High-resolution biomonitoring of plant pathogens and plant species using metabarcoding of pollen pellet contents collected from a honey bee hive

Abstract

The Canadian beekeeping industry is spread across the country, with the greatest proportion of managed honey bee colonies occurring in the Prairie Provinces. Nationally, the number of beekeepers has recently been trending upwards. Simultaneously, agronomic and environmental plant pest incidents are increasing due to a number of factors, including the introduction of exotic organisms through international trade, which is a major pathway for the introduction of potentially invasive alien species and quarantine pests. Therefore, regulatory agencies are interested in developing high-throughput tools to achieve earlier detection of unwanted species in order to expedite application of mitigating measures to limit the impacts of their introduction. This study evaluates the potential of pollen pellet contents collected by honey bees to monitor plant pests using metabarcoding, a high-throughput sequencing (HTS) approach for monitoring complex environmental samples. The study used the ITS1 intergenic region to target oomycetes and fungi, the ATP9-NAD9 spacer to specifically target Phytophthora species, and the ITS2 region to target plant species. From the HTS results, a number of plants that were detected corresponded to known hosts of certain pathogens or species closely related to potentially invasive plant species. Genera including phytopathogenic species found in the pollen samples comprised Fusarium sp., Ophiostoma sp., Peronospora sp., Phytophthora sp., and Pythium sp. Correlations, high entropy, and co-occurrences between certain plants and oomycetes or fungi were observed. The potential for using honey bee-collected pollen pellets to study phytopathogens in a given environment is demonstrated here, and this concept could represent a promising complementary tool for the surveillance of phytopathogens or unwanted plants with previously described air and insect sampling methods if the protocol was applied with additional genetic markers.