Submitted to: Proceedings of Management of Soilborne Plant Pathogens
Publication Type: Proceedings
Publication Acceptance Date: 9/17/2002
Publication Date: 12/1/2002
Citation: MAZZOLA, M. DETERMINATIVE ROLE OF PLANT GENOTYPE IN COMPOSITION OF SOIL MICROBIAL COMMUNITIES AND INDUCTION OF SOIL SUPPRESSIVENESS. PROCEEDINGS, THIRTEENTH ANNUAL MEETING ON SOILBORNE PLANT DISEASES. AGRICULTURAL RESEARCH COUNCIL, PLANT PROTECTION RESEARCH INSTITUTE, STELLENBOSCH, SOUTH AFRICA. 2002. v. 13. p. 69-78. 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 goal would be to transfer these elements to other soils as a means to induce natural biological disease control. Studies conducted in this and other laboratories have demonstated that specific cropping sequences can induce development of a disease suppressive soil. Likewise, it was shown that in certain instances induction of a disease supressive soil occurs in a plant genotype-dependent manner. In this laboratory we have demonstrated that wheat cropping can induce suppressiveness to Rhizoctonia solani, but that the phenomenon is only generated by specific wheat cultivars. It was shown that wheat cultivars that were best at providing disease control were cultivars that supported the highest populations of certain genotypes of the bacterium Pseudomonas putida btp A. The ability to transform resident microbial communities in a manner which induces natural soil suppressiveness will have a significant role in environmentally sustainable systems for management of soilborne plant pathogens.
Technical Abstract: Suppressive soils are characterized by the absence of disease development even though a virulent pathogen and susceptible host are present. Biotic and abiotic elements of the soil environment contribute to suppressiveness, however most defined systems have identified biological elements as primary factors in disease suppression. Managing soil suppressiveness has been suggested as a plausible strategy to employ for the control of soilborne diseases. Results from this study demonstrated that the cultivation of orchard soils with wheat prior to planting apple could induce suppressiveness to Rhizoctonia root rot of apple. However, the induction of disease suppression was limited to specific wheat genotypes. All wheat cultivars examined were uniformly susceptible to infection by the pathogen R. solani AG 8. However, if the pathogen was not introduced to soil until after three successive plantings of the same wheat cultivar, suppression of Rhizoctonia root rot of wheat was observed in the fourth planting, but again only in a wheat genotype specific manner. Wheat cultivars that induced soil suppressiveness to the apple pathogen (R. solani AG 5) induced soil suppressiveness to the wheat pathogen. Wheat genotypes that induced soil suppressiveness enhanced populations of specific fluorescent AG 5 and AG 8 in vitro. These results demonstrate the importance microbial communities and suggest an important role for host genotype in the success of biological control.