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About Germplasm and Breeding
Like other managed livestock, there are a wide variety of managed honey bee breeds available, from around the world. Examples you may have heard are 'the Italian bee' or 'Hygienic bees'. The traits of these bees can be selected for preferences of the beekeeper. Honey bee genetics and reproductive biology are complex and pose a challenge for breeding. A queen naturally mates in a flight with 10-20 drones. She stores the sperm for several years and fertilizes eggs as she lays them. This robust genetic system allows maximum diversity within a colony, and it also makes selection of traits a slow and noisy process. Many projects focus on bee breeding for specific traits (including disease or Varroa resistance). As a tool for breeding, the ability to store germplasm in a honey bee genetic repository (cryogenic gene bank) has recently been developed for the first time at Washington State University. WSU supplied germplasm to and collected from western US queen producers. Diversity represents raw material for future breeding and selection programs by the beekeeping industry to improve disease and parasite resistance.
Current Germplasm and Breeding Research
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Developing a Functional and Sustainable Honey Bee Legacy Germplasm Repository at Washington State University Principal Investigator: Steve Sheppard, Washington State University, 2013
Current populations of honey bees in the US represent descendants of importations made primarily between the time of early European colonization and 1922. In 1922, the US Honey Bee Act restricted further importation of honey bees into the United States and, with very few exceptions; subsequent breeding efforts have been conducted using only genetic material derived from pre-1922 US populations. The WSU bee research program has been actively importing source population honey bee germplasm from Europe for breeding purposes since 2008. In 2012, with funding provided by Project Apis m, WSU established the world’s first honey bee genetic repository and initiated the use of this technology to conduct backcrosses between domestic honey bees and cryopreserved genetic material from Old World source populations of honey bees. In addition to providing novel genetic material to the WSU bee breeding program, genetic material supplied to queen producers in the western US led to a significant increase in genetic diversity in honey bee populations maintained by these queen producers. This was in contrast to the continuing decline in diversity measured in stocks that did not incorporate new germplasm. In summary the outcomes of the initial three years of support from Costco (PAm) included:
Establishment of a functional germplasm repository. The repository currently houses germplasm from 5 honey bee subspecies from the Old World, several USDA and a number of commercial genetic breeding lines. The liquid nitrogen storage system is compatible with industry standards and represents a continuing investment for the future of honey bee breeding and stock improvement.
Demonstration of impact of germplasm distribution from the repository and the WSU bee breeding program to commercial queen producers supplying more than 1 million queens to the US beekeepers. The decline in genetic diversity in commercial honey bee stocks measured over three decades was reversed in the breeding populations of queen producers supplied with novel germplasm.
Reintroduction of the “Caucasian honey bee” (A. m. caucasica) to US beekeepers. This honey bee is well-adapted to cold conditions, such as those found in its homeland in the Caucasus Mountains, and represents an alternative strain of honey bee for beekeepers in northern climates.
Introduction of a new honey bee subspecies (A. m. pomonella) to the United States. This honey bee is endemic to the Tien Shan Mountains of Central Asia. The Tien Shan Mountains are the area of origin for apples and this new honey bee is being introduced as a potential improved apple pollinator. The germplasm was collected in 2015 and the purity of the breeding line is currently being improved through backcrossing. Release to commercial queen producers should begin in 2017.
Inclusion of the honey bee into the USDA-National Animal Germplasm Program, in Ft. Collins, CO. This Program is associated with the world’s largest germplasm storage facility for animals and plants of agricultural importance. Based on the successful establishment of the WSU honey bee germplasm repository, we were asked by NAGP Director Dr. Harvey Blackburn to help establish a “species committee” for the honey bee. This committee is responsible for setting priorities in honey bee germplasm acquisition and the protocols for the dissemination of genetic material to “end users”. Given the expertise developed over the past three years, we were also asked to travel to major queen producers in CA, cryopreserve honey bee semen from their genetic stocks and make the initial “deposits” of honey bee germplasm into the USDA-NAGP. Improved understanding of the genome of the honey bee has moved bee breeding marginally closer to the use of marker-assisted selection protocols. In addition, the development of cryopreservation in honey bees now makes it possible to incorporate “progeny-testing” into selective breeding programs. Our intention is to make use of these new options to improve the efficiency and progress of honey bee breeding, while continuing to incorporate standard “trait-selection” approaches in our bee breeding program. At the same time, integration and collaboration of the breeding efforts with the queen producers, who supply the bulk of the honey bee genetics available in the US, remains an important aspect of our Program.
