1a. Objectives (from AD-416)
Objective 1: Identify and evaluate traits, genes, and markers associated with honey bee resistance to mites and pathogens, possibly including agents discovered to cause colony collapse disorder (CCD). Objective 2: Use traditional breeding and marker-assisted selection (MAS) to develop commercially desired honey bees (other than Russian bees, which are addressed in a sister project) with resistance to parasites (e.g., mites), depredators (e.g., small hive beetle), and diseases (e.g., fungi causing chalkbrood disease), possibly including agents discovered to cause CCD. Objective 3: Develop resistance-based integrated pest management (IPM) systems for management of pests in commercially desired honey bees (other than Russian bees), particularly systems useful for early spring build up.
1b. Approach (from AD-416)
Traits that are known to confer resistance to mites (autogrooming against tracheal mites; Varroa sensitive hygiene (VSH) or its behavioral subtasks against varroa) will be subjected to microarray analysis to identify genes associated with specific phenotypes. Genes will be further screened for up- and down-regulation using real time Polymerase chain reaction (rtPCR) assays. New traits of resistance to varroa (reduced invasion by mites into brood cells; brood-mediated suppression of mite reproduction) or to CCD-related agents will be sought by measuring variation among diverse bee sources. Traditional breeding will be used to create honey bees suitable for commercial crop pollination by combining lines having high VSH with commercial stock. Molecular-marker-assisted selection will focus on genetic markers developed earlier for autogrooming and VSH. Simplified methods for queen breeders to select for VSH will be evaluated by correlating VSH expression with changes in brood nest characters during short-term exposure of infested combs. Sustainability of varroa resistance in bees used for migratory crop pollination will be determined by measuring survivability and performance of VSH colonies in cooperation with commercial beekeepers. Recommendations for resistance-based Integrated Pest Management (IPM) systems against varroa will be developed by integrating resistant bee stock with other non-chemical means to manage varroa.
3. Progress Report
Information about the basic biology of the Varroa Sensitive Hygiene (VSH) trait is being sought to better understand how the trait regulates resistance to varroa mites. Current work is focusing on the chemical cues which elicit hygienic responses against mites. This work entails analyses of mixtures of chemicals collected from mite-infested brood, neurological responses of worker bees to specific chemicals from the mixture, and behavioral responses of workers to chemicals that are applied to capped brood. Colonies derived from a variety of commercial sources of VSH queens were evaluated for their hygienic responses to varroa mites. The mite resistance of these outcross VSH colonies was improved over that of unselected commercial colonies, and allows beekeepers to reduce or eliminate chemical treatments against varroa mites. The results also suggest that mite resistance could be improved further if more VSH drones sources were supplied by the commercial queen producers. Such information about end-use queens should improve the transfer of VSH-based resistance technology. The large commercial queen production industry on the Big Island of Hawaii is newly threatened by varroa mites. A breeding program was initiated in FY 10 to introgress VSH into existing stocks on a trial basis. In FY 11, three participating queen breeders established colonies having varying levels of VSH to assess how colonies perform in tropical beekeeping conditions. The addition of VSH suppressed population growth of varroa mites, but colonies with high levels of VSH tended to have smaller amounts of brood than colonies with lower levels. The results are helping guide two large queen producers who are continuing their breeding efforts with VSH. Formal technology transfer activities include an ongoing Cooperative Research and Development Agreement (CRADA) and new Material Transfer Agreements (MTA)s to deliver VSH germplasm to a variety of queen breeders. We also instructed queen breeders individually and at a national workshop on how to search for VSH in their own bees to help preserve genetic diversity.
Danka, R.G., Harris, J.W., Villa, J.D. 2011. Expression of varroa sensitive hygiene (VSH) in commercial VSH honey bees (Hymenoptera: Apidae). Journal of Economic Entomology. 104(3):745-749.