ABSTRACT
Varroa destructor is a virulent ectoparasitic mite of western honeybee (Apis mellifera), and considered the greatest threat to apiculture around the world. Chemical method is widely used for the management of this mite. However, this method can easily induce the resistance of V. destructor to acaricides, toxicity of acaricides to honeybee and the residues in bee products. Therefore, many safe preventions and control techniques were developed to treat mite in recent years. Using pheromones of honeybee to control V. destructor would be a main tendency. A lot of studies indicated that Varroa mites are able to use honeybee pheromones to distinguish the development stages of the hosts, and show high selectivity for appropriate hosts at a special stage. In recent years, a lot of honey bee pheromones were reported to have effect on V. destructor, including pheromones from adult honeybee, pupa and brood. Some of them have repellent effect on V. destructor, while others have attractant effect on V. destructor. This article reviewed the progresses in pheromones categories, major chemical compositions, and their effects to V. destructor, which would suggest important avenues for further researches and applications in mite control.
Subject(s)
Bees , Pheromones , Varroidae , Acaricides , Animals , PupaABSTRACT
BACKGROUND: RNA interference (RNAi) is an effective tool to examine the function of individual genes. Carboxylesterases (CarE, EC 3.1.1.1) are known to play significant roles in the metabolism of xenobiotic compounds in many insect species. Previous studies in our laboratory found that CarE expression was up-regulated in Aphis gossypii (Glover) (Hemiptera: Aphididae) adults of both omethoate and malathion resistant strains, indicating the potential involvement of CarE in organophosphorus (OP) insecticide resistance. Functional analysis (RNAi) is therefore warranted to investigate the role of CarE in A. gossypii to OPs resistance. RESULT: CarE expression in omethoate resistant individuals of Aphis gossypii was dramatically suppressed following ingestion of dsRNA-CarE. The highest knockdown efficiency (33%) was observed at 72 h after feeding when dsRNA-CarE concentration was 100 ng/µL. The CarE activities from the CarE knockdown aphids were consistent with the correspondingly significant reduction in CarE expression. The CarE activity in the individuals of control aphids was concentrated in the range of 650-900 mOD/per/min, while in the individuals of dsRNA-CarE-fed aphids, the CarE activity was concentrated in the range of 500-800 mOD/per/min. In vitro inhibition experiments also demonstrated that total CarE activity in the CarE knockdown aphids decreased significantly as compared to control aphids. Bioassay results of aphids fed dsRNA-CarE indicated that suppression of CarE expression increased susceptibility to omethoate in individuals of the resistant aphid strains. CONCLUSION: The results of this study not only suggest that ingestion of dsRNA through artificial diet could be exploited for functional genomic studies in cotton aphids, but also indicate that CarE can be considered as a major target of organophosphorus insecticide (OPs) resistance in A. gossypii. Further, our results suggest that the CarE would be a propitious target for OPs resistant aphid control, and insect-resistant transgenic plants may be obtained through plant RNAi-mediated silencing of insect CarE expression.
