Estimation of genetic parameters for honey production in the honeybee : preliminary results

The estimation of breeding values in genetic selection pro- grams is a tool of paramount importance, as it allows to iden- tify genetically superior individuals that can then become parents of the next generation, improving traits of economic interest. Honeybees represent an important productive live- stock species due to hive products such as honey, bees wax, pollen and to its invaluable role as pollinators of agricultural crops and wild plant species. Genetic evaluation in the honey- bee is considerably difficult due to their peculiar mode of reproduction. Phenotypes are measured on the colony, which consists of one queen and her daughters, i.e. thousands ofworkers. The queen is the only fertile female of the colony that mates with 10 to 20 drones just once, and stores a life lasting reserve of sperm cells in her spermatheca. Drones are haploid and their gametes are clones of their genotype. Furthermore, drones die right after mating, which means they mate just once in their lifetime. Restricted Maximum Likelihood (REML) and Best Linear Unbiased Prediction (BLUP) are important methodologies in livestock breeding for estimating variance components and predicting breeding values, respectively. These methods require information on the genetic relationship among tested individuals in order to estimate the individual additive gen- etic merit for a phenotypic trait. Ordinary rules for the esti- mation of genetic relationship are not applicable to honeybees due to queen’s multiple mating and haploid males. The aim of the work was to develop a numerator relationship matrix adapted to honeybee peculiarities, in order to estimate breeding value, variance components and genetic parameters for honey yield. Tested colonies (n 1⁄4 120) derived from 8 paren- tal lines have been distributed in 4 apiaries nearby Lodi (Lombardy). Honey was harvested twice during spring 2016. A modified R function was used to compute the inverse of numer- ator relationship matrix, which is required for the estimation of variance components and the prediction of breeding values. The fitted mixed model included fixed effects of apiary, strength of the colony and production, and both genetic additive and per- manent environment random effects. Preliminary results show heritability and repeatability of honey production of 0.33 and 0.54, respectively. These results are in agreement with parame- ters estimated through different methods reported in literature.