Breeding Beneficial Bees

Adapted from a talk presented by Tom Glenn at the EAS meeting at Cornell University, August 2002

The buzz word of the day is globalization. But globalization has not been kind to bees or beekeepers. I'm not talking so much about honey prices as I am about the spread of mites and diseases worldwide. Never in the history of beekeeping has there been a more important goal for us to aim for. That is to solve the mite and disease problems our bees are having without harming the bees or contaminating the honey and wax. The recent problem with contaminated Chinese honey should be a wake up call, if ever there was one.

Many good people around the world are attacking the problem from different angles. Some are looking for more benign chemical treatments. Others are testing various integrated pest management systems. One component of an IPM system is the use of genetically resistant bees.

A genetic solution would clearly be the most efficient and economical way to go. The elimination of the need for treatment would not only cost less for labor and material, it would reduce harmful effects to the bees and free us from anxiety over contamination of honey and wax. Once developed, resistant bees cost no more raise than susceptible bees.

R. Buckminster Fuller's Dymaxion map projection. A new way of looking at the world.

Just as this picture of the world gives us a different perspective of the world. Today I want to give you my view, from a queen breeder's perspective of how we can use genetically resistant bees to help solve disease problems.

This is sort of a love triangle that we find ourselves in. It started with the plants and bees millions of years ago. They developed a perfectly cooperative arrangement where the bees give the plants a sexual thrill in exchange for the nectar and pollen the bees need to survive.

Man came into the picture much later as a hunter gatherer. He was a predator of the bees, hunting them and killing them in the process. But he eventually learned that it was much more productive to cooperate with the bees by helping them survive and thrive. For the last ten thousand years, since agriculture began, we've been selecting and influencing both plants and bees. The bees we have today are the result of these interactions.

Today as beekeepers we are right in the middle of this cooperative triangle. We now realize that whatever we can do to maintain the health and productivity of the bees is in our own best interest. Breeding bees to enhance their own immunity to diseases and mites is what we intend to do.

Back in 1980 Dr. Walter Rothenbuhler wrote this article for ABJ on how best to improve the country's bees. His message was that it needs to be a cooperative effort on the part of all types of beekeepers in the industry. Allowing each group to do what they do best. The honey producers and pollinators are the bottom line, so they ultimately must test the stock under real life conditions.

The scientists are expert at sorting out the effects of different variables. And in beekeeping we have nothing but variables. They are the best ones to plan what tests to do and to analyze the data.

The queen rearing industry is ready made for this type of bio control. We are very efficient at taking a few excellent breeder queens and propagating them by the thousand. We are also very good at distributing them to beekeepers in every corner of the country.

In this country we don't have an official bee improvement program. But over the years these links, either formally or informally have formed. So we have sort of a self organized system which is ultimately determined by the free market, by what type of bees beekeepers choose to keep.

To think about bee breeding, we need to think about bees on 3 levels. I call this the 3 bee concept. The first level is that of the individual. And like all animals, each bee is a complete organism in it's own right. Each bee is the product of it's own genome and it's interaction with the environment. There are probably between 10 and 20 thousand genes in the honeybee genome. Every bee contains a unique combination of these genes.

But honeybees are never found living alone, they are always found living as part of a colony, what biologists call a superorganism. The colony is the level that we beekeepers usually think about bees on. Since a queen mates with from 10 to 20 drones, a colony is really a collection of subfamilies. Each subfamily having the same mother, the queen, but different drones for fathers. I want to draw the analogy of how bees are like a game of poker. Just as each individual card is unique, so are bees. But cards like bees go together, and some cards make for better poker hands than others. In just the same way, some subfamilies work better together than others. And anyone who has had more than one beehive knows that some are always more productive than others.

The next level is the interbreeding population.This can be as local as all the hives around your apiary, including the feral, hobby and commercial hives. Or you can think of the gene pool of the entire country. Or even in these days of globalization, the gene pool of the entire world.

An interesting property emerges at the level of population. In a large interbreeding population, the frequencies of the genes tend to remain stable. The entire science of population genetics is built around the simple but counterintuitive fact that gene frequencies stay the same except under the influence of selection, migration, mutation, or random drift. Likewise for the entire deck of cards, though they get shuffled around, all the cards stay the same.

If we wanted to improve our chances of getting good poker hands, we might think about stacking the deck with extra aces. And if we want to improve the chances of getting better colonies, we can stack the gene pool with the genes that produce the traits that we want in the bees.

Individuals and colonies are temporary, but it's at the level of population that lasting changes can be made. But the population is made up of colonies, and colonies are composed of individuals. It is at the level of individual, the queen and the drones she mates with, that all the work must start at.

So what tools do we have to stack the deck with? So far we have three specific traits which have proven themselves useful, hygienic behavior, tracheal mite resistance, and suppressed mite reproduction SMR (Now renamed VSH for Varroa Sensitive Hygiene). And we have instrumental insemination as a tool to try to get all of these traits into the same bees, which is what we really need.

At these meetings you've heard or will hear the world's experts talk about each of these traits so I'll just touch lightly on each one.

Probably the greatest advance in human health was Louis Pasteur's discovery in the 1800s , that many diseases were caused by microbes. With this key bit of information, doctors realized that they should wash their hands between patients and that surgical instruments should be sterilized. The whole world began to protect their water supplies from contamination. In other words people began to have better hygienic behavior.

