Development of pheromonal tools for honeybee breeding
The purpose of this project is to lay the groundwork for the development of natural, large-scale stock improvement programs necessary for the conservation of a principal crop pollinator, the honey bee. Currently, the decline of populations of honey bees (Apis mellifera), the primary providers of pollination services in agriculture, is a major threat to food security in the United States, given that a majority of our fruit, vegetable, and nut crops are largely or entirely (i.e. almonds) dependent on honey bee pollination (Gallai et al. 2009; Winfree, 2009). This decline is attributed to the multiple challenges these pollinators currently face, which include pressure from parasites and pathogens, exposure to pesticides, reduced nutrition, and even climate fluctuations (Potts et al. 2010). In addition, honey bee breeding currently requires a high level of technical expertise and expensive equipment to facilitate artificial insemination. Our goal is to find/develop accessible tools and methods to facilitate controlled natural mating.
Because many honey bee behaviors are mediated by pheromones, we have begun to explore the effects of a major queen pheromone (9-ODA) on the physiology and behavior of males. This pheromone has previously shown to regulate worker behavior, development/physiology, thus potentially similar impacts on drones could provide ways on regulating drone reproductive behavior. A second objective seeks to identify whether a male-produced pheromone exists and its role in mediating male mating aggregations. Currently, we have completed our first objective, having found and characterized an effect of 9-ODA on both drone physiology and reproductive behavior. Progress on our second and third objectives is ongoing. We have performed the necessary dissections and extractions of the drone mandibular glands and have identified several compounds from these samples. We tested many of the identified compounds for attraction using behavioral assays this past summer. Analysis of this dataset is ongoing and once finished will result in the completion of objective two. We are making significant strides with our third objective. Currently we are on track to have presented outcomes from this proposal at two professional/stakeholder meetings and submit the outcomes of objective one for publication by February 2016.
Objective 1: Characterize the effect of the queen pheromone, 9-ODA, on the rate of drone sexual maturation.
- Characterize Vg/Juvenile hormone levels in 9-ODA exposed/unexposed male drones. (Completed)
- Characterize the effects of 9-ODA exposure on the reproductive behavior of drones under natural colony conditions. (Completed)
Objective 2: Identify and characterize a putative drone-produced pheromone involved in the formation of drone aggregations.
- Dissect putative pheromone glands from male drones and extract the contents. (Completed)
- Analyze gland contents using GC-MS. Identify compounds produced in the glands. (Broad analysis: Completed / Targeted analysis: Ongoing)
- Ascertain the biological activity of identified gland compounds using behavioral assays. (Completed Summer 2015)
Objective 3: Disseminate the practical outcomes of these objectives to research and stakeholder communities
- Present ongoing findings at professional and stakeholder meetings. (Two presentations completed by January 2016)
- Publish findings in professional research journals. (In preparation and submission expected February 2016; June 2016)
This year we turned our focus to objective two and three, having previously successfully finished work on objective one (see year one progress report). Objective one outcomes are currently being prepared in manuscript form for publication in early 2016.
To address the goals of objective two, we completed the dissection and extraction of mandibular glands from sexually mature drones this past summer. These extracts were pooled and sent to the Metabolomics core facility on the Pennsylvania State University campus for broad GC-MS characterization. The analysis yielded a list of six compounds that we tested in the field (individually and as a blend) for biological attraction to drones, at sites adjacent to two research apiaries on The Pennsylvania State University campus. These experiments were video recorded and are currently being analyzed. We have also instigated a more sophisticated approach to identifying putative drone-produced pheromones, by dissecting and characterizing the extracts from individual drone glands and comparing the contents of those glands across many individuals. This will give us a more definitive understanding of what compounds an individual drone is producing and in what quantities. This project is expected to be complete by spring 2016.
Objective three requires us to disseminate the outcomes of objectives one and two at professional/stakeholder meetings and through publications. By February 2016, we will have submitted the findings from the completion of objective one for publication and also presented our results at two professional/stakeholders conferences. We aim to again publish our findings upon completing the work outlined in objective two in the spring of 2016.
Impacts and Contributions/Outcomes
This project has already yielded exciting and potentially useful results. We now have evidence that 9-ODA may be regulating specific features of reproductive physiology and behavior in males, providing a potential avenue for developing practical and accessible breeding methods for stock improvement programs. If the effect we produced could be scaled to a commercial breeding operation, it would allow a breeder to make the males in selected colonies more reproductively competitive than others in the same area, allowing for male stock selection to take place in a natural setting. These outcomes are currently being prepared for publication.
We have also identified for the first time the compounds produced in the mandibular glands of sexually mature drones and have also assessed their ability to elicit attractive behavior in drones. Though these analyses are still ongoing, a finding here has the potential to yield compounds that can be used to artificially increase recruitment to an area, thereby producing another tool that breeders might use to manipulate natural mating in honey bees.
Pennsylvania State University
Chemical Ecology Laboratory
University Park, PA 16802
Pennsylvania State University
Chemical Ecology Laboratory - Room 1
University Park, PA 16802