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We have elected to initiate this integrated research and outreach activity to tackle fire blight disease and provide solutions, both short- and long-term, to this important agricultural problem using a multidisciplinary approach.<P> Our short-term goal is to develop environmentally sound and effective methods of management and control for this disease, by capitalizing on 1) state of the art knowledge of the biology of the pathogen, host, antagonists, and inhibitors; and 2) advances in high-technology, in particular nanotechnology, for delivery of control agents. <P>
Our long-term goal is to incorporate genetic resistance into the host, apple, so that apple trees can fight off the pathogen on their own. This will capitalize on 1) expansive genomics resources available for the apple genome; and 2) genomics-based approaches for identifying and characterizing these genes. These isolated gene(s) can then be incorporated in the future into apple using established genetic engineering technologies. <P>
Throughout this project, we will translate project outcomes to beneficiaries of this research, namely growers and consumers, through effective and innovative outreach and educational programs, and we will address the economic benefits and available marketing tools to support adoption of the end products of this integrated genomics and management systems project.<P>
Objectives: <OL> <LI> Evaluate and assess virulence inhibitors against Erwinia amylovora. <LI> Evaluate and enhance efficacy of microbial biocontrol agents. <LI> Controlled and sustained delivery of virulence inhibitors and biocontrol agents mediated by microparticles/nanoparticles. <LI> Identify and clone fire blight resistance genes. <LI> Develop and deliver outreach programs for comprehensive management systems for fire blight. <LI> Develop and assess economic and marketing opportunities for biocontrol of fire blight disease as well as develop fire blight resistant apple varieties.
APPROACH: Since many chemical compounds have been found to be effective against a broad-range of Gram-negative mammalian pathogens, we hypothesize that compounds identified for mammalian systems will also be effective against plant enterobacteria, which share similar type III secretion systems as the main virulence mechanism to cause disease. Experiments will be designed to use known virulence inhibitors effective against mammalian pathogens to test their effectiveness against E. amylovora, both in vitro and in vivo, and to determine the potential molecular mechanisms involved in suppressing the virulence of the pathogen. The mechanisms of the commercially available biocontrol agent, P. agglomerans strain E325, and selected bacterial and yeast antagonists highly effective against E. amylovora in screening tests on blossoms, will be studied using a synthetic medium based partially on the chemistry of flower stigma exudates and using detached crab apple flowers in controlled environments. The effectiveness of strain E325 will be enhanced by altering production and formulation procedures to increase production of an antibiotic highly specific to E. amylovora and to increase the tolerance of E325 to desiccation on flower surfaces. Efficacy of biological control will also be increased by combining E325 with other antagonists with complementary mechanisms and ecological niches. Highly effective antagonist mixtures, virulence inhibitors, or combinations of these agents will be field tested at Wenatchee (WA), Urbana (IL), and East Lansing (MI). Biodegradable and biocompatible materials will be developed for the sustained delivery of virulence inhibitors and biocontrol agents in orchard environments. This will be mediated by microparticles or nanoparticles with optimized size and architecture to facilitate controlled release of the control agents over time. Based on previous studies by various groups identifying QTL for fire blight resistance, the QTL identified from both the crab apple ?Everest? and M. floribunda 821 and located on LG12 of the apple genome will be targeted for identifying gene(s) for resistance to fire blight. Efforts will be made to identify a BAC contig on the apple physical map covering the QTL for fire blight resistance and fine mapping of the QTL region. Following sequencing of the BAC contig, candidate genes will be identified. The function of the genes will be analyzed by transforming plants, through overexpression and knockouts, and transformed plants will be evaluated for fire blight resistance in a greenhouse. New technologies for fire blight management will be delivered to the tree fruit industry through the development of a project website and educational programs covering biocontrol, nanotechnology, and genomics.