The overall goal of this research is to develop and use genetic resistance or tolerance of honey bees to biotic agents, and to devise management strategies to improve the quality of queen honey bees. This will enhance the economic value of the nation’s honey bees for pollination, honey production, overwintering and hazard resistance. Over the next five years we will focus on interrelated projects with the following objectives: Objective 1: Identify and evaluate traits, strains, and stocks for improved honey bee health, e.g., improved immunity, tolerance, or resistance to Varroa and tracheal mites, the fungi Nosema and chalkbrood, and viruses. Sub-objective 1A: Evaluate the potential for viral resistance. Sub-objective 1B: Establish and characterize genetically and functionally distinct lines that differentially respond to Nosema. Sub-objective 1C: Evaluate the potential of worker brood to suppress reproduction by Varroa. Sub-objective 1D: Determine the effect of Varroa infestations on honey bee behavior. Sub-objective 1E: Evaluate immune and stress related responses in selected honey bee stocks. Objective 2: Characterize genetic and physiological aspects of important traits, strains, and stocks and their interaction with biotic and abiotic stressors. Sub-objective 2A: Characterize the chemical ecology of VSH to aid the development of a practical selection method. Sub-objective 2B: Understand the genetic basis of Ascosphaera apis (chalkbrood) resistance observed in RHB larvae. Sub-objective 2C: Genomic sequencing of multiple stocks of honey bees. Sub-objective 2D: Differential responses to Nosema in honey bees. Objective 3: Conduct traditional and marker-assisted breeding and develop management tools for improved bees. Sub-objective 3A: Develop and use improved methods to evaluate Varroa-resistant phenotypes. Sub-objective 3B: Determine management methods using ionizing radiation to increase honey bee colony fitness. Sub-objective 3C: Evaluate autogrooming as a common resistance mechanism towards tracheal and Varroa mites. Sub-objective 3D: Use traditional and marker-assisted selection programs to improve honey bees with VSH-based resistance. Funding will be used in support of Objective 3: Conduct traditional and marker-assisted breeding and develop management tools for improved bees. [NP305, Component 2, Problem Statements 2A and 2B] Objective 4: Improve knowledge of the biology, physiology, genomics, and behavior of pests (i.e. mites and the small hive beetle) that may be useful for improving their management. Sub-objective 4A: Elucidate the Nosema infection process. Sub-objective 4B: Understand effects of resistance level on Nosema infection across honey bee life stages. Sub-objective 4C: Identify new methods to limit SHB population growth in honey bee colonies.
The health and availability of honey bees (Apis mellifera) have been diminished by multiple biological problems, most notably the parasitic mite Varroa (V.) destructor. Other important threats include fungi (Nosema spp. and chalkbrood), viruses, small hive beetles and tracheal mites. Some of these interact and result in mortality described as colony collapse disorder (CCD). The major goal of this project is to mitigate these threats by finding and selecting for genetically based traits of honey bees that confer resistance to the biological problems. Scientists also will improve management techniques and describe pest biology related to control. Most research targets V. destructor. Efforts that build on our prior work with Varroa-resistant honey bees include using knowledge about Russian Honey Bees to find new traits that enhance resistance, and to improve selection methods. Honey bees with Varroa sensitive hygiene are undergoing traditional and molecular-marker-assisted selection. Marker-assisted selection would be a valuable tool to overcome the difficulty of phenotyping this trait, and increase the capacity to select and breed Varroa-resistant bees. Novel traits for Varroa resistance also are being sought. New selection of honey bees will target Nosema ceranae and Deformed Wing Virus because these pathogens are thought to contribute significantly to colony losses. Research with Nosema, viruses, tracheal mites and chalkbrood will culminate in development of molecular markers for resistance factors. Management research will expand promising preliminary findings about queen and drone health associated with the irradiation of comb in mating colonies The products of this research -- knowledge and technology -- will strengthen integrated pest management strategies for controlling honey bee pests and diseases. This in turn should lead to better profitability for beekeeping and crop pollination.
