Selective breeding of honey bees for multiple traits with a priority on nosema disease resistance

Selective breeding of honey bees for multiple traits with a priority on nosema disease resistance

Summary

During Spring and Summer 2012, 50 new honey bee colonies were started as 3 frame nucs with open mated daughter queens of 3 Instrumentally Insemenated breeder queens from Glenn Apiaries, CA. These breeder queens are from nationally recognized breeding programs to develop mite resistant honey bees. Of these 50, 15 where culled by July 10th, 2012 since they did not build up well in population during June. The other 35 daughter colonies were given the opportunity to build their own combs and populations and overwinter without treatments for mites, nosema disease, bacterial infections, or any other conditions. Of these, 14 died before March 2013. Measures in strength, disease and pest levels were taken periodically from July 2012 to March 2013. These measures were reviewed to select 10 candidate breeder queens from the surviving 21 colonies for 2013, primarily by culling colonies low in population in the face of disease and pest pressure and selecting colonies high in strength. The next step will be to select 4-6 of these 10 to use and repeat the process in 2013-14. The experience from the first cycle, shows that varroa mites and nosema disease are a problem in untreated colonies. A larger pool of test colonies is probably needed to ensure enough potential candidates. Some of the 10 potential candidates for 2013 are large, strong colonies, but high in mites and/or nosema. Fortunately at least 4-6 colonies are low in mites and nosema and should potentially be excellent breeder queens. For the 2013-14 cycle, more colonies will be started as test colonies to ensure a larger pool of strong colonies making it through the winter without treatments.

Objectives/Performance Targets

FORMAT: The objectives planned are stated here with adjustment for the second year in brackets [] afterwards.

The selection program will use standardization of management and blocking on starting date to reduce variation, so that genetic based performance can be measured. Selection will use ranking and elimination schedules.

Over 4 weeks, 20 queens per week (80 total) will be raised from 4 breeder queens incorporating the VSH mite resistant line. Daughter queens will be open mated, ensuring considerable genetic variation. Queens will be selected from each 20 queen group. The mother of each daughter queen will be documented.

[For the second cycle, queens selected in the first will be used. Not enough of my colonies survived through 2012 to be able to make up 80 new test colonies in the first round, but this will be attempted again in the second cycle. More colonies are available for me to use to start new nucs this year.]

First stage evaluation: Daughter queens will be started in small, equal sized colonies with 3 combs. Room for colonies to build more combs will be provided. After a period of 21 days, the new queen should be mated, laying, and all brood will be from the new queen that is being evaluated. Starting measures for frames of bees, brood, drawn comb, and food stores will be measured by proportion of coverage of frames. At 42 days after establishment, all emerging bees should be from the new queen. At 63 days after establishment, colonies will again be evaluated for a change in population and strength. Brood disease will be measured at this time by presence or absence of brood dead in cells. The top 10 performing colonies for each 20 colony group will be retained.

[This tight grouping of 20 colony blocks based on time was not an achievable goal. For the second cycle colonies will be started as possible through spring and summer alternating mother queens for each graft to spread out the variation on starting date among the breeder queens. This was essentially the method used in the first round]

Stage two evaluations: The 40 selected colonies will be sampled for varroa mite levels and Nosema spore levels from natural infection. Infection is historically endemic. Mites will be measured by the sugar roll method outlined by the University of Minnesota. Nosema spore sampling will use the standard hemocytometer method by Cantwell (1970). After three months, mites and Nosema spore levels will again be measured so change in infestations can be determined. Four colonies from each group (16 colonies) with the smallest growth in Nosema spores, and secondarily varroa mites, will be selected. These 16 colonies will be evaluated for hygienic behavior using the freeze killed brood method.

[The numbers selected at each stage will be based on the number of colonies performing at a certain level based on the data instead of arbitrary numbers]

Stage three evaluations. If possible, varroa and nosema treatments will be withheld for these 16 colonies. In spring 2013, these colonies will be evaluated for nosema disease, mites, brood disease, and strength. The top 4 performing colonies based on these measures, and hygienic behavior, will be selected as mothers for queens produced in 2013. The selection process for 2012 will be repeated on new, 2013 queens.

