The COLOSS Research Network for Sustainable Bee Breeding

The COLOSS task force “Research Network for Sustainable Bee Breeding” (RNSBB) aims to improve honey bee well-being by developing and disseminating comprehensive breeding strategies that include colony vitality and the conservation of locally adapted populations. The foundation is that studies on honey bee health must also consider the bees’ genetic origins and how they interact with the surrounding environment.

Recognition of Natural Variation across the Native Range

The Western honey bee, Apis mellifera L., has a considerable variability at the sub-specific level, reflecting the wide variety of ecosystems in its native range in Africa, Europe, Western and Central Asia. Description and classification of the A. mellifera subspecies were initially performed using morphometric methods. The comprehensive monograph “Biogeography and taxonomy of honeybees” (1988) by Friedrich Ruttner (1914–1998) is still considered an important reference manual for honey bee diversity. More recently, increasing evidence from molecular methods has added to the picture, with tests for subspecies diagnosis of a bee sample now available at a commercial level. Cooperation among RNSBB members has led to advancement in this area of study, both in terms of description and characterisation of honey bee populations (Puškadija et al., 2021; Uzunov et al., 2014; Zammit-Mangion et al., 2017) and of tools with which to identify and classify the subspecies (Momeni et al., 2021; Muñoz et al., 2015; Nawrocka et al., 2018). These are important pre-requisites for the protection of natural honey bee diversity and tools that beekeepers and beekeeper associations are increasingly demanding, as awareness of the importance of keeping locally adapted bees grows.

Honey Bee Populations Are Adapted to Their Environment of Origin

Indeed, research carried out within this task force highlights that the safeguard of bee diversity has an economic relevance for beekeepers, beyond its scientific and ethical value. A three-year study on a pan-European level, the so-called “GEI experiment” (Genotype Environment Interaction) clearly showed that locally adapted populations are better suited than imported ones to cope with prevailing environmental conditions and health threats, and thus, to survive (Figure 1) (Büchler et al., 2014; Meixner et al., 2015). The experiment was conducted within the COLOSS COST Action, between 2009 and 2012, and involved 16 European honey bee lines belonging to the subspecies A. m. carnica, A. m. ligustica, A. m. macedonica, A. m. mellifera, and A. m. siciliana. It was established with a total number of 621 colonies located in 21 bee yards in 11 European countries. To investigate the GEI, the local strain of bees was tested together with bees of at least two “foreign” origins at each location. Colony management was performed according to local practices, but colonies were all started according to a standard protocol. Across all apiaries, no chemical treatments against Varroa destructor were administered to present a selection pressure and stress condition under which to test the colonies. The test protocol (Costa et al., 2012) involved measurements of colony survival and development, productive and behavioural traits and presence and prevalence of pests and pathogens. Data collection was performed according to uniform methods that were developed and discussed during regular meetings and training sessions organised by different members of the group across Europe. Throughout the experiment, partners were frequently in contact to exchange opinions and for local adaptation of the management techniques. The outcome of the study showed that it is worthwhile to continue work towards conservation of locally adapted honey bee populations. The complete results have been published in a Special Issue of the Journal of Apicultural Research (Meixner, Büchler, et al., 2014).

Figure 1. Map of experimental apiary sites in the Genotype Environment Interaction experiment. Insert: survival curves of colonies in the experiment, classified according to origin of the bee strain (local or non-local), from Büchler et al. (2014).

Selective Breeding of Local Stock to Achieve Conservation of Natural Diversity

The outcome of the GEI experiment and participant experiences in the field of breeding led to the involvement of several RNSBB members in a large European Union (EU) funded research project on “sustainable management of resilient bee populations”, the “SmartBees” project. In this project, the protocols for testing vitality parameters that had been discussed and tested within the GEI experiment were applied on a practical scale, as beekeeper organisations were actively involved. Breeding programs were initiated in areas and for populations where no previous breeding activities had occurred, giving new impulse and value to subspecies not traditionally considered useful for commercial beekeeping. The ultimate aim of this approach, known as “conservation by utilisation”, is to reduce the introgression and hybridisation pressure on native subspecies by increasing attractiveness of local bees for beekeepers, thus decreasing their incentive to import foreign queens. Within this same project, a comprehensive characterisation of honey bee diversity of Europe was performed based on a huge collection of honey bee samples across the continent, representing nearly all European subspecies. This immense collection effort was only possible thanks to the contacts and exchange of information and knowledge within the RNSBB. Genomic analysis of these samples ultimately led to the development of a powerful molecular tool enabling rapid subspecies diagnosis of honey bee samples of unknown origin (Momeni et al., 2021).

