This thesis investigates the effects of genetic modification of the starch quality in potato on the structure and function of the soil fungal community via changes in root-exudates and litter composition, and compares the observed differences between the GM- and its parental variety in the context of the __normal__ variation effected by conventionally produced cultivars. In order to study the fungal community composition and functionality, an integrated approach of molecular fingerprinting methods and measurements of fungal enzymes involved in degradation of organic matter in the soil was employed. In field experiments the effect of soil type, season and plant growth stage on rhizosphere fungi were evaluated and in the greenhouse experiments stable isotopes were employed to monitor carbon flow from the plant to rhizosphere microbes and a decomposer experiment was designed to investigate the faith of the potatoes and leaves possibly left into the soil. The detailed greenhouse studies revealed differences between GM- and its parental variety. The field studies, however, confirmed that these differences are transient in field conditions and that fungi in the potato rhizosphere are affected more by soil type, sampling year, plant growth stage and cultivar type than the genetic modification.LEI Universiteit LeidenPlantenecologi