Novel Varroa Controls/Breeding Principal INvestigator: Steve Sheppard, Washington State University, 2015
Modern Tools for Selecting Disease-Resistance Traits in Honey Bees Principal Investigator: Leonard Foster, University of British Columbia, 2016
Most of the losses of honey bees in recent years are attributable to pests and pathogens. The most important of these, by far, is the parasitic mite Varroa destructor but others, such as Nosema spp. and Paenibacillus larvae, are also widespread. We have chemical methods for controlling these pests and pathogens but these are undesirable for several reasons: 1) there is growing pressure from consumers to reduce or eliminate the use of pesticide, particularly in food production, 2) they can also harm the bees and/or humans, 3) the target organisms can develop resistance, reducing the effectiveness of the chemicals. The best solution for managing bee health is to select for bees that have innate resistance to or an ability to live with mites, Nosema and other pathogens. During the past seven years we have identified molecular markers of hygienic behaviour and are now poised to apply them to both guide selective breeding for this important disease-resistance trait and to understand the mechanisms underlying it. In a preliminary study, we have been able to show that selecting for hygienic behaviour using marker-assisted selection is as effective as selection using the standard liquid nitrogen freeze-killed brood (FKB) test. Additionally, the bees selected in this way appear to not lose other economically important traits (e.g., honey production) but are far better equipped to deal with diseases like American foulbrood and the Varroa mite than ‘average,’ unselected bees. For this project, we are proposing to work with a handful of early-adopter bee breeders from Western Canada to start applying these tests in their own operations to select for disease resistant bees. These experiments will start enriching for an important disease-resistance trait in the Canadian honey bee population, leading to a population that requires less intervention to control disease.
WSU Queen Principal Investigator: Steve Sheppard, Washington State University, 2015
Breeding for Improved Varroa-Resistant Bee Stock To Support Honey Bee Health, Crop Pollination, and Honey Production Principal Investigator: Robert Danka, USDA - ARS, Baton Rouge, 2016
Managed honey bee colonies are critical for pollinating food, fiber and oil crops worldwide. While the need for pollination services is growing, health threats to honey bees also are growing. The single largest culprit in colony losses is the parasitic mite Varroa destructor. Varroa mites feed on the blood of bees and vector viruses and bacteria as they feed. Left unchecked, mites will kill most honey bee colonies. Most beekeepers use chemical treatments to control mites and keep colonies alive. This is not ideal because chemical treatments are costly and laborious, have variable results, can leave chemical residues in honey and wax, and have sublethal effects on the bees themselves. Mites also routinely develop resistance to chemical treatments; the single most effective miticide used by commercial beekeepers (Amitraz) may soon lose its effectiveness. A more sustainable approach to managing Varroa mites is through development and use of mite-resistant bees. The best characterized mechanism of resistance is the behavioral trait called Varroa sensitive hygiene (VSH). Bees that express VSH can detect reproducing Varroa on immature bees and remove those infested bees, ensuring that the mites do not successfully reproduce. VSH appears to be present in honey bee populations worldwide at low levels. The trait is genetically inherited and its expression can be increased through selection. It was discovered and initially developed by the USDA during 1996-2007 from a small number of colonies that were selected exclusively to amplify the VSH trait, not for productivity.
Bees with this trait were made available by USDA, in hopes that breeders would incorporate it in the industry’s 2 million queens annually produced, but the rate of adoption by beekeepers has been slower than anticipated. This is likely because other commercially-important characteristics of the bee need improvement to meet practical beekeeping efforts in crop pollination and honey production. Another hampering factor is that measuring expression of the VSH trait is beyond the technical practices of almost all bee breeders. Doing so requires intensive brood census and microscopy to measure Varroa mite reproduction.
To continue pursuit of commercial adoption, in 2008, USDA began to develop a new population named “Pol(inator)-line”, merging the VSH trait with desirable characteristics by crossing the original VSH bees with bees in several commercial beekeeping operations, and then selecting the best performing colonies. Pol-line bees have relatively high Varroa resistance on average, but as expected, this second generation VSH population is still quite variable in both mite resistance and beekeeping performance. The critical next step to resolving the variation of these traits, will be possible using strategic crosses of lines by instrumental insemination. Queens crossed with a single drone (single drone insemination or SDI), can be used to refine the breeding population and fix the resistance trait, and then naturally mated queens from these lines will be evaluated for production traits. Combining these techniques in a year-round breeding climate of Hawaii, where isolated mating areas allow control of the drones available, is an optimal situation for accelerated progress.
