Two quantitative trait loci are associated with recapping of Varroa destructor‐infested brood cells in Apis mellifera mellifera

Abstract

Recapping of Varroa destructor-infested brood cells is a trait that has recently attracted interest in honey bee breeding to select mite-resistant Apis mellifera colonies. To investigate the genetic architecture of this trait, we evaluated a sample of A. mellifera mellifera colonies (N = 155) from Switzerland and France and performed a genome-wide association study, using a pool of 500 workers per colony for next-generation sequencing. The results revealed that two QTL were significantly (P < 0.05) associated with recapping of V. destructor-infested brood cells. The best-associated QTL is located on chromosome 5 in a region previously found to be associated with grooming behaviour, a resistance trait against V. destructor, in A. mellifera and Apis cerana. The second best-associated QTL is located on chromosome 4 in an intron of the Dscam gene, which is involved in neuronal wiring. Previous research demonstrated that genes involved in neuronal wiring are associated with recapping and varroa sensitive hygiene. Therefore, our study confirms the role of a gene region on chromosome 5 in social immunity and simultaneously provides novel insights into genetic interactions between common mite resistance traits in honey bees.

Evaluating the Potential of Brood Recapping to Select Varroa destructor (Acari: Varroidae) Resistant Honey Bees (Hymenoptera: Apidae)

“…A previous attempt to propose an easier method to evaluate recapping ended with unconvincing results, such as low heritabilities and low correlations with mite infestation ( Guichard et al 2021 ). The development of genome-based methods, however, appears promising to gain knowledge on the genetic background of recapping and to enable the emergence of genomic marker-assisted selection ( Brascamp et al 2018 , Bernstein et al 2021 , Guichard et al 2022 ), which might help increase the speed of genetic progress. Our results confirm the difficulty of identifying suitable traits for successful resistance selection programs but suggest that recapping is one of the promising candidate traits that may lead to colonies with an elevated resistance against Varroa destructor , or at least a significant reduction in the need for miticide treatments.…”

The mechanisms and factors that induce trained immunity in arthropods and mollusks

“…Many immune gene families of these PRRs in invertebrates could mediate the nonspecific immune response (17, 60, 61), which could also be a form of trained immunity whereby gene expression to synthesize immune proteins is induced by environmental changes. For example, the Down syndrome cell adhesion molecule (Dscam), which is well studied in invertebrates, has been shown to play a role in mounting adaptive-like immunity by specific splicing to produce different immune protein isoforms during pathogens stimulation (62)(63)(64)(65)(66). Similarly, C-type lectin-like domain (CTLD) proteins, which perform important tasks in immunity by acting as PRRs (67) and as effector proteins with bactericidal activity (68, 69), are expressed in the genomes of many organisms, including, cephalochordata, echinodermata, insecta, nematoda, cnidaria, porifera, and placozoa (70)(71)(72)(73)(74)(75)(76).…”

Sequence-based genome-wide association studies reveal the polygenic architecture ofVarroa destructorresistance in Western honey beesApis mellifera

“…However, tools to perform genetic association studies are so far not tailored to encompass such genetic characteristics, which limits the power of genomic studies performed on honey bees and their transferability into breeding tools. Some markers of interest have been identified (see Mondet, Parejo, et al 2020 for a review) but most genomic studies performed on honey bee traits so far were built on a limited number of samples (10 to 200 hundred individuals or colonies (Shorter et al 2012;Liu et al 2016;Southey et al 2016;Conlon et al 2019;Avalos et al 2020;Guichard, Dainat, Eynard, Vignal, Servin, Beestrong, et al 2021;Guichard, Droz, et al 2021;Guichard, Dainat, Eynard, Vignal, Servin, and Neuditschko 2022)), restricting the power of the analyses to come out as a general breeding tool. To date, the use of such markers has been limited, mostly due to a lack of easily accessible genotyping tools, leaving beekeepers with very limited access to varroa resistant stock.…”