Fungal plant pathogens and soil biodiversity

Abstract

The role of biodiversity as it affects the control of soil-borne fungal pathogens is discussed. Soil-borne 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. Key words: Biocontrol, molecular technologies, functional diversity, integrated pest management

Negative feedback on a perennial crop: Fusarium crown and root rot of asparagus is related to changes in soil microbial community structure

“…We observed a 30% reduction in microbial biodiversity early in the Fusarium-related field depopulation process, followed by a recovery in the level of biodiversity correlated with further increase in field area affected by FCRR. This observation underscores that biodiversity in itself might not be a sufficient condition for a soil to be disease-suppressive and concurs with others on the importance of the composition of the soil microbial community (Reeleder, 2003).…”

Biotic interactions, ecological knowledge and agriculture

“…General disease suppression is thought to be caused by increased competition for nutrients, especially soil carbon, when microbial activity is increased (Reeleder 2003). In a comparison of organic and conventional farms, suppression of corky root on tomato was greater in the organic than the conventional fields.…”

Genetic and pathogenic diversity of Neofusicoccum parvum in New Zealand vineyards

“…The genetic diversity of a fungal population is an important feature that can provide information about dispersal and distribution of particular genotypes in different localities (Reeleder 2003). It is influenced by the relative contribution of the asexual and sexual reproduction of a species, with a sexually reproducing species usually having a more genetically diverse population than an asexually reproducing species (Cortesi & Milgroom 2001).…”