So it's not surprising to find that other animals, including bees have also found the beneficial effects of better hygiene. Bees have always been known for their cleanliness and good housekeeping, and this is a form of hygienic behavior. But here we are talking about a very specific trait that allows the bees to detect diseased brood behind a cell capping, to uncap it and to remove the infected brood before it can fester and spread billions of spores around the hive. It has been found to be controlled by two recessive genes, one for uncapping the cell and one for removing the brood.

This trait is very effective, I can personally attest to this. I used to have an annual problem with chalkbrood, I could count on having an outbreak every year. Since I've been using hygienic bees the last few years, chalkbrood has virtually disappeared, I rarely see a mummy anymore. This is what has sold me on the idea that genetic resistance really works. So you can use the presence of chalkbrood in your bees as an indicator of how hygienic your bees are.

Hygienic behavior was originally studied as a mechanism against American foulbrood (AFB). With tetracycline resistant stains of foulbrood now cropping up around the country, hygienic behavior is more important than ever.

It's also been found to be effective in keeping varroa populations in check. Though it is probably not the end all in varroa resistance, it is certainly an important part of our arsenal

How does hygienic behavior enhance productivity. Quite simply, when the bees don't have to waste their time and energy raising brood that dies from disease, they have more time to collect honey.

It's interesting to study a timeline of the development of the idea of hygienic behavior. It began back in 1935 when O.W. Park first studied resistance to AFB. It wasn't until 1942 that Woodrow identified the mechanism of uncapping and removing diseased brood. In the 1960-s, Rothenbuhler did a series of experiments that revealed the two recessive gene model that is widely accepted. Later Steve Taber and Martha Gilliam refined methods of selection and helped popularize the trait. I owe Steve a debt of gratitude for turning me on to hygienic behavior through his writings. More recently Marla Spivak has extended her studies to the effect on varroa and also the neurobiology of the behavior. She has also done a lot to encourage breeders to select the trait in their own bees as well as providing seed stock to the industry. Finally around 2000, AFB has developed resistance to tetracycline. One has to wonder why it has taken almost 70 years for such a good idea to have gotten into mainstream beekeeping. If we had spent more time decades ago developing hygienic stock, we would have saved ourselves millions of dollars in treatment. Our bees would be resistant to chalkbrood and foulbrood, and we would have fewer varroa mites. We would not be scrambling now to find another antibiotic to fight resistant foulbrood. Let's hope it doesn't take another 70 years to utilize the other genetic tools that we have.

Tracheal mites have been in this country since the mid 1980s. At first our bees were quite susceptible. Probably some of the bee importations from Europe, like the Buckfast and Yugoslavian bees that were adapted to resist tracheal mites, helped introduce this trait into our bees. Some people feel that they are no longer a major problem, but they continually crop up as a major factor in winter mortality.

There has been some impressive work done by USDA scientist Dr. Robert Danka that show how the resistance mechanism works. By restraining various legs of the bees, Dr. Danka proved that it was the middle leg that grooms the mites away and prevents infestation of the trachea. He also found that this grooming trait was controlled by dominant genes.

A trait that is beneficial and controlled by dominant genes will tend to be naturally selected for. But because it is dominant, that means that the recessive susceptible genes get carried along for the ride and can show up in generations down the line. This is probably why it keeps cropping up as a problem. So as breeders we need to keep a constant selection pressure on the trait. Dr. Danka has formed an important link with the queen industry by providing a testing service with Edwin Holcome, to help breeders select for the trait.

The latest trait we have to work with is Varroa sensitive hygiene, or VSH. This trait was developed over the course of the last seven years by Dr's. Harbo and Harris of the USDA bee lab in Baton Rouge. This behavioral trait is triggered when the mites begin to reproduce. Probably an olfactory cue tells the worker bees which brood cells to uncap and remove bee pupae along with the developing varroa mite family. This very effectively limits the population growth of the mites, to the point where chemical treatments are not necessary.

Several effects have been observed, including the mites not laying eggs, or laying them too late for them to fully develop. Also sperm counts are low in the mated females. Many of the mother mites get caught and die between the cocoon the larva spins and the cell wall.

Dr Harbo believes this naturally occurring trait can probably be found in low frequencies in any population of bees. He also thinks that SMR (now VSH) is an additive trait.

An additive trait is controlled by neither dominant or recessive genes. SMR/VSH is probably determined by more than one gene. So the more of these genes are present, the more of the trait will be expressed. This is lucky for us because by starting with queens inbred for the trait, a breeder can easily import the trait into his stock at the 50% level. So if we are careful, we can keep the good bees we have but add this SMR/VSH trait to them. As time goes on and more drones in the population carry the trait, resistance should become more common in our bees and in feral colonies. The return of the feral bees will be a good indicator of the bees gaining resistance.

Instrumental insemination has been an invaluable tool in the development of all these genetically resistant traits. It's also helpful in controlling the mating so that we can combine all of these traits. But I don't want to mislead you into thinking all the work has already been done, it's really just beginning. Everyone can't keep inseminated queens in their colonies. The battle has to be won with naturally mated queens. Fortunately, I think enough breeders are interested in using resistant stock, that any beekeeper can now find various stocks to experiment with.

The world has changed for beekeepers in the last few years. It's true that we can never go back to the good old days. We have new problems and challenges the old timers could never have imagined. But we also have new tools to work with. We have computers and instrumental insemination. We also have the principles of genetics and a huge body of scientific knowledge about bees to draw on. So I'm confident that if we play our cards right we can solve these problems. In fact I think we are on the very brink of doing so.

I'd like to leave you with a quote from Ralph Waldo Emerson. He said:

"This time, like all times, is a good time if we but know what to do with it."

Adapted from a presentation by Tom Glenn at the EAS meeting at Cornell University, August 2002