This is not an exhaustive list and its a bit dated. I'm posting it at a request on the chat forum. There is a LOT more that should be in this.
Over the course of several years, I have wished for but never seen a good list of the various traits that can be influenced by a bee breeding program. Following is a list I have compiled of some of the traits of importance to beekeepers. Keep in mind that this is a list of genetically influenced traits, with some comparison of races of bees, not a list of management procedures.
1. EGG LAYING RATE
2. EGG VIABILITY RATE
3. BROOD CYCLE TIME
4. BROOD NURTURING
5. FORAGING AGGRESSIVENESS
6. TIME OF FORAGING
7. DISEASE RESISTANCE
8. PEST RESISTANCE
9. DEFENSIVE BEHAVIOR
10. SWARMING TENDENCY
11. WINTER HARDINESS
12. LIFE SPAN
13. BODY SIZE
14. SENSE OF SMELL
15. HYGIENIC CLEANING BEHAVIOR
16. TIME OF BROOD DEVELOPMENT
18. HONEY ARRANGEMENT
19. POLLEN COLLECTION
20. TYPE OF HONEY COLLECTED
21. COMB BUILDING
22. CAPPING STRUCTURE
23. PROPOLIS COLLECTION
24. BRACE COMB CONSTRUCTION
25. ABDOMINAL COLOR
26. ANTENNAE STRUCTURE
Colony strength affects productivity because of the high level of correlation between hive strength and honey production. Egg laying rate, egg viability rate, brood care, brood development time, life span, and several other factors affect colony strength.
A prolific Italian queen can lay about 2,000 viable eggs per day during peak brood rearing. Rates of up to 5,000 eggs per day have been reported for African queens. After watching a colony build up from just a handful of bees in the winter to occupy seven or eight deep brood chambers in the spring, one begins to appreciate just how many eggs are being laid.
Egg viability is affected by inbreeding because of parthenogenesis and the concentration of genetic defects. Only 15 variants of the sex allele have been identified to date. Since a queen mates with 17 drones on the average, at least one or two of them will have identical sex alleles with the queen. When an egg has identical sex alleles, the result is a diploid drone egg that the bees normally destroy shortly after hatching. Genetic code defects cause otherwise normal eggs to be non-viable. This is especially detectable in drone eggs because they contain only one set of chromosomes. Genetic selection must control inbreeding so the egg viability rate does not become abnormally low.
Brood care includes feeding and climate control in the brood nest. Most strains of bees used commercially today show good brood care characteristics. Worker brood development takes 21 days from egg laying to adult. For comparison, African bees take about 19 days. The shorter brood cycle helps explain their rapid colony buildup.
The average worker lives about 35 days during summer. If the average life span were increased to 45 days, colony strength would rise by 20 to 30 percent. Several colonies have been found with above average life spans, but very little work has been done to select long-lived bees.
Disease resistance to brood diseases has been found for the following; American foulbrood, European foulbrood, Sacbrood, and Chalkbrood. There are several other brood diseases caused by viral, bacterial, and fungal agents, but none have as much effect as the first four. Resistance seems to center around hive cleanliness and brood nutrition with emphasis on hygienic behavior which is a tendency to uncap and remove diseased brood. Carniolans have a high average level of resistance to brood diseases and African bees show a similar capacity. Italians show resistance to varying degrees and respond readily to genetic selection.
Nosema, Paralysis, and Septicema are the primary diseases of adult bees. Nosema is especially bad because it affects wintering colonies causing serious damage in Canada and most of the northern United States. Factors affecting resistance include the total number of bees in the colony and the size of the hindgut of individual bees. Italians on average tend to be slightly susceptible to nosema and resistant to paralysis and septicema. Brother Adam indicates that he has found no obvious resistance to nosema except possibly in the Egyptian bee (Apis Mellifera lamarckii). Caucasians tend to be very susceptible to nosema though selected strains exhibit some resistance. Several researchers have noted that the eastern honeybee (Apis Cerana) seems to be almost immune to nosema. Regrettably, Apis Cerana and Apis Mellifera cannot crossbreed.
