1a. Objectives (from AD-416):
Chalkbrood causes significant mortality in bees, especially the solitary bees, but also in honey bees. These bees are important both economically and ecologically as pollinators of flowering plants, the source of most of our fruits and vegetables. The objective is to use chalkbrood as a model system to determine (1) the host/pathogen evolutionary relationship between bees and pathogens, and (2) determine how environmental stressors (such as pesticide exposure and inadequate diet) affect bee immunity. An improved understanding of host/pathogen evolution will help us identify potential sources of new, emergent pathogens in bees and provide better guidance to regulators regarding needed importation restrictions. Improving our understanding of the effects of stress on bee immunity will help in the development of effective disease control strategies for bees, especially bees produced for agricultural pollination.
1b. Approach (from AD-416):
A. Pathogen Evolution Work: The current phylogeny of the Ascosphaera will be expanded using sequences from 3-5 DNA-regions. The current list of species that have already been sequenced is too small to substantiate any phylogenetic connections between the host and pathogen groups. Now, we will collect chalkbrood pathogens worldwide, but in particular from Asia, and especially from Asian bees used for agricultural pollination. B. Genetics of Immunity. We previously identified a large number of immune response genes from the alfalfa leafcutting bees. Now, we will conduct high-throughput sequencing of other bees species to see if we can identify similar immune response genes in other bee groups. Gene expression techniques will be used to quantify which of these genes are being activated or inhibited by environmental stress factors, such as sublethal pesticide exposure. C. Determine effects of environment on bee health, especially honey bee health, using an epidemiological approach. Compare and evaluate existing geospatial and temporal datasets on honey bee health with those on cropping patterns, pesticide use, and other environmental factors to identify patterns associated with bee declines. The analysis will eventually be expanded to include geospatial data on native bee diversity.
3. Progress Report:
This project has only existed for a few months, and is an extension of a previous collaboration to evaluated the phylogeny of the fungi that cause chalkbrood in bees, to developing an understanding of how new pathogens arise. Previously, we described the disease resistance in one host, the alfalfa leafcutting bee, to began describing the genetic and environmental factors involved in bee disease resistance. This summer we began experiments to determine if and how pesticides might affect the immune response of bees and their susceptibility to diseases, especially chalkbrood. A bioassay was conducted and samples were collected for gene expression analysis. In addition, experiments were planned to evaluate the effects of environmental factors on honey bee healthy.