New strategies are needed for controlling fire blight. Progress 07/01/05 to 06/30/07 Outputs Severe fire blight epidemics in 19 contributed significantly to this reduction in the size of the Michigan apple industry. This approach is designed to confer resistance in apple to fire blight in a novel manner. We intend to identify the region of DspE that binds to DspF, and also express DspF in apple cells to see if the protein would bind DspE in apple, and disarm the protein. DspF is hypothesized to bind to DspE in the fire blight pathogen to aid in effective secretion of DspE into plant cells. Attempts to disarm the virulence effector DspE in apple will involve a novel approach using the chaperone protein DspF. We will again use gfp-tagged cells so that infection can be followed microscopically. Virulence assays with mutants will be conducted in immature pear fruit, flowers, and actively-growing shoots. We will construct knockout mutants in the type II structural genes and in the levansucrase and polygalacturonase genes to evaluate the system in a general sense and the role of The identification of genes encoding a type II secretion system and of enzymes known to be secreted via the type II pathway highlights a potentially under-appreciated aspect of E. We will also assess the role of host resistance in limiting shoot blight infection in field experiments. This work will help us assess why actively-growing shoots are most susceptible and why prohexadione-calcium treated trees are more resistant to shoot infection. amylovora wild-type and mutant strains marked with gfp fluorescence. We will examine the progression of infection at a microscopic level using E. prohexadione-calcium,įertilization) in promoting or inhibiting infection, and understanding the genetic basis of the impact of apple varietal susceptibility on shoot blight infection and spread of fire blight within trees. This is new research to be initiated in FY 05 and focused on developing a mechanistic understanding of shoot blight infection at the organism, cellular, and genetic level with a goal of finding and developing new control options including identifying and eliminating inoculum sources, the role of treatments that affect tree vigor (ex. In addition, we will initiate work to examine the shoot blight phase of the fire blight disease. The evaluation of the efficacy of a number of chemicals against fire blight may provide possble short-term solutions to this important disease. The focus of the field research work for 2005 is to increase the efficacy of biological control treatments against fire blight and to evaluate the efficacy of gentamicin in the control of streptomycin-resistant strains of E. Project Methods Orchard trials will be carried out to evaluate new bactericides and chemical control strategies for fire blight control.
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