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Field Detection of Citrus Blight Using Immunological Techniques. M. G. Bausher, USDA-ARS, Horticultural Research Laboratory, 2120 Camden Road, Orlando, FL 32803. M. J. Sweeney, Department of Molecular Biology and Microbiology, University of Central Florida, Orlando 32816. Plant Dis. 75:447-450. Accepted for publication 2 October 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991. DOI: 10.1094/PD-75-0447.

Eighty-six sweet orange trees from three Florida grove locations were diagnosed as being healthy or blighted using a western blot system with proteins extracted from citrus leaves. Extracted proteins were separated on 18% SDS-PAGE gels, electroblotted onto polyvinylidenedifluoride membrane, and probed with citrus blight antisera obtained from blighted citrus trees. This blot system was as reliable as conventional diagnostic systems and in several cases detected the presence of blight before increased tissue concentrations of zinc, decreased water uptake, and wilt were observed. Results were the same for samples taken during winter dormant periods and samples taken during spring growth. The use of leaf samples for the diagnosis of citrus blight has the advantage of allowing repeated sampling, unlike xylem zinc analysis and water injection techniques.