An Alternative, High Throughput Method to Identify Csd Alleles of the Honey Bee.

Éva Kolics,János Taller,Kinga Szepesi,Eszter Virág,Tamás Parrag,Balázs Kolics,Botond Heltai,Ferenc Házi,László Orbán,Kinga Mátyás,Barbara Kutasy

doi:10.3390/insects11080483

Abstract

Applying instrumental insemination in closely related honey bee colonies often leads to frequent lethality of offspring causing colony collapse. This is due to the peculiarities of honey bee reproductive biology, where the complementary sex determination (csd) gene drives sex determination within a haplodiploid system. Diploid drones containing homozygous genotypes are lethal. Tracking of csd alleles using molecular markers prevents this unwanted event in closed breeding programs. Our approach described here is based on high throughput sequencing (HTS) that provides more data than traditional molecular techniques and is capable of analysing sources containing multiple alleles, including diploid individuals as the bee queen. The approach combines HTS technique and clipping wings as a minimally invasive method to detect the complementary sex determiner (csd) alleles directly from honey bee queens. Furthermore, it might also be suitable for screening alleles of honey harvested from hives of a closed breeding facility. Data on alleles of the csd gene from different honey bee subspecies are provided. It might contribute to future databases that could potentially be used to track the origin of honey. With the help of tracking csd alleles, more focused crossings will be possible, which could in turn accelerate honey bee breeding programmes targeting increase tolerance against varroosis as well.

Highlights

More than fifty years before the discovery of sex chromosomes [1], it was reported that unfertilized eggs of the honey bee (Apis mellifera L., 1758) develop into haploid drones, whereas fertilized ones develop into diploid females [2]
We investigated the applicability of sex determination region genotypes of honey bee for rapid genetic assessment of hives through the testing of queen bees or honey by high throughput sequencing
This has obvious restrictions for queen breeding practice, since drones are present only during certain parts of the year. They may be even absent during the whole first year since young queens typically produce few or no drone brood. This is especially true for queens from breeding programmes, where swarming drive is one of the most important selection criteria

Summary

Introduction

More than fifty years before the discovery of sex chromosomes [1], it was reported that unfertilized eggs of the honey bee (Apis mellifera L., 1758) develop into haploid drones, whereas fertilized ones develop into diploid females [2]. The genetic basis of their sex determination (SD) appears to be diverse and poorly understood [4]. It was discovered in a wasp Bracon hebetor that diploid males hatched from fertilized eggs are highly unviable [5]. The same phenomenon was reported from the honey bee [6]. Based on these findings, it was suggested that the complementary sex determiner (csd) gene represents the primary signal that directs sexual development [7,8,9]. The product of csd is encoded by an autosomal locus within the SD cascade

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Results

Conclusion