Role of Beneficial Bacteria in Disease Suppressive soils

Soil is of utmost importance for a variety of key functions that sustain life on earth, including nutrient cycling and plant growth. Soil microorganisms play an essential role in these processes and represent an enormous untapped resource for discovering novel traits and genes. In the past decades, specific soils have been identified worldwide in which beneficial microorganisms guard plants against infections by soilborne pathogens. This natural disease suppressiveness of soils is induced by successive cropping of susceptible host plants followed by a severe disease outbreak. To date, however, the molecular mechanisms underlying this ‘immune’ response of suppressive soils are largely unknown. Culture-based approaches used so far have led to the identification of only a few microbial species that contribute to natural disease suppression, but have not taken into account the vast majority and complex diversity of the indigenous soil microflora.

In two projects funded, one by NWO and one by the European Union, culture-independent approaches involving metagenomics and microarray-based community profiling are used to identify the key bacterial players, genes and mechanisms that are unique or highly enriched in disease suppressive soils. The identified bacteria and genes can be used to develop microbial indicators and molecular markers (biosensors) to monitor soil health and to determine the potential adverse effects of transgenic crop plants on soil ecosystems.