Correlations among traits associated with American foulbrood resistance in honey bees (Apis mellifera) and potential for marker-assisted selection

Though the existence of resistance traits to American foulbrood disease (AFB) has been known since the 1930’s, their inter-correlation, heritability and contribution to overall colony-level resistance remains poorly understood. We compared the distribution of AFB resistance traits within a breeding population assembled from queens derived from eight different regions: New Zealand, Chile, Hawaii, California, British Columbia, Alberta, Saskatchewan and Ontario. The breeding population was tested for several disease resistance traits including: 1) hygienic behavior, 2) in vitro larval resistance to Paenibacillus larvae infection, 3) spore filtering efficiency of nurse bees, 4) in situ development of AFB after spray-inoculation of larval patches, and 5) whole-colony development of AFB following inoculation with infected comb. Among these traits several significant correlations existed, notably among those seemingly unrelated. Principal component analysis revealed that hygienic behavior and in situ AFB patch inoculations loaded diagonally on the first component, while larval resistance loaded diagonally to in situ AFB patch inoculations on the second component. This suggests that hygienic behavior and larval resistance to AFB may work synergistically but at different stages of the disease’s development. Estimates of quantitative genetic parameters for these resistance traits and the potential for protein-based marker-assisted selection will be discussed.