Presentation to 2002 Bay of Plenty Field Day
Presentation to 2002 Bay of Plenty Field Day
by David Yanke, Daykel Apiaries
Any way, Why Should We Bother Importing Genetic Material?
Now that I am into my 3rd different decade of trying to introduce Carniolans into this country, I’ve asked myself that question many times over the years, and sometimes it has been difficult coming up with a convincing answer, but not so since the 11th of April 2000.
All of our lives changed that day, and so has our beekeeping. We are now 2 years post varroa, and I know we had to have time to recover from the shock of its’ arrival, time to grieve for the loss of our varroa freedom, and time to come around to accepting life with varroa. But, it is now time to get on with it. One thing is for sure though, we all know a lot more about varroa now than we did 2 years ago.
We know that varroa likes it in NZ, at least the parts where the mite has made itself at home so far. Conditions here are perfect for varroa, a climate and flora that encourage an extended brood rearing period, and we keep yellow bees that take little encouragement to maintain significant brood areas virtually all year round. To effectively manage varroa, we have to change that, and because(except for the worse) we can not change our environment, then we have to modify the bees we keep.
Now with Varroa, we have to work harder, we have to work smarter, and we have to work with bees that make all the effort worth while. Managing varroa seems straight forward enough- we have an arsenal of effective mite-killing chemicals(at least for now), and a range of biotechnical controls at our disposal- it seems a simple matter to treat, or inflict some fancy hive management on the mites, and then carry on business as usual.
It is not that simple though. Beekeepers are struggling to effectively control the mites. For most of us, even before the mite arrived, there were hardly enough hours in the day to do the beekeeping that needed to be done, and now with mites, we definitely need more hours in the day. It may get easier as we pass through into the chronic phase, but then we will have chemical resistance looming. It is a struggle, and it is hard to look forward to our beekeeping future with any great optimism. Varroa has definitely taken the fun out of beekeeping.
Fortunately, there is a very bright light at the end of this gloomy tunnel, and that light is varroa tolerant bee stocks. I believe that one day, varroa tolerance breeding will give us the ultimate answer to the mite. Overseas, there have been many years of trial and error work going on in this area, and in the case of the bees from the Far East of Russia, the bees have been doing their own tolerance breeding for decades. We are in the fortunate position of being able to take advantage of those efforts.
What Exactly is Varroa Tolerance, and How Do We Breed for It?
Quoting directly from Mark and Cliff’s manual- Varroa Tolerance is the ability of a honey bee colony to co-exist with an infestation of the mite. I won’t keep quoting from the manual, and instead suggest you read that section on varroa tolerance for yourself- not only that chapter, read the whole thing. What I need to say though, is that varroa tolerance is matter of degree ranging from non-tolerance to total tolerance where mite populations never reach damaging levels. Obviously, totally tolerant bee stocks would be the goal of any breeding work, but even small increases in tolerance especially if it were progressive would make any efforts well worthwhile. Like most things in life, varroa tolerance breeding is easier said than done, and a lot of other truisms apply as well- Like- ‘There are many ways to skin a cat’, and ‘No Pain No Gain’.
Varroa Tolerance gets complicated because there are several mechanisms both behavioural, and biological which contribute to varroa tolerance. These include Hygienic, and Grooming behaviour; and the biological traits of Brood Attractiveness, and the SMR trait- the Suppression of Mite Reproduction. These traits have been shown to be usefully heritable, and if effective selection criteria are used, in a properly designed breeding program, progress can be made in any of the traits selected for. Besides these known mechanisms of varroa tolerance, the different racial characteristics of European Honey Bees can enhance varroa tolerance. For example, our yellow bees play into the hands of varroa with their behaviour of maintaining significant brood areas for most of the year, and their propensity to rob and drift doesn't help as well. We could significantly enhance the varroa tolerance of our bees by simply changing the race of the bees we keep to, for example, Carniolans which generally have a more spiked brood rearing seasonal profile, as well as generally, robbing and drifting less then Italians. These different racial characteristics could enhance varroa tolerance by reducing the seasonal reproductive potential of the mites, and by reducing the potential for inter-colony movement by the mites.
When we do get around to setting up a varroa tolerance breeding program, it will face the same problems as those faced by every honey bee stock improvement program that has come, and, unfortunately in most cases, gone before this. Honey Bee populations are very tricky things to do breeding work with. They are like a rubber band, and as you try to pull them in one direction, they are always trying to snap back to where they were. Queen breeders, tragically, usually spend their entire working lives endeavouring to breed better bees only to retire, and pass on stock which is virtually unchanged from what they started with.
There are several reasons for this - starting with the fact that most of the traits we are selecting for are complex behavioural traits with each involving many genes. This is not simple Mendelian genetics, and we are not working with the single gene characteristics of garden peas. Besides the genetics, there is the bizarre mating behaviour of the the virgin Queen, which multibly mates with up to 20 drones, while flying a considerable distance from her colony. This means that a colony whose performance we are trying to evaluate is a very complex beast made up of up to 20 sub-families. As well, environmental influences on the behaviour and performance of a colony make it difficult to sort how much of what we are seeing is environmental,and how much is genetic.
