Meaningful contributions towards enhancing the economic value of the nation’s commercially managed honey bee populations can be achieved through identifying, characterizing and breeding more robust bees. The proposed 5-year plan focuses on synergistic projects (Fig.1) that capitalize on genetic and breeding approaches with the following objectives: Objective 1: Identify and evaluate traits, strains and stocks for improved honey bee health. Sub-objective 1A: Understand the mechanisms of viral transmission and resistance or tolerance to reduce impacts of infection through selective breeding. Sub-objective 1B: Evaluate genotype-dependent nutrient efficiency in commercial honey bee stocks. Sub-objective 1C: Evaluate genotype-dependent nutritional stress resistance in commercial honey bee stocks. Sub-objective 1D: Characterize the impact of genetically based variation in vitellogenin -- the primary honey bee storage protein with roles in immune function, oxidative stress resistance and lifespan -- on colony and reproductive (queen and drone) health and productivity. Sub-objective 1E: Identify and characterize genetic and physiological mechanisms of pesticide resistance in honey bees. Objective 2: Characterize genetic, physiological and behavioral aspects of important traits, strains and stocks. Sub-objective 2A: Examine patterns of genetic diversity and loci under selection in United States honey bee breeding populations, with a focus on stocks exhibiting high VSH activity. Sub-objective 2B: Elucidate the interaction between individual and social immune defenses. Sub-objective 2C: Improve understanding of the biology of the VSH trait. Objective 3: Conduct traditional breeding or marker-assisted selection of honey bees. Sub-objective 3A: Ascertain the effect of inbreeding on genetic diversity across the honey bee genome to support breeding and maintaining health of breeding populations. Sub-objective 3B. Assess genetic diversity at the sex locus of commercial breeding populations of honey bee stocks developed by USDA, ARS HBBGPL. Sub-objective 3C: Determine the potential usefulness of a simple hygiene assay as a selection tool to predict VSH-based mite resistance in honey bee colonies. Objective 4: Develop management tools for improving honey bee health. Sub-objective 4A: Identify and characterize genetic differences in honey bee response to introduced dsRNA, and test for correlations with viral infection and resistance. Sub-objective 4B: Improve understanding of the flight activity of Russian honey bees during almond pollination. Sub-objective 4C: Evaluate the efficacy of a microalgae platform to improve honey bee colony performance and health. Sub-objective 4D: Determine the sublethal effects of fungicides on honey bee health. Sub-objective 4E: Assess sustainability of Varroa control methods.
Objective 1: Identify and evaluate traits, strains and stocks for improved honey bee health. [NP305, Component 2, Problem Statements 2B and 2C] Sub-objective 1A: Understand the mechanisms of viral transmission and resistance or tolerance to reduce impacts of infection through selective breeding. Hypothesis 1A.i: Honey bee resistance to viruses varies with virus type and inoculation route in addition to genotype and life stage of the bees. (Led by M. Simone-Finstrom with K. Ihle)
This is the first report for the project 6050-21000-016-00D (Using Genetics to Improve the Breeding and Health of Honey Bees), which began in March 2020. Progress was made in research objectives that fall under National Program 305, Component 2, Bees and Pollination. The goal of this research is to enhance the economic value of the nation’s commercially managed honey bee populations through identifying, characterizing and breeding more robust bees while concurrently informing management practices. Research by ARS scientists from Baton Rouge, Louisiana, progressed related to identification and evaluation of traits, strains and stocks for improved honey bee health (Obj. 1). Progress was made by ARS scientists from Baton Rouge, Louisiana, in understanding resistance and tolerance traits associated with viral infection and how different honey bees stocks and genotypes differentially respond to Deformed wing virus, Israeli acute paralysis virus and chronic bee paralysis virus (Obj. 1A). This work involves several projects including collaborative efforts with ARS scientists from Baton Rouge, Louisiana, Louisiana State University, University of North Carolina at Greensboro, and University of Olomouc (Czech Republic). Additional work has begun to develop a novel RNAi delivery system to mitigate honey bee pathogens (in-house) and on potential chemical-based viral treatments (collaboration with Louisiana State University). In an assessment of a possible new trait for future breeding efforts, three honey bee stocks were examined to assess influence of honey bee genotype on the efficiency of food conversion (Obj. 1B). Results indicated that some stocks