The honey bee is indirectly responsible for one third of the worlds food supply through its pollination activity on more than 90 species of plants. (Greenleaf and Kremer. 2006).Since flowering plants and honey bees co-evolved together their survival depends on each other. However, the Varroa destructor mite and its effect on honey bee health threatens the honey bees existence. The exchange of honey bee colonies between Asia and Europe resulted in Varroa Destructor infecting Apis Mellifera in about 1960, and varroa mites were found in North American honey bees in 1987 (cf reviews Sanford, M. 2001). North American honey bees having no resistance died within 2 to 3 years after varroa infection. Chemical treatments with acaricides was initially effective at reducing varroa populations; however, the varroa mites soon developed resistance (Milani 1995, cf review Milani 2001.). In addition, chemical treatment of mites prevented selection pressure for the development of natural tolerance to parasitic mites and possibly makes honey bees even more susceptible to secondary infections (viruses, microsporidia, etc.) associated with mite infestations. Lack of genetic diversity in North American honey bee populations has also been a concern, since most commercial stock is produced by few queen breeders..
The Saskatraz project was initiated in 2004 with the intent of establishing a genetically diverse gene pool to breed for honey production, mite tolerance and resistance to brood diseases. Breeding for mite tolerance was approached by using natural selection, without using any synthetic chemical miticides. The first step was to gather together genetically diverse stock adapted to wintering in Saskatchewan, selected for honey production and brood diseases, such as chalk brood. Both tracheal (Acarapis woodi) and Varroa (Varroa destructor) mites arrived late into Saskatchewan, limiting exposure of local bees to these parasites. Most bee populations having limited exposure had no tolerance to varroa mites, but exposure to tracheal mites in some locations allowed some resistance to develop to the tracheal mite prior to initiation of the project. A request for breeding stock was responded to favourably by Saskatchewan queen breeders.
A collaborative initiative with the Ontario and Saskatchewan Beekeeper’s Associations resulted in the joint funding of the importation of Russian stock from the USDA research facility in Baton Rouge, La., USA. This stock was demonstrated to show some tolerance to varroa mites (Rinderer, et al 1997), in previous studies and a few Saskatchewan queen breeders had reselected stock imported between 2001 and 2004. In addition, stock (semen) from a German program (Buchler, etal 2002;2008) involved in selecting for varroa tolerance by natural selection was imported in 2004 and 2005.A number of other programs selecting for survival of colonies under varroa mite infestation without miticides treatment have been described (Rinderer etal. 2001; Leconte etal, 2007; Fries etal, 2007; Seeley etal, 2007).Other programs have focused on selecting for hygienic behaviour and suppression of mite reproduction, both traits which are correlated with varroa tolerance(Ibrahim and Spivak,2006;Harris.2007)
This report describes the results of selecting for both honey production and varroa tolerance with no synthetic chemical miticides, from a large, pre-selected, diverse gene pool over a period of three and a half years. In addition, close population mating by backcrossing selections at Saskatraz, with drone populations under high varroa mite infestations was performed. Methods are also described for enriching and maintaining the selected lines by outcrossing and recurrent selection. Microsatellite analyses is used to characterise genetic diversity and genotype specific breeding lines.
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