Add to this, the mechanism of sex determination, where sex is determined by multiple variations or alleles of a single gene, at a single locus. The drones we see in hives have developed from unfertilised eggs, which is an unusual occurrence in animals, but not in bees and wasps, and the process is called parthenogenesis. This means that drones carry only one set of chromosomes, and are said to be haploid. Queens and workers, like most things, have 2 complete sets of chromosomes- one from the male parent, and one from the female parent, and they are said to be diploid. When the egg is fertilised, if 2 different alleles or variations of the sex determination gene come together, then a female develops, either a worker or a Queen, but if 2 of the same allele come together, then a male develops. These Diploid Drone’s are cannibalised shortly after they hatch, so we never see them, so in effect it acts as a lethal gene. As I said, there can be up to 19 of these sex alleles in a population. The more sex alleles present, the less likely 2 of the same will come together at fertilisation.
The problem this creates for bee breeders is that when we apply selection pressure to a population with the aim of increasing frequency of the genes responsible for the trait we are selecting for, we are also messing with the frequency of the sex alleles. Most breeding reduces variation which means sex alleles will be lost, and as the number reduces, the per centage of non-viable brood increases helping create the rubber band effect.
As well, honey bees are susceptible to Inbreeding Depression, which is the dark flip-side of hybrid vigour, which is more properly known as heterosis, which is when the offspring perform significantly better then the best parent. It occurs when the per centage of loci, or locations along the chromosomes which are taken up by 2 different variations of a particular gene increases. When there are different alleles of the gene at a loci, it is said to be heterozygous, and when there are 2 of same allele it is said to be homozygous. So increasing variation in a population is likely to increase heterozygosity, which is likely to result in heterosis, which is good, while the loss of variation is likely to increase homozygosity, and create the negative impact on performance known as inbreeding depression, which is bad, and which is why if you married your first cousin you wouldn’t expect your kids to be Olympic athletes.
So the trick, and the secret to sustainably breeding better bees is to use a breeding model which lets you effectively apply selection pressure to a population, and thereby increase the frequencies of the those good genes, while having as little impact as possible on the overall genetic variation in the population. It isn’t easy though, in fact, when all this is considered it is amazing that any progress can ever be made, but it can.
There are several breeding models that can lead to stock improvement, but they all battle the rubber band effect, and once the breeding efforts cease, any gains are soon eroded away. That realisation has to be remembered when we contemplate any varroa tolerance breeding project, whether it involves imported genetic material or not. IF there is not an undertaking to maintain and improve the stock at least in the medium term, then it is probably not worth even starting. So instead of talking specifically about importing tolerant material, we should be talking how that material will be used in an ongoing tolerance breeding program.
How should that program be structured? How should it be funded? and How will the stock be made available to the industry?
I believe it has to have the structure of a Closed Population Breeding Program, the Page-Laidlaw model. This type of program sees a test population established from carefully selected foundation stock. Matings are controlled using Instrumental Insemination. The test population, with a minimum size of 100 colonies would be managed and evaluated under commercial conditions with a minimum, or no mite treatment regime. The 15 best performing Queens would be selected as breeders. Drones, then virgins would be reared from these breeders. The virgins would be inseminated with the pooled semen collected in equal amounts from the drones reared from each of the breeders. Once these Queens were laying, they would be introduced into colonies to reestablish the test population.
For the first few generations, and from then on whenever deemed worthwhile, the semen would probably be imported. After the breeding work to reestablish the test population, a second round of breeding work would be carried out where virgins would be reared from the 2 best performing breeders. Drones would have again been reared from all the breeders, and used for the inseminations. These inseminated Queens would be how the material would go out to the industry. For the program to be viable in the long term, it would have to be commercially viable as well. No matter, whether it was managed privately, or by something, like HortResearch, it would have to be able to generate a profit from the breeder sales. Programs surviving on the goodwill of government or industry live on borrowed time. I visited Ohio State University last year at this time, and spent time with Sue Cobey, who runs the New World Carniolan program there. I also met Joe Latshaw who is a partner in Ohio Bee Breeders. Both of these projects could be models for what we would be trying to do here. While OHB isn’t specifically a varroa tolerance program, Joe works with a couple big commercial beekeepers who select breeding stock under commercial conditions. From that breeding stock, he produces inseminated Breeders, both Carniolan and Italian breeders, for sale back to the industry. Sue Cobey manages the NWC program, which she was starting in California, when I worked for her back in 1984- proof that breeding programs can have a long life. It is now a co-operative effort between a group of commercial Queen Producers and OSU. It is a working model of the Page-Laidlaw Closed Population Breeding program. Again, it supplies Carniolan Breeding stock back to the co-operating Queen producers, and in the case of Kona Queens, because Hawaii is still mite free, semen is used to maintain their Carniolan Breeding stock. When I was back last year, I spent a few days working with the NWC’s. They were beautiful bees to look at and to work, and even though it was bee work, it felt like a holiday. She hadn’t treated for anything- mites,AFB,EFB or hive beetle since the Spring before. They have never treated NWC’s for tracheal mites. I saw nothing but healthy bees, and healthy brood, and one dead small hive beetle on a bottom board. There is no reason that one day we to couldn’t have bee stocks that cope as well with the pest and diseases our bees face here.
