Selection for resistance and susceptibility to hairless-black syndrome in the honeybee

A two-way selection experiment for resistance and susceptibility to hairless-black syndrome, a probable viral disease in the honeybee, was carried out for four generations. From the parental generation of 15 colonies (reared from three basic stock colonies) tested for disease resistance, one-fifth were selected to start a resistant line and one-fifth to start a susceptible one. Thereafter these two groups were kept genetically separate and, from each tested generation, an average of about 22% of the best colonies were used as parents of the next generation. Bacteria-free inoculum, which was fed to challenge these bees, was prepared by macerating and centrifuging specific numbers of bees showing symptoms of hairless-black syndrome and collected from a number of colonies in our apiaries. Resistant and susceptible lines did not differ significantly in the first selected generation. In the second, third, and fourth generations, the two lines diverged increasingly, and in each generation, they differed statistically at the 1% level of probability.