Advances and perspectives in selecting resistance traits against the parasitic mite Varroa destructor in honey bees

Abstract

Background In spite of the implementation of control strategies in honey bee (Apis mellifera) keeping, the invasive parasitic mite Varroa destructor remains one of the main causes of colony losses in numerous countries. Therefore, this parasite represents a serious threat to beekeeping and agro-ecosystems that benefit from the pollination services provided by honey bees. To maintain their stocks, beekeepers have to treat their colonies with acaricides every year. Selecting lineages that are resistant to infestations is deemed to be a more sustainable approach. Review Over the last three decades, numerous selection programs have been initiated to improve the host–parasite relationship and to support honey bee survival in the presence of the parasite without the need for acaricide treatments. Although resistance traits have been included in the selection strategy of honey bees, it has not been possible to globally solve the V. destructor problem. In this study, we review the literature on the reasons that have potentially limited the success of such selection programs. We compile the available information to assess the relevance of selected traits and the potential environmental effects that distort trait expression and colony survival. Limitations to the implementation of these traits in the field are also discussed. Conclusions Improving our knowledge of the mechanisms underlying resistance to V. destructor to increase trait relevance, optimizing selection programs to reduce environmental effects, and communicating selection outcomes are all crucial to efforts aiming at establishing a balanced relationship between the invasive parasite and its new host.

Exploring Two Honey Bee Traits for Improving Resistance Against Varroa destructor: Development and Genetic Evaluation

“…Furthermore, these associations demonstrate that the assessment of V. destructor infestation in spring is not practical for later identifying colonies with lower mite development [ 27 ]. This may explain the low heritability for the infestation growth rate (0.13 to 0.15), which has also been identified by other studies [ 8 ]. Thus, the obtained heritability values for infestation levels in summer may result from yet-unidentified particularities of the dataset.…”

“…Currently implemented solutions, such as chemical treatments, are known to lack sustainability [ 3 , 4 , 5 , 6 , 7 ], leading to an urgent need to improve current strategies. The selection of resistant honey bees, which limit the reproduction or survival of V. destructor within the colony, is a strategy to decrease infestation levels and ultimately improve colony survival [ 8 , 9 ].…”

“…However, the correlation of the results of this test with V. destructor infestation levels is still under discussion [ 9 , 10 , 11 ]. On the other hand, most currently applied resistance traits are both time consuming and costly to assess [ 8 ]: for instance, the evaluation of suppressed mite reproduction requires the dissection of several hundred brood cells under a stereomicroscope [ 12 ], which can only be processed by a limited number of highly qualified beekeepers.…”

Reproduction of ectoparasitic mites in a coevolved system: Varroa spp.—Eastern honey bees, Apis cerana

“…for managed and wild populations of A. mellifera and A. cerana . In addition to improving our understanding of host–parasite relationships, such knowledge would benefit programs aimed at selecting A. mellifera lineages resistant to V. destructor (e.g., Büchler et al., 2010; Guichard et al., 2020; Rinderer et al., 2010) by, for example, providing threshold values for infestations and reproduction levels permitting a host–parasite equilibrium.…”

Pathways for Novel Epidemiology: Plant–Pollinator–Pathogen Networks and Global Change

“…Decreases in managed A. mellifera genetic diversity, caused by selective breeding [92], may weaken A. mellifera immune responses [93] increasing population pathogen levels. Selective pollinator breeding could increase pathogen resistance or tolerance [94], the latter potentially exacerbating pathogen spillover. Managed A. mellifera are kept at higher colony densities than occur naturally, which together with their supergeneralism positions them as a central hub or a 'superspreader' reservoir host in plant-pollinator networks (Figure 1F-H) [95].…”