Honey bee stock genotypes do not affect the level of physiological responses to chalkbrood fungus, Ascosphaera apis.

Breeding honey bees (Apis mellifera) for physiological resistance to diseases is a highly desirable and environmentally safe approach to increasing colony survival. Selection of desirable traits is a critical element of any breeding program. In this study we investigate whether honey bee stocks differ in the level of physiological resistance to chalkbrood disease caused by Ascosphaera apis, one of the major fungal pathogens of the honey bee. The level of brood resistance to systemic mycoses caused by the fungus was determined by the survival of larvae in in vitro bioassays.

Our results showed that there was no statistical difference in individual resistance to chalkbrood disease among the three honey bee stocks (Russian, Carniolan, VSH) tested in this study. Furthermore, activation of classical immunity and cellular stress responses did not influence the fate of infected individuals, indicating that activation of the individual physiological responses may not be the primary mechanism of protection against this fungal disease. Rather, behavioral responses by adult bees, as reported previously, are likely the primary mechanism providing resistance at the colony level.