A moderate level of infestation with tracheal mites results in poor wintering ability. If more than about 30 percent of the workers are infested going into winter, the colony will probably die. Resistance appears to be based on behavioral and anatomical differences. Bees with the highest level of resistance currently are from England where bee populations were decimated in the early 1920's. As the highly susceptible bees were killed, only the resistant colonies survived. The net result is that bees of English origin have a high level of genetic tolerance to tracheal mites. The typical pattern seen when a colony dies from tracheal mites is a colony with a handful of dead bees and almost all the honey stored for wintering still in the hive. What happened to the huge cluster of bees that went into winter? They flew out and died when the temperature was above about 40 degrees. It is heartbreaking to see a huge cluster on the ground in front of a hive with bees crawling slowly away, wings disjointed. After losing most of the adult bees, the few remaining start rearing brood in a desperate attempt to survive. Then comes severe cold weather and the bees won't move from the brood to food located only inches away. The result is a handful of starved bees covering a small patch of brood with a hive still nearly full of honey.
Varroa mites are from Asia where colonies of Apis cerana were the original hosts. Varroa will kill an infested colony within a few years. Only African bees (Apis Mellifera Scutellata) show a high level of resistance. This resistance comes from a shorter brood development time and from actively seeking and killing the mites in a form of grooming behavior. Varroa causes newly emerged bees to be physically smaller than normal and to have short, abnormal wings. Other symptoms include excessive fall swarming, and brood that does not emerge from the cells.
Tropilaelaps Clarae is an external mite that also originated in Asia where they are hosted by Apis dorsata. Though not currently in the United States, we will probably have to deal with them eventually though only in the southern states. Resistance will probably be the same as for Varroa, though this has not yet been tested.
Wax moths can destroy the combs in a weak colony in a short time. Italians tend to be highly resistant because they maintain very strong colonies and aggressively clean the hive interior. They sting and remove wax moth larvae.
Parasitic insects such as hornets, wasps, and members of closely related genera such as spiders actively prey on honeybees by waiting near the hive entrance and grabbing a bee on its way in or out of the hive. Most colonies that aggressively guard and defend the hive will be resistant, but tend to sting beekeepers more often. African bees have developed a unique behavior of flying straight into the hive entrance instead of landing outside and walking in. This reduces their exposure to predators waiting at the entrance. While animals such as frogs, birds, skunks, and bears prey on honeybees, the only resistance bees show is based on strong hive defensive behavior. Guard bees and soldier bees tend to sting more than younger house bees. Guard bees normally stand near the hive entrance and challenge intruders. Soldier bees forage part of the time, then wait in the hive for the unwary intruder - whether man or beast. There is a large variation in the percentage of soldier bees in different colonies and there is some correlation between the percentage of soldier bees and the amount of honey produced. The more often a bee flies outside to forage, the more honey gathered. Regular bee selection has tended to increase the percentage and quantity of active foragers in commercially available strains of bees.
Foraging behavior shows up most in the amount of honey a colony gathers. In some colonies, the bees rush in with a load of nectar, unload, and then rush back out for another load. The bees in other colonies could best be described as lazy. They gather nectar, then return to the hive and lounge around for a while eventually getting around to another foraging trip. A good selection program can rapidly affect this level of genetic variation. African bees forage earlier in the morning, later in the evening, and more aggressively than European types.
Swarming is the natural means of reproduction for honeybees. Crowding is a primary cause of swarming and some colonies show more tolerance to crowding than others. Swarming is also influenced to a great degree by the climate and nectar flow characteristics. In general, areas having a long warm period in early spring with intermittent nectar flows and rainy periods that confine the bees to the hive will have the most intense swarming. By contrast, those areas having a long and cool buildup period and a sudden, intense nectar flow will experience swarming to a lesser degree. Regardless of location, swarming is one of the unique activities of bees that must be controlled to produce honey. According to Brother Adam, Greek bees (Apis Mellifera Cecropia) show the least inclination to swarm.
Winter hardiness is required in all areas of the United States and Canada but is of less importance in the southern United States. Carniolans show a good wintering ability as also does the intermissa race group. Brother Adam reports that Anatolian and cyprian bees show the best winter hardiness which is surprising because of their mediterranean origin. Italians have a less developed wintering ability which has prevented them from being imported into areas that experience extremes of cold in winter. Bees of the intermissa race group range up to the Arctic Circle which indicates that crossbreeding and selection with these hardy bees could dramatically improve wintering ability.
Body size and anatomical structure varies among different race groups. Currently, the largest bee is from the Rif Mountains of Morocco (Apis Mellifera major nova). Some of the African races tend to be the smallest. Tongue length, leg length, abdominal size, wing size, and virtually all anatomical features show some variation.