have more variable responses as compared to others, which is an important consideration for a future selection program. With regard to understanding the genetic variation in pesticide detoxification capabilities (Obj. 1E), investigations by ARS scientists from Baton Rouge, Louisiana, began into substrates that can be used as reliable surrogates of insecticide detoxification by esterases, and the relationship of esterase activity inhibition on insecticide toxicity. Progress was made by ARS scientists from Baton Rouge, Louisiana, in the characterization of genetic, physiological and behavioral aspects of important traits, strains and stocks (Obj. 2). Samples have been collected for follow-up work to ARS scientists from Baton Rouge, Louisiana, earlier large-scale genomic sequencing effort examining genetic diversity across seven commercial honey bees stocks in order to expand those initial results and conduct more detailed analysis on specific genomic regions (Obj 2A). Efforts to specifically mitigate Varroa mites and support various resistance traits in honey bees continue to be a focus. An evaluation of “social apoptosis”, or brood fragility, as a mechanism for Varroa resistance in selected stocks of honey bees was completed (Obj. 2B) and suggested that this could be a potential factor particularly in the Russian stock. Analysis by ARS scientists from Baton Rouge, Louisiana, is ongoing on the response of honey bees to developing drones parasitized by Varroa mites (Obj. 2C), but results suggest that there has been no selection for increased hygienic response to infested drone brood in the Russian stock. Efforts to support traditional breeding or marker-assisted selection of honey bees progressed (Obj. 3). Genetic diversity at the complementary sex-determiner (csd) locus was assessed in Pol-line and Hilo bees (Obj. 3B). Allelic data are currently being used to inform breeding decisions for both stocks. An assay using the chemical ecology that regulates expression of hygienic behavior is being tested (Obj 3C). Collaborators from the University of North Carolina at Greensboro developed this tool to evaluate the response of bees in field colonies to chemical stimuli related to Varroa sensitive hygiene. Work by ARS scientists from Baton Rouge, Louisiana, is also ongoing to identify molecular markers related to expression of the trait of Varroa sensitive hygiene, including approaches using candidate genes (in-house), whole-genome sequencing and marker discovery using both gene expression and sequence information via “eQTL” (in collaboration with the University of Missouri). Breeding for productive, Varroa resistant bees continues in a public-private partnership in which bees selected by the Unit for Varroa sensitive hygiene form much of the founding population for a new stock, called Hilo Bees. Research in collaboration with the University of Minnesota and commercial beekeeper cooperators has continued to clarify the role of propolis in honey bee immunity and its potential benefits in beekeeping management, and to breed bees with improved health founded on social immunity. Progress was also made in projects related to the development management tools for improving honey bee health (Obj. 4). In an effort to develop a new nutritional supplement, work was conducted by ARS scientists from Baton Rouge, Louisiana, to evaluate the use of microalgae as an alternative nutrition source for bees (Obj 4C). Results indicated that in controlled, caged settings this microalgal diet performs just as well as a pollen-based diet based on several metrics. Preliminary field trials have also been conducted in collaboration with cooperating beekeeping operations. Baseline data were established for a nationwide assessment of the resistance of Varroa mites to amitraz in commercial beekeeping operations (Obj. 4E). Results documented by ARS scientists from Baton Rouge, Louisiana, showed that some Varroa mite populations do demonstrate resistance to amitraz that is associated with treatment failures, however resistant populations appear to be related to specific operations and amitraz use patterns and not necessarily geographic area. In subordinate projects, research was conducted by ARS scientists from Baton Rouge, Louisiana, on the influence of propolis deposition on insecticide sensitivity and detoxification activity in honey bees, and to determine the presence of pesticides in propolis collected from colonies across different landscapes. Two longitudinal field trials of two years each are yielding information about the biotic and abiotic health threats to honey bees in commercial beekeeping operations. These trials were conducted in collaboration with ARS scientists from Baton Rouge, Louisiana, and Louisiana State University. Progress was made in collaboration with North Carolina State University and University of Pennsylvania to clarify the genetic determinants of queen quality.
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