Identification of Resistance/Adaptation Traits to Improve Resilience

It is well known that the mite V. destructor is one of the main challenges faced in beekeeping, and that vitality of a colony must include its ability to cope with infestation by this parasite. In the GEI study, V. destructor infestation was identified as the primary cause of colony death. Differences in V. destructor infestation levels across the experiment were mostly due to environment; however, within each location, colonies with lower infestation levels survived longer (Meixner, Francis, et al., 2014). Investigating honey bee resistance mechanisms to V. destructor, developing methods for their evaluation, and assessing whether and how they can be incorporated in breeding programs is one of the task force’s objectives. Thus, to provide baseline data for regional breeding programs, we initiated a common study to evaluate the presence of the resistance trait “Suppression of Mite Reproduction” (SMR) in different European honey bee populations. The study was conducted in 2015 and 2016 by 17 laboratories (mostly part of RNSBB) in 13 European countries (Mondet et al., 2020). A total of 414 colonies, distributed in 68 apiaries and managed by the participating institutes or by partner beekeepers, were evaluated using a common protocol that was drafted during RNSBB workshops. The tested colonies belonged to local populations of the European subspecies of A. mellifera (A. m. carnica, A. m. caucasica, A. m. cecropia, A. m. iberiensis, A. m. ligustica, A. m. macedonica, A. m. mellifera, A. m. carpatica), and to commercial hybrids such as Buckfast and hybrids of A. m. carnica, A. m. ligustica, and A. m. mellifera. Thus, they were representative of European honey bee diversity and commercial beekeeping reality. The descriptive analysis of the complete dataset resulted in an overall average SMR score of 33%, with 16% of the colonies showing an SMR score ≥50%. From a practical point of view, this study showed that the trait is present in European honey bee populations, making efforts for its selection worthwhile. From a methodological point of view, the large body of data collected allowed us to estimate the variability in the SMR score depending on the number of single-infested brood cells per colony that were analysed. To assess the SMR score with an acceptable reliability and feasibility, we determined that a minimum of 35 cells should be investigated.

Field Tests and Providing Evidence for Policy Makers

When the Agriculture General Directorate of the EU Commission decided to fund a study to better understand the state of the art of honey bee breeding, with the aim of producing V. destructor resistant stock, the existing collaboration within RNSBB proved essential in the drafting of a successful proposal: the EurBeST study occurred between 2018 and 2021 and explored the status of the EU market of honey bee genetic material, the structure of EU honey bee breeding activities and possibilities for increasing the V. destructor resistance of commercially available strains. As a first step, an assessment was made of the existing V. destructor resistant stock, with a review of the mechanisms standing behind the resistance (Le Conte et al., 2020). To provide reliable data regarding the performance of resistant stocks, specific lines were compared under commercial conditions in five case studies, including traditional traits and V. destructor resistance (VSH, SMR, REC, hygienic behaviour). Results showed that strong genotype-environment interactions affected many traits, highlighting the importance of local adaptation. Local lines produced more honey, but the test lines had fewer mites at the end of the study. Some lines from long-term selection programs combined good productivity and improved V. destructor resistance.

Outcomes and Perspectives

The research performed within the task force and by task force members highlights the strong need to preserve the honey bee’s natural adaptation to the local environmental conditions. To achieve this, we must encourage regional breeding efforts and raise awareness among policy makers and regional authorities to support the conservation of local strains of bees.

The expertise and experience held by RNSBB task force members (scientists and apiculturists involved in honey bee breeding, population genetics, taxonomy, characterisation studies, conservation initiatives) combined with the task force working approach, which includes cooperation, exchange of ideas and mutual support, in a positive and friendly atmosphere, provides an excellent basis for achieving the ambitious aim of promoting sustainable beekeeping.

Cecilia Costa*
CREA Research Centre for Agriculture and Environment, Bologna, Italy
Cecilia Costa https://orcid.org/0000-0001-9985-2729*Email: [email protected]
Marina D. Meixner
LLH Bee Institute, Kirchhain, GermanyMarina D. Meixner http://orcid.org/0000-0002-7785-4894Email: [email protected]

Acknowledgement

Support from the COLOSS network has been invaluable in terms of enabling and encouraging exchange of ideas, meetings, training sessions and workshops.

Disclosure statement

No potential conflict of interest was reported by the authors.