Honey bee predisposition of resistance to ubiquitous mite infestations

Abstract

Host-parasite co-evolution history is lacking when parasites switch to novel hosts. This was the case for Western honey bees ( Apis mellifera ) when the ectoparasitic mite, Varroa destructor , switched hosts from Eastern honey bees ( Apis cerana ). This mite has since become the most severe biological threat to A. mellifera worldwide. However, some A. mellifera populations are known to survive infestations, largely by suppressing mite population growth. One known mechanism is suppressed mite reproduction (SMR), but the underlying genetics are poorly understood. Here, we take advantage of haploid drones, originating from one queen from the Netherlands that developed Varroa -resistance, whole exome sequencing and elastic-net regression to identify genetic variants associated with SMR in resistant honeybees. An eight variants model predicted 88% of the phenotypes correctly and identified six risk and two protective variants. Reproducing and non-reproducing mites could not be distinguished using DNA microsatellites, which is in agreement with the hypothesis that it is not the parasite but the host that adapted itself. Our results suggest that the brood pheromone-dependent mite oogenesis is disrupted in resistant hosts. The identified genetic markers have a considerable potential to contribute to a sustainable global apiculture.

Factors restraining the population growth of Varroa destructor in Ethiopian honey bees (Apis mellifera simensis)

“…Thus, when no adult male mites are found in the dark grey headed stage, it means that the male development is at least strongly delayed. Although several studies demonstrate that honey bees left untreated in Europe also develop suppressed mite reproduction [39, 41], the inability to produce adult male offspring has so far not been discovered outside Africa (except Africanized bees in Costa Rica; [81]).…”

“…In this ‘suppressed mite reproduction’ (SMR) trait the Varroa mite fails to produce offspring, which has an important impact on the mite population dynamics [40]. The underlying mechanism is not entirely clear, but the trait is exclusively expressed by the late larval or pupal stage [35, 41] as the mite reproduction takes place in the sealed brood cell. Moreover, it seems to occur both in worker and drone brood [35, 41] and has been reported in bees left untreated in Europe and in Apis mellifera scutellata in Africa [28, 29, 39–41].…”

“…The underlying mechanism is not entirely clear, but the trait is exclusively expressed by the late larval or pupal stage [35, 41] as the mite reproduction takes place in the sealed brood cell. Moreover, it seems to occur both in worker and drone brood [35, 41] and has been reported in bees left untreated in Europe and in Apis mellifera scutellata in Africa [28, 29, 39–41]. Our research group has recently unlocked the genetic predisposition of the SMR trait of honey bees of the Amsterdam Water Dunes (The Netherlands) by combining whole exome sequencing and elastic-net regression [41].…”

“…Moreover, it seems to occur both in worker and drone brood [35, 41] and has been reported in bees left untreated in Europe and in Apis mellifera scutellata in Africa [28, 29, 39–41]. Our research group has recently unlocked the genetic predisposition of the SMR trait of honey bees of the Amsterdam Water Dunes (The Netherlands) by combining whole exome sequencing and elastic-net regression [41]. A molecular mechanism has been proposed in which the chemical communication between the honey bee larva and the Varroa mite is disturbed, and as a consequence hereof the onset of mite oogenesis failed.…”

Three Decades of Selecting Honey Bees that Survive Infestations by the Parasitic Mite <em>Varroa destructor</em>: Outcomes, Limitations and Strategy

“…This widespread monitoring may help to identify numerous loci with a direct impact on the resistance of colonies of western honey bee against the Varroa mite. Many loci linked to diverse resistance traits have already been identified (Arechavaleta-Velasco et al, 2012;Behrens et al, 2011;Broeckx et al, 2019;Guarna et al, 2017;Hamiduzzaman et al, 2017;Harpur et al, 2019;Hu et al, 2016;Jiang et al, 2016;Lapidge et al, 2002;Morfin et al, 2019a;Oxley et al, 2010;Spötter et al, 2016;Spötter et al, 2012;Tsuruda et al, 2012;Zakar et al, 2014). Even though each of these studies mentions the possibility of using marker-assisted or genomic selection in honey bee breeding, to the best of our knowledge, the identified sequences have not been routinely implemented in selection programmes.…”