Biological control and etiology of apple replant disease

2007 Impact statement
  • Merwin, Ian Alexander

abstract

Apple replant disease occurs worldwide and was previously controlled by methyl bromide soil fumigation. We have been testing non-chemical methods for controlling this serious disease problem, and studying the microbial bases for its causation and control. Our recent work has shown that several new rootstocks developed at Cornell have substantial resistance to this soil-borne disease, and may eliminate the need for soil fumigation.

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issue being addressed

Apple replant disease is a major problem wherever apples are grown. Soil fumigation with methyl bromide or other biocides that control this disease is expensive, dangerous to farmers, and damaging to the earth`s protective ozone layer. Using natural genetic resistance in apple rootstocks to control this disease can save lives, protect the environment, and ensure that fruit growers can renovate their orchards effectively and economically.

response

We used DNA fingerprinting methods and field experiments to determine which apple rootstocks were resistant to replant disease, and how or why they were resistant. We found that certain rootstock genotypes induce beneficial or disease suppressing microbial communities in the rhizosphere. We identified these rootstocks, and their characteristic microbial communities. Cloning and sequencing methods in conjunction with GenBank searches enabled us to identify which soil microbes occured on healthy and diseased apple root systems.

impact assessment

Apple is an important fruit crop in New York, ten other U.S. states and several dozen countries worldwide. Replant disease is a significant problem in all these regions, and our research demonstrated that it could be controlled safely and effectively by selecting orchard rootstocks with natural genetic resistance. There is considerable interest in this work, and major fruit-tree nurseries are rapidly propagating these new Cornell rootstocks and making them available to the tree-fruit industry.

academic priority area

has geographic focus

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funding source description

  • Multistate
  • Toward Sustainability Foundation
  • New York State Department of Agriculture and Markets
  • National Research Initiative
  • USDA-Eastern Viticulture Consortium
  • Hatch

collaborators

  • Dept. of Crop and Soil Science, Cornell
  • Dept. of Plant Pathology, Cornell
  • Dept. of Horticultural Science, NYSAES Geneva

key personnel

  • Eric Nelson
  • Michael G. Brown
  • Janice E. Thies
  • Gennaro Fazio

mission focus

From CALS annual faculty reporting. Imported on August 5, 2008