Genotype, but Not Climate, Affects the Resistance of Honey Bees (Apis mellifera) to Viral Infections and to the Mite Varroa destructor

Simple Summary The mite Varroa destructor, the viruses that it transmits, and the fungus Nosema ceranae, are among the main drivers of honey bee (Apis mellifera) colony losses. Honey bees are the main pollinators of flowering plants and contribute to one-third of food produced. Therefore, it is important to find out if there are honey bee strains that defend themselves better against these agents of disease. This study was conducted to determine if Africanized honey bees are more resistant than European honey bees to parasitic and viral diseases, as well as if their resistance is affected by climate. Consequently, the presence and levels of parasites and viruses was determined in 365 honey bee colonies of European or African ancestry in subtropical and temperate regions of Mexico. Varroa and Nosema were the most and least frequently found parasites (95% and 15%, respectively). Deformed wing virus (DWV) and black queen cell virus (BQCV) were the only viruses detected at frequencies of 38% and 66%, respectively. Varroa, DWV, and BQCV, were found at higher levels in colonies of European ancestry than in colonies of African ancestry. However, there were no effects of climate. Therefore, it is concluded that bee strain, but not climate, influences the resistance of honey bees to DWV, BQCV, and Varroa. This study was conducted to analyze the effect of genotype and climate on the resistance of honey bee (Apis mellifera) colonies to parasitic and viral diseases. The prevalence and intensity of parasitism by Varroa destructor, or infection by Nosema spp., and four honey bee viruses were determined in 365 colonies of predominantly European or African ancestry (descendants of A. m. scutellata) in subtropical and temperate regions of Mexico. Varroa destructor was the most prevalent parasite (95%), whilst N. ceranae was the least prevalent parasite (15%). Deformed wing virus (DWV) and black queen cell virus (BQCV) were the only viruses detected, at frequencies of 38% and 66%, respectively. Varroa destructor was significantly more prevalent in colonies of European ancestry (p < 0.05), and the intensity of parasitism by V. destructor or infection by DWV and BQCV was also significantly higher in colonies of European descent than in African descent colonies (p < 0.01), although no genotype-parasite associations were found for N. ceranae. Additionally, significant and positive correlations were found between V. destructor and DWV levels, and the abundance of these pathogens was negatively correlated with the African ancestry of colonies (p < 0.01). However, there were no significant effects of environment on parasitism or infection intensity for the colonies of both genotypes. Therefore, it is concluded that the genotype of honey bee colonies, but not climate, influences their resistance to DWV, BQCV, and V. destructor.