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Disease Detection and Losses

Detection and Concentration of Coconut Cadang-Cadang Viroid in Coconut Leaf Extracts. N. A. Mohamed, FAO/UNDP Coconut Project, Philippine Coconut Authority, Albay Research Centre, Guinobatan, Albay, Philippines 4908, Present address: Ministry of Agriculture, Plant Health Diagnostic Station, P.O. Box 24, Lincoln, New Zealand; J. S. Imperial, FAO/UNDP Coconut Project, Philippine Coconut Authority, Albay Research Centre, Guinobatan, Albay, Philippines 4908. Phytopathology 74:165-169. