Department of Plant Protection, Fujian Agriculture and Forest University, Fuzhou, Fujian 350002, P. R. China
Biologist, Indian River Research and Education Center, University of Florida, Fort Pierce 34945
Professor, Indian River Research and Education Center, University of Florida, Fort Pierce 34945
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Accepted for publication 18 December 2001.
Ten grapefruit trees that had been inoculated with a mild isolate of Citrus tristeza virus (CTV) and maintained in the field for 18 years were found in a previous study to be declining and infected with severe isolates of CTV, or symptomless and infected with mild isolates of CTV, using enzyme-linked immunosorbent assay (ELISA). They were assayed with an in situ immunoassay (ISIA) procedure using monoclonal antibodies 17G11 (reacts with most Florida isolates of CTV) and MCA13 (reacts with severe, but not Florida mild isolates of CTV). All the grapefruit trees were 17G11 positive by ELISA and ISIA. The five trees that showed moderate decline symptoms were MCA13 positive by ELISA and ISIA. The five symptomless trees were MCA13 negative by ELISA. However, four of the five symptomless trees were MCA13 positive by ISIA, which showed that ISIA with MCA13 had greater sensitivity in detecting severe CTV isolates than ELISA. These results suggested that the cross-protected grapefruit trees, regardless of symptoms, were infected with both mild and severe isolates of CTV.
© 2002 The American Phytopathological Society