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Inbred Until Dead
Beekeepers and queen breeders have been selecting queens for favorable traits for many years. Breeding and selecting within a closed population is known as line-breeding. Some managed sub-species maintain a single subspecies, i.e. Russian, some are hybridized, i.e. Midnight. There have been attempts to inbreed queens for specific traits. The challenge with exclusive sub-species and inbred species is maintaining genetic purity usually through artificial insemination. The vitality of homozygous, inbred, sub-species decreases with generations.
Living creatures pass their inheritance in genes. Gene variations are called alleles. Reproducing species inherit one set of alleles from each parent for two sets of alleles. Alleles can be dominant, recessive or co-dominant. Cells that carry genes have cellular bodies identified as chromosomes. Honey bees have 32 chromosomes. The egg and sperm each have half the chromosomes or are haploid. Drones have a haploid of 16 because they are unmated.
Crossing of unrelated sub-species results in hybrid vigor. The offspring exceed the vitality of either parent. This unexplained increase in life force is known as heterosis. Many more genes with more allele pairs are possible with the hybrid. The progeny or offspring is heterozygous. An increase in heterozygosity results in heterosis.
Inbreeding increases homozygosity and reduces heterosis. Increased homozygosity causes inbreeding depression. The offspring lose vigor, experience slow colony build-up, lose disease resistance, experience decreased production and higher winter loss. Sound a little like CCD or the recent increase in viruses detected?
The main problems of line-breeding are poor brood pattern, loss of vigor, and rapid fixation of characteristics for good qualities with diminishing returns. That is the challenge faced by any breeder with a closed population. The United States basically has a closed population since 1922. There has been a very limited importation with extensive quarantine. Queen breeders are very familiar with the vigor of fertilized offspring after extended storage of the sperm. The airlines always take great care with everything shipped so we know everything imported since 1922 is outstanding quality.
The Honey Bee act of 1922 was implemented to stop the spread of diseases. Well the diseases are already here and the bees that have developed resistance are not allowed in to help America. There are actually two methods to re-introduce resistance – line-breeding for positive qualities –or- homogenize several sub-species with desired qualities. Australia and New Zealand have chosen the heterogenic population.
In nature a queen mates in flight with up to 20 males with various alleles. In America she has still mated in the closed pool. If sperm from several continental regions is homogenized, the gene pool just went global expanding the closed population. Drone semen from numerous sub-species is stirred together. Artificial insemination with sperm homogenized from 20 or more drones creates a diverse population within the hive. Only nine of 26 sub-species are in the United States. Workers resistant to disease flourish more than their weaker sisters. Vigorous foragers produce greater yields. Pollinators with greater vitality get more contracts and are bred in preference by the beekeepers.
USDA allowed limited Carniolan imports in 1993. Varroa parasitized the Eastern Russia coastal region on the Primorski Peninsula. Adam (Karl Kehrle) searched Europe and Africa to develop a 'mutt" bee resistant to tracheal mites that decimated Europe and led to the ban of 1922. 1980 Weaver Apiaries of Navasota, Texas started importing Buckfast semen. The offspring of this haploid genetic infusion are a different color but more importantly not as idealistic as the original. We live in a global society, with global trade, global travel, and disappearing borders. The diseases, pests and parasites cross the border, but resistant bees are stopped at the gate.
These are actual results of heterotic bee breeding reported in Heterosis in the Honey Bee (Apis Mellifera L.), Gladstone H. Cale, Jr. and John W. Gowen’, Dadant & Sons, Inc., Hamilton, Illinois and Genetics Department, Iowa State College, Ames, Iowa Received October 10, 1955
“Heterotic effects were demonstrated for both oviposition rate and honey yield. These effects were such that five of the six hybrid queen groups exceeded their higher parent in oviposition rate, and four of the groups headed by hybrid queens exceeded their higher parent for honey yield. Expressed as a percentage of the higher parent, the egg productivities of the hybrid queens ranged from 128 percent to 166 percent, with an average productivity increase of 35.5 percent. Hybrid queen honey yields ranged from 100 percent to 129 percent of the higher parent, with an average yield over the higher inbred parent of 15 percent. The oviposition rate of the average hybrid queen was 107.2 percent that of queens selected at random from the stock distributed throughout the United States. The two better hybrids exhibited productivities of 114.4 and 116.7 percent of the random stock.”
Heterosis in the Honey Bee (Apis mellifera L.)
Gladstone H. Cale, Jr. and John W. Gowen’
Improving Our Bee Stocks: Why it is so difficult to do, Mr. D.W.J. Yanke Daykel Apiaries
CALE, G. H. JR, 1952 Oviposition rates and viability of eggs in Apis mel@fera L. Unpublished M.S.
Thesis. Ames, Iowa, Iowa State College Library.
GOWENJ,. W., 1952 Hybrid vigor in Drosophila. Heterosis. Edited by J. W. Gowen. Ames, Iowa,
Iowa State College Press.
GOWENJ, . W., and L. E. JOHNSON, 1946 Metabolic capacity of different races of Drosophila melanogaster
for egg production. Am. Naturalist 80: 149-179.
GOWENJ,. W., J. STADLEBan, d L. E. JOHNSON, 1946 On the mechanism of heterosis-the chromosomal
or cytoplasmic basis for heterosis in Drosophiia melanogaster. Am. Naturalist 80: 506-
LOH, S. Y., 1949 Early testing as a means of evaluating FI heterosis between inbred lines of Drosophila
melanogaster. Unpublished Ph.D. Thesis. Ames, Iowa, Iowa State College Library.
MACKENSE0N., W., 1951 Viability and sex determination in the honey bee (Apis melZ+;rera L.).
Genetics 36: 500-509.
NOLANW, . J., 1923 Two year brood curve for a single colony of bees. J. Econ. Entomol. 16: 117-124.
ROJAS, B. A., 1951 Analysis of a group of experiments on combining ability in corn. Unpublished
M.S. Thesis. Ames, Iowa, Iowa State College Library.
SPRAGUEG,. F., and L. A. TATUM19,4 2 General and specific combining ability in single crosses of
corn. J. Am. Soc. Agron. 34: 923-932.
STRAUSF, . S., 1942 Genetic mechanisms of heterosis. Unpublished Ph.D. Thesis. Ames, Iowa,
Iowa State College Library.
TABERS,. , 1954 The frequency of multiple mating of queen honey bees. J. Econ. Entomol. 47:995-998.