The buzz about bees and mites

Senast ändrad: 15 september 2020

Barbara Locke Grandér

One of the most important challenges facing global food security is the dramatic decline of pollinators. The honey bee (Apis mellifera) is responsible for the pollination services of 90% of the crops grown for human consumption, including nutritionally (and economically) high value crops, such as vegetables, fruits and nuts. Unfortunately, the dramatic and persistent high losses of honey bee colonies threatens this important service, not to mention the ecological consequences for maintaining wild plant biodiversity. The ectoparasitic mite, Varroa destructor, and the viruses it vectors, in particular Deformed Wing Virus (DWV), are unarguably the main cause of these high losses of honey bee colonies.

Since the introduction and global spread of the mite in the 1980s, wild honeybees in Europe and North America have been nearly completely eradicated. The survival of managed honey bees is dependent on mite control treatment by beekeepers. These treatments are overwhelmingly chemical based, increasingly ineffective and leave harmful residues in hive products. They also remove the selective pressure necessary to establish a stable host-parasite relationship, which hampers the evolution of resistance and obstructs fundamental research on natural selection host‒parasite coevolution in this new host‒parasite system.

Fortunately, a few small honeybee populations surviving extended periods without mite control (some >20 years) have been documented in Sweden, France and Norway and offer exclusive insight into the natural adaptive capacity of honeybees, while possibly holding key information for improving disease-resistance breeding. They are therefore of major interest to both scientists and beekeepers alike. 

In this talk I will present my work on characterising these populations and their naturally adapted resistant and tolerant traits that have enabled their long-term survival, including their ability to reduce the mite’s reproductive success, as well as independently acquired tolerance and resistance to the virus infections vectored by the mite. These discoveries set new norms for the enormous adaptive potential of honeybees, even in the face of existential threats, which has helped the field to shift the focus from treatment-based to resistance-breeding approaches in both research and industry. In particular, this work has added extra impetus to the conservation of honeybee genetic resources and variability.

My overall research objective is to deepen our fundamental understanding of host-parasite interactions in this system but also to utilize the knowledge acquired in my research program to provide a practical sustainable solution for the industry to the threat of varroa mites and the viruses they vector. Improved disease resistant breeding efforts would alleviate the stress on bees, beekeeping and pollination dependent agriculture.

Currently, my research program focuses on comprehensively describing resistant and tolerant phenotypes in naturally adapted honey bee populations and identifying genomic regions or target genes associated with these traits using Next Generation Sequencing (NGS) technologies. This will provide valuable information that can be applied towards developing marker-assisted selection: a powerful new approach for disease-resistant breeding that can facilitate major advances in breeding efforts and genetic stock improvement.