Crop rotation effects on incidence and diversity of Fusarium species colonizing stem bases and grains of winter wheat

Fusarium head blight (FHB) and Fusarium crown and foot rot (FCR) are the most important diseases caused by Fusarium species in wheat. Although the range of Fusarium species colonizing wheat ears and stem bases is known, the impact of various crop rotations on the diversity and incidence of such species has not been investigated thoroughly. We therefore analyzed the occurrence of Fusarium species on stem bases and grains of wheat grown in four different long-term crop rotations that included winter wheat, maize, sugar beet and oil radish as pre-crops. The results demonstrate that, regardless of the crop rotation, the range of Fusarium species that colonized stem bases and grains of wheat was consistent. Stem bases were predominantly infected by F. culmorum, F. equiseti and F. tricinctum, while F. graminearum, F. poae and F. tricinctum were mainly found on grains. However, the colonization frequencies of Fusarium spp. both in stem bases and grains were differentially affected by crop rotations. Highest infestation in grains was found when wheat was grown after maize, dominated by F. graminearum, while wheat grown after sugar beet led to highest colonization frequencies of F. culmorum in stem bases. Among all identified Fusarium species, F. culmorum was the dominant causal agent of FCR. The results of this study indicate that sugar beet and maize as pre-crops of wheat may increase the risk of FCR and FHB, respectively, to a much greater extent than wheat grown after wheat, which did not have such critical effects on the incidence of the two diseases.