Assessment of soil suppressiveness : the system of fusarium foot rot on wheat

Abstract: The soil suppressiveness to fusarium foot rot caused by Fusarium graminearum and Fusarium culmorum was assessed by two complementary analyses: the bioassay and the fungistasis test. The bioassay addresses suppressiveness to fusarium foot rot and the fungistasis test evaluates the pathogen suppression capacity of different soil samples. A field experimental set up to study effects of conventional and reduced tillage and different preceding crops (wheat, oat and oilseed rape) was used for the study. In addition to establish the methodology for assessing the suppressiveness to fusarium foot rot caused by F. graminearum and F. culmorum, the different cultural practices were evaluated in their impact on the suppressiveness. Reduced tillage increased the suppressiveness to fusarium foot rot caused by F. graminearum, since reduced tillage decreased disease severity of the wheat plant growing on soil with wheat as preceding crop in the bioassay. In addition, reduced tillage decreased the germination rate of conidia spores of F. graminearum in the fungistasis test. For F. culmorum, no impact of the tillage treatment on the suppressiveness could be detected. Soil with oilseed rape as preceding crop showed the lowest disease incidence in the bioassay, what suggests that crop rotation with oilseed rape increases the suppressiveness to fusarium foot rot. Cultural practices which showed a significant effect on disease suppression, did not necessarily show an effect on pathogen suppression which was also influenced by the two Fusarium species differently due to their different ecology.