Tongue length and wing size have a significant effect on the honey crop. Antennae structure affects the sense of smell and touch and possibly other senses that we do not fully understand. This affects the bee's sense of orientation in finding the right hive, and affects foraging behavior because the bee can smell nectar at a greater distance. Drone antennae are much more sensitive than worker antennae. Most other anatomical features are of little importance because they do not significantly influence the honey crop.
The time of brood development is genetically determined with races such as carniolans having an abrupt spring buildup and caucasians having a long slow summer buildup. This is of importance because a strain that reaches peak development at the beginning of the major nectar flow gathers the most honey.
Thrift is the tendency to raise brood at the right time to gather honey and to slow down or stop brood rearing when there is no nectar flow. Most parts of the United States experience a major spring nectar flow followed later by a fall flow. This requires a corresponding spring peak of brood rearing and another peak in the fall. Italians show a tendency to such a development cycle but are unthrifty because they continue to raise large amounts of brood through the summer between flows. Bees adapt rapidly to an area when selection is used, or adapt more slowly when natural selection occurs. By one estimate, about 50 to 100 years of living and surviving in a given area results in an adapted strain. Maximum thrift is obtained when bees are genetically adapted to the local nectar flow conditions.
Honey arrangement and type of honey collected vary considerably with Italians tending to collect light colored honey and to store it above and out of the brood nest. In one instance, I had a colony of Italians beside a colony of german descent. The Italians gathered three shallow supers of beautiful golden honey while the germans gathered two supers of dark bad tasting honey. Carniolans also tend to collect lighter colored honey.
Some races of bees hoard pollen more aggressively. This is of importance where bees are used for pollination. The previously mentioned german bees collected and stored twice as much pollen as the Italians. They crowded the brood nest with pollen and stored pollen in every super of honey rendering it unfit for use as chunk comb honey. If pollination were of primary importance, then these bees would have been excellent. This trait can be selected for fairly rapidly by simply measuring the amount of pollen collected by a colony relative to the amount of brood in the colony and comparing with other similar colonies.
Comb and capping structure vary considerably. Size and length and cell angle from horizontal all vary by race and by strain. Cappings range in color from gray to white and in shape from flat to ridged to domed. Italian cappings are generally flat and white with raised ridges over the surface of the comb. Brother Adam's buckfast bees build white slightly dome shaped cells which improves the appearance of comb and chunk comb honey. White cappings are a result of an air gap between the cell cap and the honey in the cell. Dark cappings result when there is no air gap. Brood cappings and drone cell cappings for most races are dome shaped although there is considerable variation on this point. Some members of the intermissa race group add propolis to the wax used for cappings. This gives a dirty gray capping which ruins comb honey.
Calmness is the ability to stay fast on a comb during examination without nervous motion. Carniolans tend to be very calm with Italians less so. German black bees tend to be very nervous and jittery. I have opened hives that no amount of smoke would calm and I have opened others so calm that smoke was not even needed. Selection work for good temper shows conclusively that bees can be gentle and outstandingly productive. Note that the buckfast strain currently available in the United States is more aggressive than the strain Brother Adam was propagating 30 years ago. This appears to be the result of a greater focus on breeding for productivity and disease resistance.
Propolis collection and use varies considerably with Caucasians being heavy users and Egyptian bees using none. The average Italian or carniolan colony collects much more propolis than beekeepers would like. There is some conjecture that propolis collection may be connected to wintering ability. One of the greatest improvements we could make in bees today would be to reduce the amount of propolis collected. Unfortunately, very few selection programs have emphasized this much-needed trait.
Brace and bridge comb is built between combs and causes headaches for beekeepers because moveable combs become almost unmovable. This can be especially messy during spring inspection when brood combs have to be scraped and pried out of position. There is enough variation in this tendency that selection results in significant reduction in these structures. Brother Adam records that cyprian bees build very little bridge and brace comb.
Bee color varies from very light yellow to orange to brown to black. Bee hair color ranges from white to gray to yellow to black. Bees that are selected with color being a major emphasis invariably lose characteristics of greater importance such as honey gathering ability. A strain descended from Italians and known as golden Italians was developed several years ago but never achieved commercial importance because they didn't produce enough honey and didn't winter well. I have a much greater preference for productive bees than for pretty bees.
This list is by no means complete. According to one reference, the honeybee genome contains over 30,000 genes and each gene could have innumerable variations. Almost all the items I have listed are controlled by large numbers of genes. Bees adapt genetically to an area over a period of years based on survival of the fittest. The amount of genetic variation in honeybees shows that nature is a very harsh taskmaster. There is no absolute best bee, just a better adapted bee.