ARS | Publication request: Wheat varietal selection and annual vs. perennial growth habit impact soil microbes and apple replant disease supression

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 18, 2012
Publication Date: January 19, 2012
Citation: Hoagland, L., Mazzola, M., Murphy, K.M., Jones, S.S. 2012. Wheat varietal selection and annual vs. perennial growth habit impact soil microbes and apple replant disease supression. 6th Organic Seed Growers Conference. Meeting Proceedings. 95-100.

Interpretive Summary: The establishment of an orchard on a site previously planted to apple often results in poor tree growth and even death of new trees. This disease phenomenon is termed apple replant disease and typically is controlled through the application of pre-plant soil fumigants, including methyl bromide. In this study, experiments were conducted to examine the use of wheat cover cropping to manage soil microbial communities and enhance growth of apple in replant soils. All soil ecosystems possess a wealth of biological resources with the ability to control plant diseases. Enhancing populations and activity of these organisms has the potential to serve as an environmentally sensitive and biologically sustainable means to control soilborne plant pathogens. This study demonstrated that cultivation of replant soils to certain wheat genotypes enhances populations of resident antagonists resulting in reduced apple root infection by the fungal complex that incites replant disease and improved growth of apple.

Technical Abstract: Wheat can be grown as a cover crop to disrupt soil-borne pathogens and reduce disease in subsequent crops. Modification of the soil microbial community resulting from cover crop cultivation is believed to contribute to decreases in disease incidence. Varietal differences can impact soil microbial community composition, but there has been little effort to actively select for this trait in wheat or develop new varieties with greater ability to suppress soil-borne pathogens. Using soil from an apple orchard with documented pathogen infestation, we evaluated annual wheat genotypes representing historic, high-input and organic selection conditions, as well as wheat genotypes with a perennial growth habit for their capacity to enhance resident microbial antagonists and suppress apple replant disease. Results indicate that selecting wheat genotypes under organic management and further development of perennial wheat will result in new varieties with greater capacity to modify the soil microbial community and suppress soil-borne pathogens. Similar pathogen complexes affect various crop plants, thus findings from these studies are likely to be of value across multiple systems.