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Managing Plant Microbe Interactions in Soil to Promote Sustainable Agriculture

Objective

<O> <LI> To identify and characterize new biological agents, microbial community structure and function, naturally suppressive soils, cultural practices, and organic amendments that provide control of diseases caused by soilborne plant pathogens. <LI> Implement sustainable management strategies for soilborne pathogens that are biologically based and compatible with soil health management practices.

More information

NON-TECHNICAL SUMMARY: The future of sustainable agriculture in the U.S. will increasingly rely on the integration of biotechnology with traditional agricultural practices. Although genetic engineering promises enhanced yields and disease resistance, it is also important to recognize that plants exist in intimate associations with microorganisms, some of which cause plant disease while others protect against disease. Identifying, understanding and utilizing microorganisms or microbial products to control plant disease and enhance crop production are becoming more central parts of sustainable agriculture. Biological control or biologically-based pest management (BBPM) has the potential to control crop diseases while causing no or minimal detrimental environmental impact. For this proposal, we define biological control as the manipulation of microbial populations through cultural, physical or biological means including plant mechanisms. Some of the benefits of utilizing microorganisms include: reduced dependence on chemical pesticides, which is important because of expanding demand for organic produce and increasing costs of such petroleum-based inputs; lack of development of pathogen resistance to biological control organisms, important due to the observed increase in resistance to many chemical controls; more selective action against pathogens and not against beneficial organisms; biodegradability of microbial pesticides and the by-products of their manufacture; reduced danger to humans or animals; improvement of soil quality and health; increased food safety; long term solutions for management of soilborne pathogens; management of diseases in natural ecosystems. During the past project period, W-1147 made major contributions towards our understanding of microbial biological control of plant disease. Such understanding is necessary for expanding the adoption of pest management strategies that employ native and applied biological controls. Demand for biopesticides has continued to expand dramatically in the last five years, and the biopesticide industry is expected to double or triple in the next five to ten years (International Biocontrol Manufacturer's Association, 2004). This expansion is evidenced by the Biopesticide Industry Alliance, established in 2001, which had 31 member companies in 2006. This growth has been driven by expanding organic markets as well as increased public sensitivity to the risks and hazards of chemical pesticides. To date several dozen commercial biocontrol products and processes have been registered by the EPA: over half of these were registered in the last five years. These include fifteen bacterial and seven fungal products, and three activators of plant defenses (http://www.apsnet.org/online/feature/biocontrol/). Basic research into the physiology and genetics of biocontrol microbes will continue to be needed. <P>APPROACH: Objective 1: To identify and characterize new biological agents, naturally suppressive soils, cultural practices, and organic amendments that provide control of diseases caused by soilborne plant pathogens. A. Assessing isolated microbes for biocontrol activity. Experiments in controlled and field environments will focus on representative strains of these new taxa to determine their efficacy. Tables 5-7 show some of the biocontrol agents that are being investigated by W-1147. B. Examining naturally suppressive soils. we employ a population-based approach. Microbial communities can be examined using a variety of culture or culture-independent methods. Different levels of suppressiveness can be created by manipulating the microbial communities with physical, chemical and biological methods such as heat treatments, antimicrobial agents, and nutritional or microbial amendments. Alternatively, naturally occurring soils with different levels of suppressiveness can also be utilized. The relative abundance of each axon can then be associated with levels of suppressiveness. A few examples include Borneman and Becker's work, which identified fungi involved in soils that naturally suppress two important plant pathogens: sugarbeet cyst and root knot nematodes. Paulitz has documented the influence of agricultural practices on Rhizoctonia suppressiveness and characterized shifts in bacterial communities associated with such practices. McSpadden Gardener has recently discovered bacteria associated with general disease suppression arising from the application of different organic field management strategies. C. Examining cultural practices that influence soilborne pathogens. Members of the W-1147 workgroup have performed numerous experiments examining how agricultural practices influence soilborne pathogens. For example, soil samples collected from various grower fields were assessed for their general suppressive capacity to soilborne pathogens (root health) using a soil bioassay with bean. In general, root health was improved with the implementation of reduced tillage, long rotations with grain crops, certain cover crops and organic amendments. Researchers (ARS-WA) have explored how tillage affects root diseases, and how they can be managed with crop rotation, fallow, and proper herbicide application to control reservoirs of inoculum from crop volunteers and weeds. They have also initiated research characterizing the microbial communities from these suppressive soils and to assess the mechanism(s) involved OBJECTIVE 3: Implement sustainable management strategies for soilborne pathogens that are compatible and integrated with good soil health practices. Intensive production of agronomic crops has contributed to gradual deterioration of soil health, resulting in reduced yield and profitability. Characteristics of deteriorated soils include crusting, compaction, low content of organic matter, the increased incidence and damage of root diseases caused by soilborne pathogens, and the prevalence of other pests. In addition, it is well documented that damage due to diseases caused by soilborne pathogens is greater in poor quality and unhealthy soils.

Investigators
Hao, Jianjun
Institution
Michigan State University
Start date
2008
End date
2013
Project number
MICL04040
Accession number
215804