Honey bee selection: achievements, problems, and prospects

The honey bee (Apis mellifera L.) is one of the most important managed insect pollinators worldwide. In recent years, negative processes have been occurring in honey bee populations all over the world, Russia included. Of particular concern are the mass mortality of bees due to decreased adaptation of bee colonies to environmental factors and the hybridization of bees due to replacement of native populations by gentle and productive commercial lines. Nowadays, honey bee selection is a promising area of world beekeeping which is aimed at improving and breeding new lines and breeds that are highly productive, resistant to diseases, and adapted to local climate and honey flow conditions. The review is devoted to the issues of honeybee selection and includes an analysis of the problems and achievements of classical selection, and an assessment of prospects for the introduction of molecular selection into beekeeping. In most selection and breeding programs, economic and behavioral traits, primarily honey productivity, colony strength, gentle temper, and low swarming tendency have been of predominant importance. Other selective traits, such as viability, disease resistance, and local adaptation are considered less significant since their insufficient manifestation can be compensated by caring for the bees, for example, pharmaceuticals, artificial feeding, and other beekeeping methods. Latterly, due to the growing problem of Varroa infestation of bee colonies, breeding programs also consider traits such as hygienic behavior, the growth of Varroa infestation, etc. In Russia, the selection of bees is aimed at obtaining strong colonies that are highly productive in honey, winter-hardy, resistant to diseases, possessing high egg-laying queens, etc. Recently, the genotype-environment interaction and its influence on honey bee health have been of particular interest. These studies demonstrate the relevance of breeding sustainable bee populations and lines adapted to local conditions. This will preserve the diversity of bees, prevent their death, and ensure sustainable productivity and adaptation of bee colonies to environmental changes. In traditional breeding programs, animals are selected and evaluated based on their phenotypic traits and using pedigrees. Such analysis is very labor-intensive, subjective, and considerably time-consuming. Bee selection is complicated by polyandry, male parthenogenesis, free and random mating of queens, death of mated drones, etc. Although the potential of classic breeding methods has not been fully realized yet, modern breeding programs require the use of molecular genetics methods and genomic technologies. The introduction of molecular markers (SSRs, SNP, etc.), sequencing, microarray, and information technology makes it possible to incorporate genetic information into breeding programs and provides more accurate and efficient breeding results. Despite the sequencing of the Apis mellifera genome in 2006, specific genetic markers that could be used in bee selection have not yet been proposed. At the same time, 'Omics' technologies have made it possible to identify various molecular markers (QTL, SNP, RNA, and proteins), which theoretically can be used for the selection and improvement of bee breeds. Quantitative trait loci (QTL) have now been identified, which is associated with queen fertility, disease resistance, and various types of behavior, including hygienic behavior and Varroa-sensitive hygiene in bees. Considerable research interest is aimed at creating bee populations that are resistant to diseases, primarily var-roosis as the biggest threat to global beekeeping, and developing methods for assessing the complex behavior of bees and their effective selection. To assess associations with honey production, gentleness, hygienic behavior, and resistance to the Varroa mite, a high-density SNP chip was developed. It can be used in genomic selection of honeybees and for Genome-Wide Association Studies (GWAS). The successful use of Marker-Associated Selection (MAS) in beekeeping has been demonstrated, namely, DNA markers associated with royal jelly productivity (genes of the mrjp family) have been developed. In 2023, the first study was conducted to estimate the breeding value of a bee reference population based on queen genotyping and it showed that genomic selection can be successfully applied to bees. The use of bee gut microbiome data as markers of colony health and viability in breeding programs is discussed. Thus, honey bee breeding, including molecular selection, provides an increase in the genetic and adaptive potential of existing breeds and the creation of new lines and ecotypes of bees, highly productive and adapted to certain natural and climatic conditions. Selection of honeybees contributes to the development and intensification of beekeeping. Even though the development of DNA markers of productivity, adaptability and resistance to diseases will open up new prospects for genetic selection and provide a significant advantage in time, issues related to the improvement of the classical system of bee selection currently remain relevant. The article contains 4 Figures, 1 Tables, 105 References. The Author declares no conflict of interest.

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