The State of the
Art of Bee Breeding
"Science is knowing, art is doing, and
common sense is knowing and doing on the basis of experience." Alex
Over the last few years the beekeeping world has been assaulted
by Varroa mites, tracheal mites, and Africanized bees, all of which are
problems best solved through bee breeding.The response of the scientific
community to these threats has been painstaking research into the natural
resistance mechanisms that some bees possess. Today we are confident that
several of these resistance mechanisms are effective and practical to breed
towards. Bee researchers Marla Spivak and Martha Gilliam sum up the state
of the art of breeding for resistance in a recent review of research on
hygienic behavior. "Hygienic behavior of honey bees provides multiple
benefits for beekeepers with no apparent negative characteristics that accompany
the trait......Research has clearly demonstrated the benefits of hygienic
bees. Beekeepers should be using this information to improve bee stock." Bee World (1998)
The rapid spread of the Varroa mite to beehives worldwide
has presented a challenge to bee scientists and bee breeders to develop
resistant stock. Both feral and beekeepers' colonies have succumbed by the
millions, resulting in loss of pollination of crops, gardens, and wild lands.
European honeybees were caught by surprise when the Varroa mite, originally
a parasite of the Asian honeybee, jumped to our European honeybee species.
The European bees, having no experience with this mite have little defense
against the mites. Bee scientists, through careful observation and experiments
have discovered several defense mechanisms that are used successfully by
the Asian honeybee.
- Hygienic behavior - the ability
to recognize and remove mite infested larva.
- Varroa Sensitive Hygiene (VSH) - a varroa specific hygienic behavior.
- Grooming behavior - removing
and injuring mites from themselves or another bee.
- Short brood development period - resulting in less time for mite reproduction on brood.
- Longer time spent on adults -
as opposed to inside brood cells reproducing.
- Today, miticides are widely used, although Varroa is
already showing resistance to these chemicals. Beekeepers long for the
good old days when they were not obliged to put miticides in proximity
of honey, the most natural of foods. Nearly everyone agrees that the breeding
of resistant stock is the best hope for a long term solution to this serious
- Given enough time and in the absence of chemical treatment,
European bees would probably become adapted to Varroa by natural selection,
as the Asian honeybee has. The goal of the bee breeder is to accelerate
this process through artificial selection. This is done by identifying
the bees with the desired characteristics and controlling their mating
to accumulate these traits in a "closed population." Closed population
breeding programs have long been used with great success in the breeding
of dogs, cattle, and other livestock. It has only been relatively recently
that the mating biology, genetics, and techniques in artificial (instrumental)
insemination of bees have been worked out so as to make possible, sustainable
closed population breeding programs.
- Research in the last few years has shown that Varroa
resistant traits also exist in European bees. Through selective breeding,
hygienic behavior and SMR have now been developed to the point of being
in practical use by beekeepers. Today it's encouraging to hear more and
more reports of beekeepers able to return to beekeeping without the use
- The design of a selective breeding program must take
into careful account the genetic peculiarities of honeybees.
- Honeybees have a haplo / diploid reproductive system.
This means males are hatched from unfertilized eggs, so they have no father
and only have half the chromosomes of a female.
- Unlike most animals, each one of a drone's 10 million
sperm are identical clones. Sister bees with the same father share 75%
of their genes. This is far more than the 50% found in other species.
- The queen naturally mates with up to 20 drones, making
the colony a collection of many subfamilies (half sisters with the same
mother, but different fathers).
More about Principles
of Honeybee Genetics.
As queen breeders, our role is to take the information
gathered by university and government scientists, apply it in our breeding
program and then offer our stock to beekeepers. The following are some of
the selection tests we are using in our program. See bibliography for more details.
1. Test for Hygienic Behavior
There are several methods of testing for hygienic behavior.
They all are based on the rate of removal of sealed brood which has been
killed behind the capping. The freeze kill method is the most accurate and
preferred for scientific work. Liquid nitrogen can be used to freeze kill
the brood in a few minutes. Alternatively, a piece of comb can be cut out
of the comb and frozen in a freezer. The pin prick method is less accurate
but more convenient, it's the easiest method to start checking the hygienic
behavior of your bees.
Pin prick method
Cappings of newly sealed brood cells are punctured with
a fine pin to kill the larva beneath. After 24 hours, the number of cells
uncapped and cleaned out are counted and recorded. After several replications
under different environmental conditions, colonies which have cleaned at
least 90% of the cells within 24 hours are considered hygienic. This form
of hygienic behavior has been shown to be a significant factor in resistance
to Varroa, as well as American foulbrood, and especially Chalkbrood. Genetics of hygienic behavior.
1) Mark a cell directly above three groups of seven newly
sealed cells. Use a quick drying paint (e.g. Liquid Paper). Also mark the
2) Kill all twenty-one larva by pricking them with a pin
through the cappings. Use the same hole to prick the larva several times
at different angles.
3) Twenty-four hours later count how many cells are completely
uncapped and cleaned out. Colonies which have cleaned 19 cells (90%) are
"The Hygiene Queen" Marla
Spivak describes a more scientific method using freeze killed brood.
