Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 8/31/2009
Publication Date: 9/10/2009
Citation: Mazzola, M. 2009. Active manipulation of native soil microbial community structure and function to suppress soilborne diseases. Meeting Abstract. P. 1-11. Interpretive Summary: Soil ecosystems possess a wealth of biological resources that can be harnessed for use in control of plant diseases. Soils that naturally have low incidence of disease are commonly referred to as suppressive soils. Studies have been conducted to determine the properties of these soils that are important in this natural disease suppression, the goal being to identify those soil components that function to limit plant disease. Once the important disease-limiting components are identified, the hope would be to transfer these elements to other soils as a means to induce natural biological disease control. These studies demonstrated that growing wheat in orchard soils prior to planting apple, significantly depressed root infection by the fungal pathogen Rhizoctonia solani. It was shown that wheat suppressed this pathogen by enhancing populations of certain bacteria that are able to inhibit growth of R. solani. However, not all wheat varieties were able to reduce root infection by R. solani. It was shown that wheat cultivars that were best at providing disease control were the same cultivars that supported the highest populations of the bacterium Pseudomonas putida btp A. Specific soil amendments also possess the ability to transform resident microbial communities in a manner which induces natural soil suppressiveness. These include various plant residues and waste products that are naturally available in farming systems. The formulation of strategies to effectively utilize these processes will have a significant role in environmentally sustainable systems for management of soilborne plant pathogens.
Technical Abstract: The reality of naturally occurring biologically-induced disease suppressive soils suggests opportunity for managing resident soil microbial communities as a disease control method. Disease suppressive soils have yielded a significant body of knowledge concerning operative mechanisms leading to the suppressive state, and have been a primary source of microbial strains utilized for the biological control of soilborne diseases. However, significant difficulty has been realized in the transfer of this knowledge and these resources into the development of effective field-level disease control practices. Efforts have primarily focused on the commercial development of biological control agents, and subsequent inundative application of individual or mixtures of microbial strains recovered from these systems. However, the introduction of biological agents into non-native soil ecosystems commonly fails to yield commercially viable or consistent levels of disease control in soilborne systems. Of late, greater emphasis has been placed on manipulation of the cropping system to manage resident microbial community structure and function as a means to suppress soilborne plant pathogens. Numerous strategies for the management of this biological resource have been proposed, but few have been evaluated in field production systems. Tactics that has been evaluated include the cropping of specific plant species or genotypes, cultivation of green manures or the application of soil amendments with the goal of selectively enhancing disease suppressive microbial communities. The viability and limits of such approaches for the management of soilborne diseases in commercial agricultural production systems is discussed.