Diversity and Host-Specificity of Chalkbrood, a Bee Disease
Pollinating Insects-- Biology, Management and Systematics Research
2012 Annual Report
1a.Objectives (from AD-416):
To study the natural occurrence of chalkbrood pathogens and the associated host-pathogen interactions, and to utilize this knowledge to improve disease control in social and solitary bees.
1b.Approach (from AD-416):
The University of Copenhagen (UC) will host ARS personnel at their facility in 2012, 2013 and/or 2014 (for approximately one month). These visits will facilitate the collection of Ascosphaera species in their native range, and in bees that occur in Denmark. Comparative DNA analyses will be used further improve a phylogeny of the Ascosphaera that was recently developed by some members of this team. An understanding of the host-range distribution and the evolution of pathogenicity is beginning to emerge from the initial phylogeny of these bee pathogens, however, further validated is needed using specimens collected from a greater number of bee species. In addition, the University offers an opportunity to collect large numbers of some wild bee species, providing a means to conduct bioassays to experimentally evaluate the host-range of some pathogens.
The pathogenic fungus Ascosphaera apis is ubiquitous in honey bee populations. We used the draft genome assembly of this pathogen to identify polymorphic intergenic loci. Primers were developed for five of these loci, and the species-specificities were verified using DNA from a nine closely related species. The sequence variation was compared among 12 A. apis isolates at each of these loci, two additional loci, the internal transcribed spacer of the ribosomal RNA, and at a variable part of the elongation factor sequence. The degree of variation was then compared among the different loci, and three loci were found to have the greatest detection power for distinguishing A. apis haplotypes. The described loci will help us to describe population genetic structures, to elucidate host-pathogen interactions, and to test evolutionary hypotheses for honey bees and chalkbrood. This research was published this year. In addition, a new species of Ascosphaera was isolated from alfalfa leafcutting bee nesting material and named A. subglobosa. The species description was published this year.