Soil suppressiveness to Rhizoctonia solani and microbial diversity.

Rhizoctonia solani anastomosis group 2-2IIIB causes damping-off, black root rot and crown rot in sugar beet (Beta vulgaris). Based on experiences of growers and field experiments, soils can become suppressive to R. solani. The fungus may be present in the soil, but the plant does not show symptoms. Understanding the mechanisms causing soil suppressiveness to R. solani is essential for the development of environmentally friendly control strategies of rhizoctonia root rot in sugar beet. A bioassay that discriminates soils in their level of disease suppressiveness was developed. Results of bioassays were in accordance with field observations. Preliminary results indicate an active role of microbial communities. Our research is focused on the disentanglement of biological mechanisms causing soil suppressiveness to R. solani in sugar beet. Therefore, we are handling a multidisciplinary approach through experimental fields, bioassays, several in vitro techniques and molecular techniques (PCR-DGGE).