TalErezab,Elad Bond (1,2), Paz Kahanov (1), Olav Rueppell (3,4), Kaira Wagoner (3), Nor Chejanovsky (1), Victoria Soroker (1)
- Department of Entomology, Agricultural Research Organization, The Volcani Institute, Israel
- The Department of Environmental Economics and Management, The Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University in Jerusalem, Israel
- Department of Biology, University of North Carolina Greensboro, USA
- Department of Biological Sciences, University of Alberta, Canada
Abstract
Honey bee colonies are prone to invasion by pests and pathogens. The combination of the parasitic mite Varroa destructor (Varroa) and the multiple viruses it vectors, is a major driver of colony losses. Breeding for hygienic behavior to reduce Varroa populations is considered a sustainable way to reduce the impact of Varroa on honey bee health. However, hygienic behavior may have a cost to the health of individual bees, both in terms of viral infection risk and immune function. To determine whether selection for hygienic behavior at the colony level is associated with trade-offs in honey bee viral infection and immune function, we compared Varroa populations, viral loads, and individual immune function between honey bee colonies that were bred for high and low hygienic behavior. Specifically, we measured Varroa infestation, Deformed wing virus DWV-A, DWV-B, Acute bee paralysis virus (ABPV), and Israeli acute paralysis virus IAPV viral genome levels in bee samples from artificially inseminated queens in our bi-directional selection program for hygienic behavior in Israel. In addition, we evaluated the expression of 12 genes from the Jak-STAT, Toll, IMD and RNAi immune pathways. We found significantly lower Varroa infestation and DWV loads in highly hygienic colonies than in colonies exhibiting low hygienic behavior. In addition, workers of the hygienic colonies had significantly higher expression of the immune genes PGRP-S2 and hymenoptaecin compared to workers from low hygienic colonies. These results indicate no trade-offs in breeding for hygienic behavior. Hygienic honey bees were associated with reduced Varroa populations and reduced DWV prevalence or load at the colony level. Individual immunity of hygienic bees was increased, which could also contribute to lower virus levels, although lower Varroa levels due to social immunity presumably contributed as well. In sum, we demonstrate multiple health benefits of breeding for honey bee hygiene.