Comparison of US Honey Bee Genetic Lines for Queen Production and Pollination Efficiency Under Field Conditions Principal Investigator: Steve Sheppard, Washington State University, 2016
There is evidence that honey bee subspecies that have evolved in mountainous/temperate regions fly at lower temperatures than subspecies originating from warmer regions. A majority of the US commercial breeding stock is derived from Apis mellifera ligustica, a subspecies native to the Italian peninsula. The subspecies evolved in a generally warm “Mediterranean” climate. Previous importations of a number of other subspecies are reported in the literature, but most fell out of favor with US beekeepers or were lost due to founder effects. There remains a small percentage of queens in the US sold as “carniolian queens” originally derived from A. m. carnica, a subspecies endemic to the Alps Mountains. With genetic material imported by WSU over the past 8 years, coupled with the ability to backcross progeny using cryopreserved semen, we have been able to largely reconstruct several subspecies here in the US. Two of these, A. m. caucasica and A. m. carnica, have been made available recently to commercial queen producers and are beginning to be more widely distributed to beekeeper customers. As a result, we now have an opportunity to directly compare among subspecies for traits such as mating flight success and foraging behavior during inclement temperatures. Coincident with this new opportunity to directly compare subspecies and unique US breeding lines we now have the capacity to delineate differences that could have significant impacts on crops that depend on honey bees as the main source of pollination. There are a number of crops in the US that can suffer reduced yields due to poor pollination that results from decreased bee flight time during cold or inclement weather through bloom. This project will, for the first time, provide empirical data to test the long-held hypothesis that honey bee subspecies from mountainous regions fly/pollinate at lower temperatures than subspecies from warm/arid climates. At the other end of the spectrum there are high value seed crops that bloom during the heat of the summer that can also show reduced yields caused by a lack of pollination, because at a certain temperature honey bees divert the foraging force from pollen collection to water collection when temperatures are too hot. It would be logical to hypothesize that honey bees adapted for hot/arid climates might be better pollinators in those conditions than bees derived from mountainous areas. A better understanding of the characteristics of the available breeding stock in the US is essential as we face unknown climatic shifts that have major impacts in our agricultural system. Findings from research described above have the potential to change pollination strategies and demands for specific honey bee “types”. It might be, that for increased pollination security/insurance there is value in stocking orchards/fields with a mix of distinct honey bee genotypes to improve crop yields in years of abnormal weather. Specific Objectives: 1.Compare 2 Old World subspecies and 3 commercial lines for mating success in early season (temperate/inclement weather) queen production. 2.Compare 2 Old World subspecies and 3 commercial lines for pollination efficiency under various weather conditions (cold weather fruit and nut pollination and hot weather seed crop pollination) 3.Compare 2 Old World subspecies and 3 commercial lines for overwintering survival, productivity/vigor and Varroa tolerance.
Comparative Characterization of Virus Content and Resistance in Genetic Lines of US Honey Bees Principal Investigator: Olav Rueppell, University of North Carolina, 2017
This research combines two principal objectives that relate a comprehensive evaluation of virus resistance of available US genetic lines of bees to their natural virus profiles. This will inform beekeepers and queen breeders about the risks and potential of different genetic stocks with regards to viruses, one of the major contributors to the ongoing honey bee health crisis. The first objective is to survey queens from different genetic lines for viruses and characterize the quantity and genotype of their viruses by sequencing. We will also assay queens and eggs from these queens to evaluate the potential of the queens to act as infection routes for viruses into uninfected apiaries. Our second objective is to compare the resistance of honey bee workers of different genetic stocks against IAPV and DWV in controlled laboratory experiments. The quantification of resistance assesses a central trait for colony health that needs to be incorporated into breeding efforts. Our central hypothesis of this proposal is that genetic lines of honey bees in the U.S. vary in their virus content and resistance and that these two parameters are important for improving the existing successes in breeding honey bees for sustainable apiculture. Virus screening is only practiced sporadically and largely ignored by commercial queen breeders. Our study will demonstrate that queens may provide important transmission routes for viruses across the nation, and that disease screens need to be adopted by breeders. Secondly, our study will quantify the relative resistance of some prominent genetic lines of honey bees to two of the most important honey bee viruses under standardized laboratory conditions. This study will thus clarify whether virus resistance contributes to the overall health of these strains and provide insights in how the breeding of these lines can be improved in the future.
