Selecting honey bees for worker brood that reduces the reproduction of Varroa destructor

Authors: Villa, Joseph; Danka, Robert; HARRIS, JEFFREY - Mississippi State University

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2016
Publication Date: 3/23/2016
Citation: Villa, J.D., Danka, R.G., Harris, J.W. 2016. Selecting honey bees for worker brood that reduces the reproduction of Varroa destructor. Apidologie ISSN: 0044-8435 (Print), 1297-9678 (On-line).

Interpretive Summary: Since their arrival in the 1980s, parasitic mites have had a serious economic impact by debilitating or killing colonies of honey bees in the United States. Beekeepers have been forced to rely on repeated chemical treatments to keep mites below harmful levels, but approaches such as using resistant lines of bees are more sustainable and long term solutions to the problem. When these mites parasitize their original honey bee hosts in Asia they hardly reproduce in cells of developing workers, suggesting that honey bees in the United States could be improved to do the same. A selection program for bees that would reduce the reproduction of mites was started in 2009 and continued until 2014. Initial tests indicated some colonies had reduced mite reproduction and others had higher levels. For the first two generations of breeding using controlled matings of low and of high reproduction colonies, the differences between lines carried from one generation to the next. In later generations, these differences were not apparent and were not influenced by a genetic component in the lines of bees. Breeding for a possible factor in developing bees that affects mites may not produce a long term or useful solution to the mite problem. Other forms of resistant bees based on characteristics where adult bees actively remove mites are more reliable. Some of these bees with behavior-based resistance are currently available for propagation by commercial queen breeders.

Technical Abstract: We investigated an effect of Apis mellifera worker brood on the reproduction of Varroa destructor as a resistance trait by conducting seven generations of bidirectional selection. Initial tests showed two-fold differences in mite fecundity (progeny per foundress mites) between colonies of different origins. In the first two generations of selection, low and high lines differed significantly in mite fecundity (2.6 vs. 2.9 and 2.3 vs. 2.8), but in five subsequent generations the average values of the low fecundity lines (ranges of 2.7 to 3.3) became indistinguishable from high lines (2.9 to 3.1). Similarly, the relationship between mite fecundity in 117 offspring colonies and in their 26 queen and 22 drone parent colonies was partly significant in the first three generations but not in subsequent generations. These findings suggest that adaptation of mites to host cues, loss of resistance alleles in a small breeding population, or environmental effects present challenges to breeding for this trait.