Progress 08/01/04 to 07/31/06
Outputs
The apple acreage in Michigan has declined by about 18% in the last five years; severe fire blight epidemics in 1998 and 2000 contributed significantly to this reduction in the size of the Michigan apple industry. New strategies are needed for controlling fire blight. The objectives of this proposal are to integrate new control strategies based on growth regulation, boosting the resistance of apple trees, and antibiotics into disease management programs; characterize the genetic variation between Erwinia amylovora and closely related species; evaluate the transgenic expression of the MpNPR-1 gene in apple, and characterization of the Hrp virulence system in E. amylovora. In the 2005-06 report period, we found that streptomycin resistance is becoming more widepsread in Michigan, further limiting the ability of growers to control the disease with the best bactericide available. Streptomycin resistance was detected in the Hart apple-growing area of Michigan, the third (of
four) major apple-growing areas in the state to harbor streptomycin-resistant E. amylovora. We tested the efficacy of the experimental antibiotics gentamicin and kasumin in fire blight control and found that both antibiotics have potential as a subsititue for streptomycin in fire blight management programs. The biological control agents Pantoea agglomerans C9-1 and E325 also performed well in disease control trials performed in 2006. We tested two new compounds, the fungicide famoxate and the plant elicitor laminarin, for control of the blossom blight phase of fire blight. While both of these materials were effective in 2005 under low to moderate disease pressure, the materials did not effectively control blossom blight in 2006 under high disease pressure. The completion of the IVET work, which aimed to identify all of the important E. amylovora genes induced during infection, yielded about 160 genes of interest for further examination. We identified known virulence genes but also
characterized a new effector protein, termed HrpPtoCea. We also identified new potential proteins secreted through a type II secretion system including HecA, a known virulence factor in Erwinia chrysanthemi. We are interested in a large number of transporters that we recovered and determining their role in virulence as well. In addition, we continue to focus our efforts on determining the function of DspE, the critical effector for disease. We found that one of the functions of DspE is to suppress the innate immunity response of plants. Knowledge of the genes expressed by E. amylovora during infection and studies of critical effectors such as DspE now reveals potential targets for novel disease management strategies.
Impacts
Field research evaluating new materials and streptomycin alternatives for fire blight control is critical for the continued management of fire blight on existing apple trees. Research on genes required for virulence of the fire blight bacterium may offer the promise of finding novel control strategies, including the rational design of control compounds for fire blight.
Publications
- Debroy, S., R. Thilmony, Y.B. Kwack, K. Nomura, and S.Y. He. 2004. A family of conserved bacterial effectors inhibits salicylic acid-mediated basal immunity and promotes disease necrosis in plants. Proc. Natl. Acad. Sci. USA 101:9927-9932.
- Zhao, Y., S.E. Blumer, and G.W. Sundin. 2005. Identification of Erwinia amylovora genes induced during infection of immature pear tissue. J. Bacteriol. 187:8088-8103.
- Sundin, G.W., G.R. Ehret, and G.C. McGhee. 2006. Control of fire blight on Jonathan apple in east Lansing, Michigan in 2005. Fungic. Nematic. Tests 61:PF010.
- Sundin, G.W., G.R. Ehret, and G.C. McGhee. 2006. Fire blight control on Gala apple in 2005. Fungic. nematic. Tests 61:PF008.
