Genetic diversity of Apis mellifera complementary sex determiner (csd) in four Australian breeding populations

Honey bee (Apis mellifera) breeding has intensified as populations experience increasing stress and pollination demand increases. Breeding programmes risk genetic diversity losses as mating is focused on a small group of individuals. Loss of diversity at the complementary sex determiner (csd) locus results in decreased viability and reduced honey production. Bees that are homozygous at csd become inviable males rather than workers. We examined csd diversity in four Australian breeding populations: a queen bee breeder from New South Wales, another from Queensland, a Western Australian breeding programme involving 11 bee breeders, and a research population at the NSW Department of Primary Industries. We found 82 unique csd alleles across the four populations, 16 of which have not been previously reported. This study provides a snapshot of csd diversity in Australia which will be useful for the national honey bee genetic improvement programme (Plan Bee).