Honeybee (Apis mellifera L.) resistance to the Microsporidium Nosema ceranae in Plantations of Eucalyptus grandis

Doctoral thesis abstract

Abstract

Nosemosis of honey bees (Apis mellifera) is a disease of adult bees, primarily causing disorders in the digestive tract. In Uruguay, Nosemosis occurs in the colonies which are moved to plantations of Eucalyptus grandis. The hypothesis of the present thesis, states that nosemosis by N. ceranae causes severe damage to honey bee colonies located in plantations of E. grandis. However, the magnitude of this damage and the subsequent restoration of colony health, depend on the environment conditions. On the other hand, there are colonies with differential genetic resistance to infection by N. ceranae, and this resistance could be related to a better immune response. To corroborate these hypotheses, five works were carried out. In the first two, it was demonstrated that N. ceranae differentially affected the honey bee colonies depending on the environment in which they were. In the third study, we found that africanized bees were less infected with N. ceranae and with Black queen cell virus (BQCV), and produced more honey than European bees. In the next study, we attempted to increase the resistance and susceptibility of the colonies against N. ceranae, through a bidirectional selection that did not handled the paternity of the workers. Firstly, colonies with differential resistance against the microsporidium were identified, in the first generation resistant colonies had fewer spores per bee than susceptible colonies, but these results were not sustained in the next generation, suggesting the need to improve the selection methodology. Finally, we assessed whether the differential resistance against N. ceranae would be linked to a better immune response, obtaining negative results.