2006 Annual Report
1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter?
Problem to be Solved- Honey bees are vital to U.S. agriculture because of their value as pollinators of important crops such as almonds, apples, and squash. Honey has less economic value than the billions of dollars attributed to pollination activities by bees, yet honey provides the major source of income for most beekeepers. Both pollination and honey production require healthy colonies of bees, and honey bee populations in the USA are under constant attack by Varroa destructor, an external parasite of the honey bee. This parasite is the number one problem in the beekeeping industry in the USA and worldwide. Until the late 1960’s, this mite was restricted to southeast Asia as a parasite of Apis cerana, the Asian hive bee. It now has worldwide distribution. If a susceptible colony of bees is not protected with miticide, it dies within two years. Because of chemical contamination issues, cost of treating with miticides, and the ability of these mites to develop resistance to miticides, our long-term solution is to breed honey bees for resistance to varroa.
Objectives- The primary goal of this research is to control the parasitic mite (Varroa destructor) by breeding honey bees for resistance. Our approaches to this problem are as follows:
1. Continue work with suppressing mite reproduction, the suppressed mite reproduction (SMR) trait. Note: New knowledge of the details of this trait has resulted in renaming in 2005 as "varroa sensitive hygiene" (VSH) To improve breeding strategies, we will (1) determine how many genes are involved in the VSH trait (our preliminary data suggest that there are two); (2) determine if the VSH trait is associated with other characteristics of bees; (3) establish the VSH trait into inbred lines; and (4) combine these inbred lines into productive hybrids that are virtually free of mites.
2. Complement the VSH trait by developing another varroa-resistance trait, percent mites in brood (PMIB). Although we have demonstrated that we can achieve almost total resistance to varroa mites with only the VSH trait, it is not prudent to rely on one mechanism for mite resistance. PMIB is the percentage of a mite population that resides in brood cells. The remaining mites in a bee colony are phoretic on adult bees. Although this trait has been associated with lower mite populations and we have already shown it to be a heritable trait of the honey bee, it has not been subjected to selective breeding. Our goal is to select bees for low PMIB and thereby prolong the time that a mite spends on adult bees. Our approach is to isolate, intensify, and evaluate PMIB or possibly another mite-resistance trait that affects mites outside the brood cell.
3. Combine multiple traits. We will combine the VSH trait with other mite-resistance traits and determine if the mite-resistance traits are independent, if they are compatible when bred into the same bee or the same colony, and if their interactions affect mite resistance.
4. Pollination component. Because pollination is the primary economic benefit derived from the beekeeping industry, we will evaluate pollination-related foraging performance of new bee stocks to help judge the suitability of the bees as commercial pollinators. Newly identified foraging attributes may be used in breeding programs; foraging detriments will be corrected by management or breeding.
Customers, products, and impact. We expect to produce additional mite-resistance traits of the honey bee and to improve the VSH (varroa sensitive hygiene; previously known as SMR = suppressed mite reproduction) trait that we released to the bee industry in 2001. New traits will be offered to the beekeeping industry as well as new hybrid combinations of the VSH trait and the VSH trait in combination with other mite-resistance traits. When free-mated to unselected drones (standard procedure for commercial queen rearing), queens with two mite-resistance traits may be more resistant to mites or less variable in their level of resistance than queens with the VSH trait alone. Also, with two mite-resistance traits in each queen that we supply to queen breeders, we will double the rate at which mite-resistance genes are added to our commercial and feral populations of honey bees.
Our immediate customers are commercial queen producers who will propagate and sell queen bees from the genetic material that we provide to them. Our ultimate customers are beekeepers (commercial, sideline, and hobbyist) who purchase mite-resistance queens from queen producers. Those beekeepers will benefit from having stocks of honey bees that are productive and resistant to mites. Our distribution of mite-resistance traits should help beekeepers and other bee scientists select their bees for mite-resistance traits, and the propagation and selection of these beneficial genes should increase levels of mite-resistance genes in our nationwide population of honey bees. Increased frequency of mite-resistance genes will make it easier to find and produce mite-resistant bees and should hasten the return of our feral population of bees. Feral honey bees not only provide free pollination service to gardeners and backyard fruit growers, but their countless numbers and adaptation to every corner of our nation make them our most valuable resource for honey bee germplasm.
