Reducing bee generation gaps by partial phenotyping: an interesting strategy in beekeeping selection?

Bee breeding is organized around annual cycles, following seasonal changes. The intervals between generations are therefore usually multiples of whole years. Most queens are reared in spring or early summer in temperate climates. A generation interval of one year limits phenotyping to traits that can be measured early, before the spring following queen birth. Some traits, however, can only be measured later, as is typically the case for annual honey production. Evaluating these traits in selection candidates therefore requires a generation interval of at least 2 years, a common interval in the maternal pathway. Using stochastic simulation, we studied the impact of halving the generation interval on the maternal pathway by limiting phenotyping to a trait measured early on selection candidates. The paternal generation interval was maintained at 2 years with full phenotyping.

Selection targets with varying weights on early and late traits were considered, as well as negative to positive genetic correlations between traits. Accelerating the selection plan generally increased genetic gain for two-trait selection targets, from 0% to +47% after 20 years of selection. Although inbreeding rates per generation were slightly lower in the accelerated selection program, inbreeding rates per year were significantly higher. This is due to the faster generation turnover (+33%), which results in inbreeding coefficients 20-30% higher (+0.04 to +0.07) after 20 years of selection. To avoid excessive inbreeding, the shortening of the generation interval should be accompanied by strategies designed to limit inbreeding while retaining most of the genetic gain, such as increasing the size of the selection nucleus.

Reference : 
Kistler, T., Brascamp, E.W., Basso, B. et al. How partial phenotyping to reduce generation intervals can help to increase annual genetic gain in selected honeybee populations. Heredity (2025). https://doi.org/10.1038/s41437-025-00768-8