Abstract:

Dioryctria abietella and D. sylvestrella are close relative species in the same genus, and both endanger cones of Pinus koraiensis concomitantly, but their biological and ecological behaviors are quite different. To investigate the interactions between the host P. koraiensis chemical defense and physiological adaptation of the two D. species, we analyzed the larvae midgut detoxication enzymes and protective enzymes activities in 1th, 3rd, 5th instars, and the defense enzymes in healthy, fed pine cones or top shoots at the corresponding period. The results showed that phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) activities in healthy cones and shoots were changed with the development stage. The two D. larvae feeding induced those defense enzymes activities significantly increased compared with healthy cones or tips. Detoxication enzymes and protective enzymes in the two D. species, which have different survival strategies, were quite different. D. abietella specifically fed on cone through larval stage, and their detoxication enzymes, S-transferase (GST), carboxylesterase (CarE), multi-function oxidase (MFO) in midgut were significantly higher than D. sylvestrella larvae that alternatively fed on cones and tips. There were no significant differences in superoxide dismutase (SOD) and chitinase (CT) activities in D. abietella and D. sylvestrella midgus, and the two protective enzymes activities were not related to whether transferred feeding. Phenoloxidase (PO) and peroxidase (POD) in D. sylvestrella midguts had higher activity compared with D. abietella, suggesting that the higher activity could facilitate them to avoid the threat of the transfer process. The results indicated that the physiological detoxification was the predominant survival strategies for D. abietella larvae to adapt to chemical defense of host plant, whereas D. sylvestrella larvae survived not only by carrying out the physiological detoxification but also altering feeding behaviors, especially expanding the feeding scope. Plant chemicals drove survival evolution of these two species.

Key words: Pinus koraiensis, chemical defense, Dioryctria abietella, Dioryctria sylvestrella, survival strategies