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Progress 01/01/05 to 12/31/05
Outputs
The apple acreage in Michigan has declined by about 18% in the last five years; severe fire blight epidemics in 1998 and 2000 contributed significantly to this reduction in the size of the Michigan apple industry. New strategies are needed for controlling fire blight. The objectives of this proposal are to integrate new control strategies based on growth regulation, boosting the resistance of apple trees, and antibiotics into disease management programs; characterize the genetic variation between Erwinia amylovora and closely related species; evaluate the transgenic expression of the MpNPR-1 gene in apple, and characterization of the Hrp virulence system in E. amylovora. In the 2005 report period, we found that streptomycin resistance is becoming more widepsread in Michigan, further limiting the ability of growers to control the disease with the best bactericide available. We tested the efficacy of the experimental antibiotic gentamicin in fire blight control and
found that gentamicin has potential as a subsititue for streptomycin in fire blight management programs. The biological control agent Pantoea agglomerans C9-1 also performed well in disease control trials performed in 2005. We tested two new compounds, the fungicide famoxate and the plant elicitor laminarin, and found that both provided levels of fire blight control indistinguishable from streptomycin under low to moderate disease pressure. We will experiment with these control treatments further in 2006. The completion of the IVET work, which aimed to identify all of the important E. amylovora genes induced during infection, yielded about 160 genes of interest for further examination. We identified known virulence genes but also characterized a new effector protein, termed HrpPtoCea. We also identified new potential proteins secreted through a type II secretion system including HecA, a known virulence factor in Erwinia chrysanthemi. We are interested in a large number of transporters
that we recovered and determining their role in virulence as well. In addition, we continue to focus our efforts on determining the function of DspE, the critical effector for disease. We found that one of the functions of DspE is to suppress the innate immunity response of plants. Knowledge of the genes expressed by E. amylovora during infection and studies of critical effectors such as DspE now reveals potential targets for novel disease management strategies.
Impacts
Field research evaluating new materials and streptomycin alternatives for fire blight control is critical for the continued management of fire blight on existing apple trees. Research on genes required for virulence of the fire blight bacterium may offer the promise of finding novel control strategies, including the rational design of control compounds for fire blight.
Publications
- Debroy, S., R. Thilmony, Y.B. Kwack, K. Nomura, and S.Y. He. 2004. A family of conserved bacterial effectors inhibits salicylic acid-mediated basal immunity and promotes disease necrosis in plants. Proc. Natl. Acad. Sci. USA 101:9927-9932.
- Zhao, Y., S.E. Blumer, and G.W. Sundin. 2005. Identification of Erwinia amylovora genes induced during infection of immature pear tissue. J. Bacteriol. 187:8088-8103.
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Progress 01/01/04 to 12/31/04
Outputs
The apple acreage in Michigan has declined by about 18% in the last five years; severe fire blight epidemics in 1998 and 2000 contributed significantly to this reduction in the size of the Michigan apple industry. New strategies are needed for controlling fire blight. The objectives of this proposal are to integrate new control strategies based on growth regulation, boosting the resistance of apple trees, and antibiotics into disease management programs; characterize the genetic variation between Erwinia amylovora and closely related species; evaluate the transgenic expression of the MpNPR-1 gene in apple, and characterization of the Hrp virulence system in E. amylovora. In the 2004 report period, we found that streptomycin resistance is becoming more widepsread in Michigan, further limiting the ability of growers to control the disease with the best bactericide available. We tested the efficacy of the experimental antibiotic gentamicin in fire blight control and
found that gentamicin has potential as a subsititue for streptomycin in fire blight management programs. The biological control agent Pantoea agglomerans C9-1 also performed well in disease control trials performed in 2004. We will experiment with these control treatments further in 2005. The completion of the IVET work, which aimed to identify all of the important E. amylovora genes induced during infection, yielded about 160 genes of interest for further examination. We identified known virulence genes but also characterized a new effector protein, termed HrpPtoCea. We also identified new potential proteins secreted through a type II secretion system including HecA, a known virulence factor in Erwinia chrysanthemi. We are interested in a large number of transporters that we recovered and determining their role in virulence as well. Knowledge of the genes expressed by E. amylovora during infection now reveals potential targets for novel disease management strategies.
Impacts
Research on genes required for virulence of the fire blight bacterium may offer the promise of finding novel control strategies, including the rational design of control compounds for fire blight. These strategies will ultimately impact host resistance, a disease management strategy that is environmentally friendly and should prove durable.
Publications
- No publications reported this period
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