2. Brood Viability
Honeybees can have a lethal gene which can cause spotty
brood patterns. The gene which determines the sex of the bee, is called
the "sex allele" . Each
female has two alleles, one from it's mother and one from it's father. There
are 19 or so different variations of the allele possible (let's call them
A,B,C...S). The egg and the sperm each contributes one allele. If the combination
is different, (e.g. AB, BC, DE, etc.), a female bee results. If two of the
same allele variations happen to occur at fertilization (AA, BB, CC..),
the egg is eaten immediately upon hatching. This special circumstance creates
a male bee known as a diploid drone, which is never allowed to mature in
the hive. This is a cause of what beekeepers know as "shot brood,"
when as little as 50% of the brood survives. Selecting for high brood viability
greatly increases the efficiency and productivity of colonies. Low egg viability
can be a result of inbreeding and loss of sex alleles. Our closed population
breeding program maintains high genetic diversity, thus preventing inbreeding
while promoting solid brood patterns.
How to test the brood viability of a queen.
1) Cut a parallelogram from a card. There should be 10
worker cells per side, enclosing a total of 100 cells.
2) Place template over the most solidly sealed patch of
3) Count the number of empty cells. Subtract from 100 to
get the percentage of brood viability.
4) In this example 100 - 13 = 87% viability. Above 85%
Our first method is a standardized test given to all colonies
in the apiary under the same conditions to be sure gentle temperament is
maintained. After an apiary with many hives has been worked, it is often
impossible to determine which hives the more aggressive bees came from.
A second technique we find useful to separate out any "mean" bees
is to capture them in a black plastic bag. Do this by swinging it's open
end in a figure eight in front of you, this both attracts and captures the
bees. Once captured, the bees can easily be immobilized with carbon dioxide
gas or refrigeration and then marked with paint. After being released these
guard bees can be found at the entrances of the hives which are then culled
from the program because of unacceptable temperament. We select drones and
queens from only gentle, workable colonies.
4. Tracheal Mite Resistance (graphic)
The mechanism of resistance against this mite is as yet
unknown, but it does clearly exist. Recent evidence suggests that grooming behavior as the mites migrate from one bee to another may be a means of control.
Fortunately this trait appears to be controlled by dominant gene(s) and
occurs widely in honey bees.
Thousands of bees are examined to determine which hives
show resistance. A test can also be done by placing newly hatched workers
from various hives among bees known to be infested, for about a week. (Bees
are only susceptible to mite infestation when they are very young, up to
ten days old). The bees are then dissected and mites in the trachea are
counted. Differences in attractiveness or susceptibility to mite infestation
5. Honey Production and Comb Building
Comparisons of honey production and comb building are made
of individual colonies in the same apiary and under the similar conditions.
High honey production results from the right number of healthy bees being
in the hive at the proper time. Factors enhancing health will likely increase
honey production. High honey production using disease resistant stock is
the ultimate goal of our breeding program
Inseminated Breeding Stock
Why use instrumentally inseminated queens
in a breeding program?
Honeybees are the only insect which can be instrumentally
inseminated, allowing bee breeders to have complete control over the mating
of the queens and drones.
Instrumental insemination allows two very powerful procedures
which are not possible with naturally mated queens.
- 1. Queens can be mated to a single drone, simplifying
selection for specific traits.
- 2. Queens can be mated to hundreds of drones, maintaining
Breeding for specific traits using single
- The multiple mating
habits of bees has always been an obstacle to progress in breeding
bees for specific traits.
- To simplify the selection process, queens can be instrumentally
inseminated to single drones.
- All 10 million sperm produced by a single drone are identical
- Queens mated to a single drone produce progeny with extreme
- Genetic consistency and genetic diversity are opposite
ends of a spectrum. One necessarily gives up diversity in trade for "fixing"
any trait in an individual, a colony, or a population.
- This genetic trade-off can be optimized using single
drone inseminations together with mating other queens with large numbers
of drones (supermated).
genetic diversity using supermated queens
- Naturally mated queens normally mate with from ten to
twenty drones on their nuptial flights.
- Oddly enough, the semen carried in a single drone is
more than enough to fill the queen's spermatheca, where sperm are stored
for the lifetime of the queen.
- The queen takes a great risk to gather so much extra
genetic diversity for her progeny, to the advantage of her colony.
- Recent findings suggest that bees of different patrilines
specialize in the various behaviors found in honeybee colonies.
- It is thought that the more genetic options, the more
behaviors will be optimized.
- Using instrumental insemination enables the breeder to
go one step beyond nature and inseminate the queen with hundreds of drones.
- Drones are chosen from colonies expressing desirable
traits such as disease resistance, high honey production and gentleness.
- Semen is extracted from hundreds of drones from many
colonies, mixed together, then used to inseminate many queens. We call
these queens "supermated".
- Supermated queens have very high brood viability due
to the high diversity of sex alleles,
which means more bees in their colonies.
- By maintaining a high degree of genetic diversity the
negative effects of inbreeding are avoided.
- Supermated queens contain many times the genetic diversity
of naturally mated queens. They are excellent as breeder queens in breeding
programs to prevent unintentional inbreeding.
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February 13, 2013