So those are my views on why and how we should approach varroa tolerance breeding program here in NZ, and, as I said, we would be very foolish not to take advantage of the work that has been done overseas.
The aim of any importations should be stock improvement. Stock improvement as I described earlier, requires that effective selection pressure be applied, while at the same maintaining enough variation, and a sufficient number sex alleles to avoid the rubber band effect. The conclusions of the new Risk Analysis for importation of Genetic Material leave us with only semen importations as the only workable way to source genetic material from overseas, which is not such a bad thing. Semen is not only inherently safe, but, also, the best way to import genetic material if the goal is achieving the objective of stock improvement. Semen, if it is carefully sourced, and Pooled before the inseminations is an excellent breeding weapon in the fight against the rubber band effect.
You pool semen by bringing together all the semen to be used for the inseminations, diluting it in a physiological saline solution with powerful antibiotic cover. Once the semen is all diluted in a test tube or syringe, it is thoroughly mixed until it is totally homogeneous. The semen is then recovered by centrifuging. All the Queens inseminated with this homogenised semen then receive an identical genetic dose, even though that semen carries enormous variation, including probably all the sex alleles found in the stock it was collected from. Because the male parent contribution is in effect identical, it means that any variation you see is the result of the Queens contribution, and this makes the selection criteria you use work much more effectively, while having minimum effect on the overall variation in the stock.
Finally, I would like to address the concerns that some have had about the impact genetic material imports could have on our present bee stocks. I am more than a little touchy about this subject, because I have had to defend what seems to me so obvious, so many times over the years, against some absolutely outrageous claims by those opposed to any new stock coming into NZ. It feels sometimes that I have knocked myself silly banging my head against fortress NZ. I have struggled to come to terms with the kiwi psyche that results in this fortress mentality, some in our industry have, and why it is such a different attitude to what the Aussies, and most other developed beekeeping countries have when it comes to stock importations. Sure, up until the arrival of varroa, we had an enviable bee health status which was, and still is worth protecting, but the opposition was never about the pest and disease risk posed by importations. Even the most outspoken opponents accepted that the importations could be done safely. The opposition was all about the negative behavioural impact the imports would have on our bee stocks. It was as if our present bee stocks were totally unique, and disaster would befall us if we were to tamper with them. I don’t believe this is the case at all, and all evidence I have seen seems to support this. I have been through this process of answering the critics twice in a formal way. Once, when the risk analysis for the existing IHS was done, and then again, when a declaration was required from ERMA declaring the obvious, that Carniolans were not a ‘New Organism’. In both cases, International experts were consulted, and thorough literature searches carried out. Remember, all the European races are now well distributed around the world, so there is a lot of international experience about the impact of these introductions on beekeeping in other countries to call on. None of the arguments of the opponents were found to have any substance. In fact, for the ERMA application, Peter Barrett, of ‘The Immigrant Bees’ fame was able to document historical carnica importations into NZ, and then of course, there are the well-founded rumours of illegal Carniolan and Caucasian Importations in more recent years, so even NZ has survived Carniolan importations in the past. The fact that we do not see carnica type bees today is proof that unless the imported stock is maintained it will be swallowed up without trace by the existing gene pool. Our bees are nothing new under the sun. Our yellow bees perform pretty much like yellow bees do everywhere, and our black bees perform pretty much like Dark European bees do in other parts of the world. Remember the rubber band effect, if honeys bees have a physical appearance which is true to a particular race, then they are very likely, to behave true to race as well.
The 2 races we have could not be more different from each other. During the evolution of Apis mellifera, as the bees moved west towards Europe and Africa from there origins in Asia, they branched apart with one branch moving west and down into Africa to overwhelm that whole continent, while another branch moved north and west into South Eastern Europe. Our Italians, along with the Carniolans, belong to this northern branch, while our black bees, the dark European bee of western Europe shares its’ evolutionary past with the North African races after crossing back into W. Europe when there was a land bridge at Gibraltar. While Carniolans and Italians are very closely related, with Carniolans being described as the grey version of the Italian, our black bees are a whole different kettle of fish. It seems incredible to suggest that our black bees are more closely related to the African races then they are to our yellow bees, but it is true. When you work with them, or try to breed yellow bees true to their race in their presence, then it is easier to believe. So we have this situation where we already have one race at each end of the racial spectrum. One of the best, in our Italian bees, and undoubtabley, the worst of the European races in our black bees. Their only redeeming feature is their hardiness, but then that works against us as well, because it is why they exist ferrally as well as they do. They are always impossibly nervous, usually nasty, produce little honey, and have little resistance to brood diseases, especially chalkbrood. They give darker bees, or any bee they cross with a bad name. This bi-racial situation we have in New Zealand means that we can expect no new surprises from any importations. All beekeepers will get from the importation of new stock is choice, something we should have had long ago.