|De Guzman, Lilia|
|Le Conte, Yves|
Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2009
Publication Date: 2/1/2010
Citation: Navajas, M., Anderson, D.L., De Guzman, L.I., Huang, Z.Y., Clement, J., Zhou, T., Le Conte, Y. 2010. New Asian Types of Varroa Destructor: A Potential New Threat for World Apiculture. Apidologie. 41(1):181-193. Interpretive Summary: Varroa mite is the most serious problem for Apis mellifera beekeeping worldwide. Molecular genetic monitoring may determine the comparative virulence of different genotypes of varroa on infested colonies. In this study, we identified a total of 18 mitochondrial haplotypes of varroa in Asia. Seven of these haplotypes were found infesting A. mellifera colonies. Infestations of two new variants of the K haplotype and two of the J haplotype were also detected on A. mellifera colonies. These new haplotypes may represent a potential threat to Western honeybees worldwide.
Technical Abstract: The invasion of the Western honeybee (Apis mellifera) by the Varroa mite (Varroa destructor) is attributed to two haplotypes (K and J) that shifted last century from their primary Eastern honeybee host (A. cerana) in north-east Asia. Molecular evidence indicates that both haplotypes are two partially isolated clones on Western honeybees, presumably because of events that occurred at the times of the host shifts. Here, mitochondrial DNA sequences spanning four different genes (COI, COIII, ATP6 and Cytb: 2,700 base pairs in total) were obtained from Varroa mites infesting both Eastern and Western honeybees (respectively 21 and 11 colonies examined) from Asia including regions where the shifts first occurred to, as a means of gaining further insights into the invasion biology of the mites. A total of eighteen mitochondrial haplotypes, each derived from one of four distinct haplogroups of V. destructor, were uncovered in Asia. From these, 11 haplotypes were found on A. cerana and seven on A. mellifera, with each population confined to a regional population of this bee species. Two new variants of the K haplotype and two of the J haplotype were found on Western honeybees in what appeared to be well-established infestations. These new types may represent a potential threat to Western honeybees worldwide. The extreme lack of polymorphism in the K and J haplotypes on Western honeybees outside of Asia, which has been described in previous studies, can now be plausibly explained as being due to genetic ‘bottlenecks’ that occurred in Asia before and after mites shifted from their original Eastern honeybee hosts.