Chalkbrood (Ascosphaera aggregata) resistance in the leafcutting bee (Megachile rotundata). II. Random matings of resistant lines to wild type

Abstract - Random matings between 3 lines of the leafcutting bee, Megachile rotundata (Fabr), selected for resistance to chalkbrood, Ascosphaera aggregata Skou, and equal numbers of the wild type resulted in an incidence of chalkbrood equal to or greater than that of the wild type. The data suggest that the trait is polygenic and readily disrupted by out-crossing. The near equal incidences of chalkbrood among female and male larvae of this haplodiploid species suggest there is no sex linkage or dosage effect. The pollen mass trait also appears to be genetically mediated, independent of disease resistance and derived along different genetic pathways in each population from which the original selections were made.