[Treatments were not needed during the first round evaluations. This will be attempted again. Once the first round colonies where evaluated, they were treated for varroa in March 2013 since the evaluation period was then over, mite levels were high for this time of year, and these colonies will be divided up to start new colonies.]

Measures of stock improvement: In 2013, an additional 20 queens will be raised from one or more of the original 4 breeder queens used in 2012, depending on how many survive. These daughter queens will be placed into the evaluation scenario. This will create a reference population of 1st generation daughters to compare with 2nd generation daughters within the same year. This will prevent differences in disease pressure during different years from affecting the results. Statistical comparisons will be made to compare colony measures between generations.

Breeder queen evaluation: all breeder queens used (8) will be evaluated for the same measures to look for correlations with daughters, indicating heritable traits.

[of the original 4 instrumentally inseminated queens planed to be used as mother queens, 1 was culled due to brood disease. A 2nd queen was used to produce several daughter queens, but then was suddenly lost for unknown reasons (not the colony just the queen). So for the original remaining Instrumentally inseminated mother queens 3 and 4 it was decided to not do any measures on these since they were few and not really comparable, being managed as overwintered colonies. They are still alive and daughter colonies from these will be attempted for comparison.]

Accomplishments/Milestones

The objective of selecting productive, potentially parasite and disease resistant breeder queens was achieved for the first season. A measure of varroa mite infestation in all surviving test colonies was conduced in Fall 2012 and Spring 2013. Additional measures were desired, but these 2 measures revealed low levels of varroa mites overall in 2012, particularly for that late in the year. However, the varroa mite population grew greatly over the winter and was likely a cause of colony deaths. The first part of our winter was mild, so brood rearing through winter probably allowed for reproduction of varroa mites. Nosema levels were measured in Fall 2012 and Spring 2013. With nosema as well, the levels were low in Fall 2012 yet grew greatly over winter and levels were high in Spring 2013. Nosema was also likely a cause of some colony losses. More measures of these two pests are planned and achievable in 2013-14 because of the experienced gained in the first round. Four measures of colony strength and 3 measures of brood disease, brood quality, and temperament occurred during the test period. The efficiency of these measures were improved and I’ll be able to do more of these in 2013.

The varroa mites were measured with the powdered sugar shake on 300 bees to report mites per 300 bees. Measures of the amounts of capped brood were taken during the colony strength measures to allow adjusting the mite infestation level to account for the number of mites inside the capped brood. These brood measures are convenient to do when checking for brood disease, but not convenient to do at other times. However, this mite level adjustment based on the amount of brood seems to be unnecessary and prone to error at the precision level used in this project so it will only be done when checking for brood disease. That way, varroa levels can be monitored more frequently and on more colonies. It took a considerable amount of time to gain experience in measuring nosema spores on the low quality microscope available to use. Now I can do the micorscopic work to measure nosema disease more easily so testing more frequently and on more colonies in 2013 is planned. As indicated in the summary, the primary need selection in untreated colonies is for large pool of potential colonies for selection. The variation in colonies seems to be great, so less precision in strength measures are planned for the next cycle, while more colonies and more frequent measures are planned.

Impacts and Contributions/Outcomes

The primary outcome for the first year is 4-6 apparently excellent breeder queens for the following season. The strength and health of these colonies without treatments is promising. Orders have been placed by a beekeepers for 60 colonies started from breeder queens out of this program which will distribute this stock to others. Additionally, a number of beekeepers have placed orders for virgin daughter queens of selected breeders to be able to cross this stock with bees at their own location. This avenue of distribution is being pursued more to be able to potentially distribute 100’s of daughter queens for colonies selected out of this program in the first year. If this market for virgin queens can be developed, 1000’s of daughter queens could easily be distributed since the beekeepers would produce their own mating nucs. Planned outcomes early in the coming year is to summarize some of the numbers collected while measuring colonies in strength, varroa mites, and disease to investigate if varroa mites or nosema spore measures are predictors of either colony population or death in this group of colonies. This will be posted on my website, Rosecombapiaries.com. On the website can also be found the data sheet I use for colony measures and some instruction on methods to breed bees.

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