The following was presented at the 2010 American Bee Research Conference in Orlando, FL.
19. Melathopoulos, A.P., S.F. Pernal, A. van Hagaf & L.J. Foster VARIABILITY AND CORRELATIONS AMONG FIVE TRAITS ASSOCIATED WITH AMERICAN FOULBROOD (AFB) RESISTANCE IN A CANADIAN BREEDING POPULATION – The demonstration of AFB resistance in the 1930s lead to the discovery of several resistance traits (Spivak & Gilliam, 1998 Bee World 79:124-134, 169-186). The heritability of these traits in commercial breeding populations, their correlation and their relative contribution to overall resistance, however, remains poorly understood. For this reason we compared the distribution of AFB traits within a breeding population.
We assembled colonies in a common apiary headed by queens from eight different regions (New Zealand, Chile, Hawaii, California, British Columbia, Alberta, Saskatchewan, and Ontario). These were tested for 1) Hyg Beh: hygienic behavior, 2) Larval AFB: the percentage of in vitro reared larva with AFB after being fed Paenibacillus larva spores, 3) Nurse Spore: the retention of spores by nurse bees fed spore-containing syrup, 4) Patch AFB: the percentage of first-instar larvae in comb developing AFB in situ after inoculation and 5) Comb AFB: the number of AFB cells in colonies following inoculation with AFB-infected comb.
There were five significant correlations among the traits (Figure), the strongest being between four related traits; Hyg Beh measured at 24h versus 48h, and Nurse Spore from whole colony tests in 2008 versus cage tests in 2009. More notable, however, were correlations among a number of seemingly unrelated traits. Principal component analysis revealed that among these later traits Hyg Beh and Patch AFB (14d after infection) loaded diagonally on the first component, while Larval AFB loaded diagonally to Patch AFB (7d after infection) on the second component. This suggests that Hyg Beh and Larval AFB may work synergistically but at different stages of disease’s development. Nurse Spore loaded strongly on the third component suggesting the trait is unrelated to the other traits.
Our next step will be to estimate quantitative genetic parameters for each trait by assessing them among an F1 generation produced through a partial diallele cross of selected colonies.
More presentations from this conference can be found at Proceedings of the American Bee Research Conference 2010