沙雷氏菌桃蚜开始产蚜时间提前3.9 d,繁殖力增加7.0头。表明人工感染沙雷氏菌可以提高桃蚜对短翅蚜小蜂和高温胁迫的防御作用,对烟蚜茧蜂的寄生无明显效果。

Effects of the secondary endosymbiont Serratia symbiotica in Myzus persicae on host defense against parasitoids and heat stress

To clarify the effects of secondary endosymbiont Serratia symbiotica in Myzus persicae on the host defense against adverse environment, the leaf disc method was used to measure parasitic and feeding traits of Aphelinus asychi and parasitic traits of Aphidius gifuensis to M. persicae naturally infected with S. symbiotica, M. persicae naturally uninfected with S. symbiotica, and M. persicae artificially infected with S. symbiotica. In addition, the growth and reproduction traits of the three S. symbiotica treated M. persicae after heat stress were also assessed. The results showed that the oviposition rate and emergence rate of A. asychi in M. persicae artificially infected with S. symbiotica were reduced by about a half and one third, respectively, when compared with M. persicae naturally uninfected with S. symbiotica, but the fatality rate, feeding rate and mummification rate were not reduced. The fatality rate, oviposition rate, superparasitic rate, mummification rate, and emergence rate of A. gifuensis had no differences among the three M. persicae treated with S. symbiotica. Under heat stress of the 2nd instar nymphs of the three M. persicae treated with S. symbiotica, the developmental duration and longevity prolonged significantly, and the start-oviposition time delayed obviously, while the fecundity and daily fecundity decreased greatly when compared with the untreated control but the oviposition days were not affected. After heat treatment, adult start-oviposition time of M. persicae artificially infected with S. symbiotica was 3.9 d earlier than M. persicae uninfected with S. symbiotica and its fecundity was 7.0 progenies more than M. persicae uninfected with S. symbiotica. The research indicated that artificial infection of S. symbiotica could improve defense of M. persicae against A. asychi and heat stress, but have no effect on A. gifuensis.