Fungal plant pathogens and soil biodiversity

The role of biodiversity as it affects the control of soil-borne fungal pathogens is discussed. Soil-home fungal plant pathogens have often proven difficult to manage with conventional methods of disease control. Nonetheless, researchers have characterized several naturally occurring "disease-suppressive" soils where crop loss from disease is less than would otherwise be expected. Suppressive soils can also result from the incorporation of various amendments into soil. In most cases, disease control in such soils has been shown to be biological in nature; that is, soil organisms appear to directly or indirectly inhibit the development of disease. Increased knowledge of the identity and functioning of these organisms may support the development of techniques that can be used to develop suppressiveness in soils that are otherwise disease-conducive. Populations of pathogens themselves have been shown to exhibit considerable genetic diversity; the ability of populations to respond to disease control measures should be considered when developing a management strategy. New molecular techniques can be exploited to better characterize soil communities, including the pathogens themselves, as well as community responses to various disease control options. The contributions of Canadian researchers to these areas are discussed and models for further study are proposed.