A monoclonal antibody was produced by using enriched antigen from an infected chokecherry plant, and was used to detect the X-disease phytoplasma using both ELISA and immunofluorescence staining. The monoclonal antibody reacted with five of seven tested phytoplasmas in the X-disease phytoplasma cluster, and one of four phytoplasmas (pigeon pea witches'-broom phytoplasma) outside that cluster. The efficiency of the monoclonal antibody for detection of X-disease phytoplasmas was verified through assays of infected stone fruit plants. The efficacy of the monoclonal antibody was confirmed by X-disease phytoplasma-specific nested-polymerase chain reaction. Development of the monoclonal antibody represents a substantial improvement in the potential for commercial diagnosis of X-disease phytoplasma infection in nurseries and orchards and for screening large numbers of stone fruit plants for X-disease phytoplasma infection in breeding programs.

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Author notes

This project was supported in part by a grant from USDA-SCS North Dakota Centennial Windbreak Project and USDA-NRICGP grant 9504248 and NDSU McIntire-Stennis Project ND6208 and ND6206. We acknowledge the assistance of Dr. E. Berry, NDSU Monoclonal Antibody Laboratory, and M. Draper, NDSU Plant Pest Diagnostic Laboratory. We thank Dr. T.A. Chen, Rutgers University, New Brunswick, NJ, Dr. B.C. Kirkpatrick, University of California-Davis, Davis, Drs. W.A. Sinclair and R.L. Andersen, Cornell University, Ithaca, NY, Dr. C.J. Chang, University of Georgia, Griffin, Dr. U. Rahardja, Michigan State University, East Lansing, and Dr. N.A. Harrison, University of Florida, Fort Lauderdale, for providing experimental phytoplasmas and stone fruit tissues. We also acknowledge the assistance of W.A. Sargent and Drs. R.G. Novy, J.B. Rasmussen and J.R. Venette for helpful review comments.

2Former Graduate Research Assistant.

3Associate Professor.

4Research Associate. Department of Plant Pathology, North Dakota State University Fargo, ND 58105

5Professor. Department of Horticulture, Nanjing Agri. University, Nanjing, Jiangsu Prov., P. R. China 210095.