Abstract

Studies of the interaction of genes and gene products of the Fire Blight pathogen, Erwinia amylovora , and its important host apple resulted in the identification of several genes whose subsequent manipulation in apple resulted in substantial resistance to Fire Blight in research trials.

Issue

Fire Blight is an often devastating, although sporadic disease of apples and related fruits in New York, the United States and international areas. Some consider it the "black death" of pear and apple trees. In some years, it causes millions of dollars of losses. Existing control measures, developed over more than 200 years, are not very effective, are difficult and expensive to use, and may be harmful to the environment. Clearly, more effective and safer means of alleviating the disease for the benefit of producers, consumers of apples and the general public are needed. Our current approach takes advantage of the known interactions between the plant and the pathogen. In preliminary trials, genetic manipulation of several selected genes in apple, resulted in reductions in the susceptibility of the host plant.

Response

Cornell Plant Pathologists in Ithaca, NY, have identified one pathogen and two sorts of apple genes, whose manipulation offers promise to result in reductions in Fire Blight susceptibility. The genes, known as hrpN and dspE, are needed by the pathogen to cause Fire Blight. Although their precise function is not known, we reasoned that the gene products, the proteins HrpN and DspE, interact with proteins of apple. Indeed, we found that specific apple proteins do interact with the bacterial proteins. Further, we hypothesized that if the interacting apple proteins are not present, no interaction can take place and this lack would thwart the development of Fire Blight. To reduce or eliminate the presence of the apple-interacting protein, in close collaboration with Plant Pathologists at Geneva, NY, we used gene silencing techniques in transgenic apples. Recent data from DspE-interacting proteins indicate that some transgenic lines are greatly reduced in susceptibility to Fire Blight infection. Experiments to "turn off" the HrpN interacting proteins are in progress. The third approach also involves the hrpN gene. If the HrpN protein is sprayed on a variety of plants, including apple, the plants develop systemic acquired resistance within a few days. In the third approach, transgenic apples were developed that produce harpin in response to inoculation with the fire blight pathogen. Some of the transgenic lines have exhibited substantial resistance to fire blight.

Impact

Although practical impact of the technology described is yet to be realized, and further research and much development work is needed prior to implementation, the potential impact is great. If Fire Blight is managed with the newly developed gene turn-off or addition methods, the need for pesticides to control Fire Blight will be reduced or eliminated. This would be a boon to producers, consumers and the general public, and would improve fruit production without the risk of a devastating disease or the use of questionable pesticides. This should result in better health through improved nutrition and preservation of the environment.

Funding Sources

• Other USDA (e.g., Water Quality, Special Grants, NRI)
• Eden Bioscience royalty funds

Collaborators

• H. S. Aldwinckle (Collaborator) Department of Plant Pathology, NYSAES, Cornell University, Geneva NY

Key Personnel

• Jean M. Bonasera, (Research Support Specialist II)
• Department of Plant Pathology, Cornell University, Ithaca, New York
• Chang-Sik Oh, (Graduate Research Assistant), Department of Plant Pathology, Cornell University