Hygienic behaviour in honeybee: preliminary results of a comparison of two assays

The Western honeybee represents a relevant productive livestock due to both hive products and to its role as commercial pollinator of many agricultural crops. In the honeybee, hygienic behaviour (HB) is a heritable phenotype that confers to the colony resistance to foulbrood, chalkbrood, and to the parasitic mite Varroa destructor. Nurse bees manifesting HB are able to detect, uncap, and remove infested and/or parasitized pupae from the colony. The genetic and biochemical factors that drive the manifestation of this behaviour are under investigation. Therefore, the selection of such trait still relies on field assays. Heretofore, there are two main tests to measure HB: Pin Killed Brood (PKB) test and Freeze Killed Brood (FKB) test. Concerning FKB test, a comparison between the standard FKB test and a new variant (FKB*) of this method has been performed in order to optimize the methodology in terms of time, costs, feasibility and safety for the operator and to choose the best option for large scale phenotypic characterization. The tests were carried out at regular intervals on a cohort of unselected and unrelated colonies in the apiary of the University of Milano located in Lodi, Northern Italy. Despite the limited number of observation, the analysis shows a good correlation (r = 0.65) between FKB and FKB* and an encouraging repeatability (75%) of FKB* test. These preliminary results suggest the opportunity of further investigation even for a better standardization of FKB* methodology.