The project currently is in its fourth year of active field research. Excellent progress was made on advancing selection for resistance to deformed wing virus. Parents with high and low susceptibility were chosen last year as the first selected generation, and were propagated for progeny to be evaluated for further differential responses to the virus. There was steady progress on in-house research measuring impacts of varroa mites on activities and physiology of workers and drones, measuring effects of irradiating combs on drone fitness, developing genomic and transcriptomic databases for small hive beetles, developing a genomic sequence database for several types of commercial bees, detailing inputs of honey bee immunity at individual and colony levels, evaluating candidate genes related to varroa-mite resistance and evaluating physiological biomarkers to detect insecticide exposure in honey bees. Research on selection of honey bees for differential responses to Nosema (three project subobjectives) was largely halted because of poor progress with this refractory pathogen. New research began on novel approaches to control small hive beetles (e.g., by using endotoxins from Bacillus thuringiensis). Lingering vacancies in three scientific positions, three technical positions and one Postdoctoral Associate position resulted in termination or delay of 8 of 16 subobjectives in the in-house project. Among ongoing collaborations occurring in Fiscal Year 2017, breeding in a public-private partnership to enhance varroa-resistant bees showed marked improvement of resistance in a commercial operation. Other ongoing collaborations involve efforts to improve preservation of semen for a new honey bee “genebank” (with USDA-ARS and university partners), and evaluating insecticide exposure to bees in the Upper Midwest (with university and industry partners). New collaborations were begun on identifying exposure and risks to honey bee health in a longitudinal field trial (with industry and university partners), searching for molecular markers related to varroa-mite resistance (with an international research institute), determining sublethal impacts of varroa mites and deformed wing virus (with USDA-ARS and USDA-APHIS partners), seeking chemical signals related to varroa sensitive hygiene (with university partners), evaluating the potential threat posed by Tropilaelaps mites (with international university partners) and examining spatial patterns of varroa-infested brood as a sampling tool (with international university partners).
1. A review of the biology of and potential threat from tropilaelaps mites from Asia. ARS researchers at Baton Rouge, Louisiana, reviewed the ecology, life history and management of tropilaelaps mites to provide an overview of the threat that this exotic parasite could pose to U.S. honey bees and pollination services. The review shows that tropilaelaps could be a bigger danger than varroa mites, which currently are the most significant threat to bees. The information affirms the need for U.S. agriculture to be vigilant in addressing the threat posed by tropilaelaps mites, to develop information to more fully understand the mites, and to investigate means to counteract the potential harm from the mites.
2. Genetic diversity enhances immune response of individual of honey bees. Honey bee colonies are known to be more resilient to diseases when the genetic diversity is high, in part because of behavioral responses of adult bees in the colony. ARS researchers at Baton Rouge, Louisiana, and collaborators showed that greater diversity also benefits the colony because of less variable innate immune responses among the individual bee larvae. This finding underscores the import role that proper mating of honey bee queens plays in promoting the health of honey bee colonies.
3. Insecticide sensitivity in honey bees is affected by genetic background and age of bees. Increased attention on the potential harm of agricultural insecticides to honey bees has led to increased scrutiny on methods of how insecticides are tested. ARS researchers at Baton Rouge, Louisiana, found that responses to common insecticides are affected by the genetic background and the age of the commercial stocks of bees being tested. The results can be used to help in risk assessments of different genetic types. They establish baseline information for future assessments and suggest that standardizing testing protocols would be beneficial.
4. Knowledge of gene expression in small hive beetles could lead to control of this pest of honey bees. Small hive beetles commonly cause loss of honey bee colonies, stored honey and wax comb in warm regions of the United States. ARS researchers at Baton Rouge, Louisiana, and collaborators examined expression of the genes of the beetle and deposited the findings in a public database. The information is being used as a foundation for further exploration of potential species-specific, molecular-based control measures that may reduce the hazard to honey bees from both the beetle and the insecticides currently used for beetle control.
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