Honey bee survival mechanisms against the parasite Varroa destructor: A systematic review of phenotypic and genomic research efforts

Authors: MONDET, FANNY - Institut National De La Recherche Agronomique (INRA); BEAUREPAIRE, ALEXIS - University Of Bern; MCFEE, ALISON - North Carolina State University; LOCKE, BARBARA - Swedish University Of Agricultural Sciences; ALAUX, CEDRIC - Institut National De La Recherche Agronomique (INRA); BLANCHARD, SOLENE - Institut National De La Recherche Agronomique (INRA); Danka, Robert; LE CONTE, YVES - Institut National De La Recherche Agronomique (INRA)

Submitted to: International Journal of Parasitology
Publication Type: Review Article
Publication Acceptance Date: 3/23/2020
Publication Date: 5/5/2020
Citation: Mondet, F., Beaurepaire, A., Mcfee, A., Locke, B., Alaux, C., Blanchard, S., Danka, R.G., Le Conte, Y. 2020. Honey bee survival mechanisms against the parasite Varroa destructor: A systematic review of phenotypic and genomic research efforts. International Journal of Parasitology. 50:433-447. https://doi.org/10-1016/ijpara.2020.03.005
DOI: https://doi.org/10.1016/j.ijpara.2020.03.005

Interpretive Summary: The parasitic mite Varroa destructor is the biggest health threat to honey bees worldwide. Infestations of varroa typically kill bee colonies unless beekeepers control the mites with chemical treatments. However, some honey bee populations around the world survive despite mite infestations. These populations survive because either natural or artificial selection has produced traitrs rendering the bees resistant or tolerant to Varroa mites. We surveyed scientific all 153 studies about bees that survive varroa mites to determine which traits are most important. A variety of traits have been verified, and several of these often occur together to help bees survive the parasite. The most commonly reported traits related to varroa resistance are suppressed mite reproduction, varroa sensitive hygiene, grooming and cell recapping. We also reviewed studies of molecular studies (genomics, transcritomics or proteomics) related to varroa resiatnce. Although many molecular features have been described as being linked to mite resistance, there is a striking amount of variation in results about the features across studies. These results highlight the need to test consistent methods in the fields of ‘omics in order to develop common working strategies to tackle biological questions.

Technical Abstract: We conducted a meta-analysis of all 153 studies published in 1984-2019 that document phenotypic features (i.e., traits) of honey bee populations either selectively bred or naturally selected for tolerance and resistance to Varroa mite parasitism, while placing a special focus on ‘omics approaches. The diversity of potential resistance and tolerance mechanisms of honey bees that survive with varroa mites is tremendous and spans a range of honey bee behaviour, individual immunity, population dynamics, and relationships with associated pathogens. The most commonly reported traits are suppressed mite reproduction, varroa sensitive hygiene, grooming and cell recapping. It is very likely that these mechanisms do not operate alone. Rather, they may function in combination and the importance of a given adaptation may vary or respond differently across environments. Future research should aim at understanding the potential link between the different traits and the reason why so little overlap stands between the studies looking at molecular pathways underlying varroa resistance and tolerance. Such effort will also help the development of practical tools to assist selection programs looking for varroa resistance and tolerance, either by offering molecular markers or by finding proxies of complex traits that could help phenotyping of colonies in the field. Phenotyping efforts and molecular maker development are two approaches that complement each other, and efficient development MAS also relies on the development of effective and reliable phenotyping tools. The analysis of the studies also highlights the need to unify efforts in the research community, while presenting the most promising traits for future efforts in selective breeding for varroa-surviving bees.