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Effectiveness of the Chromatographic Method for Detecting Exocortis Virus Infection in Poncirus trifoliata. A. W. Feldman, University of Florida, IFAS, Agricultural Research and Education Center, Lake Alfred 33850; G. D. Bridges(2), R. W. Hanks(3), and H. C. Burnett(4). (2)(4)Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Winter Haven 33880; (3)University of Florida, IFAS, Agricultural Research and Education Center, Lake Alfred 33850. Phytopathology 61:1338-1341. Accepted for publication 1 June 1971. DOI: 10.1094/Phyto-61-1338.

Free and bound forms of scopoletin and umbelliferone accumulate in the bark of Poncirus trifoliata (at the bud union) within 3 years after budding with a citrus exocortis virus-infected (CEV) scion. These coumarins, detected by thin-layer chromatography (TLC), were used to ascertain CEV infection in the candidate scion. Effectiveness of the TLC method for detecting CEV in candidate trees was compared with the phloroglucinol-HCl color test and with the standard citron (Citrus medica L.) indexing. Percentage of correct diagnoses by TLC (using data from citron indexing as a standard) was highest (90%) when extracts were prepared from P. trifoliata bark collected in May and June. Diagnoses were correct in 70% of samples collected in April and July, and in 55% of samples collected in October. Scion variety did not appear to modify the specific coumarins that accumulated in the CEV-infected P. trifoliata bark or affect their detection by TLC. Infection with xyloporosis, tristeza, or psorosis virus(es) did not cause accumulation of coumarins in P. trifoliata bark. Phloroglucinol-HCl color tests correlated closely (ca. 90%) with the citron index standards only when the candidate trees had been budded for less than 8 years.