2.List by year the currently approved milestones (indicators of research progress)
a. Test effects of screening and ventilation on mite-resistance of bees and the behavior of mites
b. Make initial selection for a low percentage of mites in brood (PMIB) trait
c. Measure cotton yield increase with honey bees
d. Establish test and select four lines with the SMR trait and begin to establish inbred lines for hybrid breeding.
a. Conduct a backcross experiment to determine the number of genes involved in the VSH trait and to determine if poor brood production is related to the SMR trait
b. Continue to select for bees with a low PMIB
c. Measure effect of increased visits to rabbiteye blueberries
d. Continue to select four lines with the SMR trait
e. Obtain test lines; verify QTLs and develop markers
a. Evaluate potential mechanisms to explain the PMIB trait
b. Test resistance of combined VSH and PMIB traits
c. Continue to test and select inbred lines and test hybrid combinations
d. Determine the physiological basis for ovary development in queens
e. Make backcrosses, conduct chalkbrood resistance field trials, and develop markers
f. (New milestone) Develop more efficient methods for evaluating the VSH trait
a. Initial release of the PMIB trait to the beekeeping industry
b. Enhance the combined traits into breeder queens that will be economically desirable to beekeepers
c. Assess foraging of VSH hybrid x commercial Italian stock
d. Test VSH hybrid combinations and begin initial release of hybrids to industry
e. Adapt artificial insemination procedures to enhance oviposition of queens
f. Determine microsatellite patterns
g. (New milestone) Develop more efficient methods for evaluating the VSH trait
h. (New milestone) Search for new sources of Italian-stock bees with VSH
i. (New milestone) Begin to create and phenotype VSH colonies to be used in genotyping studies
a. Determine the number of genes involved in a trait of the honey bee that affects PMIB
b. Evaluate enhanced hybrid bees that have genes for both the VSH and PMIB traits
c. Continue testing VSH hybrid combinations
d. Finish DNA marker tests and compare with chalkbrood scores to locate QTLs and linked microsatellites
4a.List the single most significant research accomplishment during FY 2006.
Single significant accomplishment FY 2006
Backcrossing genetically segregating drones with high VSH queens yielded colonies with a range of phenotypes for VSH-based varroa resistance. The range of expression showed that bees with the VSH trait did not hygienically remove mite-infested brood if the infesting mite did not reproduce. It also suggests that the easiest way to measure VSH is to measure the frequency of mites that do not lay eggs. Colonies with greater frequencies of non-ovipositing mites apparently have bees with correspondingly greater numbers of genes for VSH.
4b.List other significant research accomplishment(s), if any.
Other significant accomplishments.
We determined that bees with VSH target infested pupae that are between 4 and 7 days postcapping.
4c.List significant activities that support special target populations.
5.Describe the major accomplishments to date and their predicted or actual impact.
Some customers had noticed that colonies with high levels of the VSH trait sometimes had poor brood production. Results from a backcross experiment showed no relationship between the VSH trait and poor brood production or low bee populations. These results suggest that it should be possible to produce a stock that has good beekeeping qualities while it is virtually free of varroa mites.
Field testing showed that bees with the VSH trait apparently removed mites from capped cells. Of the mites that remained, VSH colonies had a much higher rate of nonreproductive mites, 80% vs. 29% for non-VSH colonies. This suggests that VSH bees removed reproductive mites more often than they removed nonreproductive mites. By knowing the mechanism behind the VSH trait, we and other bee breeders will be better able to select for this trait and also separate this trait from other mite-resistance traits.
6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
Scientists from this project addressed beekeepers or scientific audiences at national meetings of the American Honey Producer’s Association (Houston, TX, Jan. 2006), the American Beekeeping Federation (Louisville, KY, Jan. 2006), the American Bee Research Conference (Baton Rouge, LA, Jan. 2006) and a meeting sponsored by the Foundation for the Preservation of Honey Bees (Lincoln, NE, Aug. 2006). Presentations occurred at regional meetings of the Heartland Apicultural Society (Vincennes, IN, July 2006) and the Eastern Apicultural Society (Young Harris, GA, Aug. 2006). We also addressed state beekeepers associations in Louisiana and Mississippi.
The unit scientist participated in a Laboratory Field Day for beekeepers in October 2005.
7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Harris, J.W., Harbo, J.R. 2006. Vsh bees disproportionately remove varroa-infested hosts from the youngest age cohorts of pupae. American Bee Journal 146(5):448
Harbo, J.R., Harris, J.W. 2006. Varroa-infested cells that are not removed by bees with varroa-sensitive hygiene. American Bee Journal 146(5):447-448