Understanding Semiochemical tools for Natural Varroa Control Principal Investigator: Olav Rueppell, University of North Carolina, 2017
Protecting Queens for Improved Colony Productivity Principal Investigator: Jeffery S. Pettis, University of Bern, 2017
Queen quality and availability are major concerns of beekeepers today. Problems arising from queen rearing, mating, shipping, or exposure to pathogens and pesticides may result in lower queen health. One poorly studied factor that can affect queen’s performance and longevity is the viability of the sperm in the queen’s spermatheca. In an ongoing project supported by PAm, we are assessing the effect of exposing queens to temperatures encountered during shipment, and the effect of temperature-induced low sperm viability on queen and colony performance and productivity. Results to date show that queens can be exposed to temperature extremes during shipment and this in turn can reduce the viability of the sperm they stored in the spermatheca. Further, a colony level field experiment (Guarna) showed that queens exposed to high and low temperature demonstrate lower performance and their colonies are less productive both in terms of bee population and honey productivity. Finally, recent reports have shown that chemical exposure can have an effect on queen sperm viability and affect queen performance. We hereby propose to develop and evaluate strategies to reduce exposing queens to temperature extremes and to chemicals while increasing our understanding of the effect of these risk factors on queen health and colony productivity. Our findings will guide recommendations to queen producers, improve conditions for queen shipments and provide new management options for beekeepers prior to, and after, queen introduction in their colonies. The main aim of our proposal is to increase queen health and performance by improving shipping conditions and education of shippers and beekeepers about the sensitivity of live queen shipments to temperature extremes. We propose to define strategies to: a) Improve queen shipment and management conditions to reduce exposure to temperature extremes. b) Initiate an employee education program within USPS and UPS to improve the handling of live queen bee shipments. Currently, queens are commonly shipped long distance, particularly to northern US and to Canada, where local queens are generally not available early enough in the year to respond to the spring demand for queens. Our previous research has demonstrated that both hot and cold temperature extremes can be experienced by queens during shipping. Even cold temperatures in August which can only be explained by temperatures in the cargo hold of planes. Thus, an employee education program of the safe handling of live queens by the two shippers, USPS and UPS could go a long way to solving this problem. Additional education programs for beekeepers and even queen breeders may be possible at the beginning and end of the shipping process.
Completed Germplasm and Breeding Research
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Bee Lab Support Principal Investigator: Sue Cobey, University of California, Davis, 2007
Seeking Brood Signals for Hygienic Behavior Principal Investigator: Kaira Wagoner, Universtiy of North Carolina, Greensboro, 2014
Miticides used for protection against Varroa are harmful to bees and lose effectiveness as Varroa become resistant. While other control strategies such as physical mite removal and use of essential oils do exist, they have many limitations that compromise efficacy, including increased labor for the beekeeper, temperature vulnerability, and minimal differences between target and non-target lethal dose concentrations. One especially promising solution to the problem of Varroa is the augmentation of hive resistance through the selective breeding of hygienic behavior. Hygienic hives have been shown repeatedly to exhibit reduced mite and disease loads compared to unselected hives. However hygienic lines do not currently serve as sustainable alternatives to chemical Varroa control, as chemical treatments are still required to control severe mite infestations in hygienic hives. Reasons for lack of sustainability include non mite-specificity of selection processes and time and expense required for current selection assays. The former is of crucial importance as the olfactory trigger for hygienic removal of mite-infested and other live brood is significantly lower than that of dead brood currently used in selection assays. Thus the threshold for olfactory response needs to be lower for mite-removal than it does for removal of freeze-killed brood. Varroa-resistant bees do not require the time and expense of new compound development and approval, and do not lead to development of resistance or pesticide exposure and accumulation in bees, humans or ecosystems. While the majority of studies of hygienic behavior mechanisms have focused on sensitivity and modulation of adult olfaction, recent evidence indicates the importance of brood signals in triggering hygienic behavior. I will research brood signals and the effects of mite pre- exposure on grooming and hygienic behavior to facilitate development of novel strategies for mite-specific selective breeding. By improving understanding of and capacity to enhance mite resistance in honeybees, this research will contribute novel and sustainable alternatives to use of harmful miticides improving honeybee, human and environmental health worldwide.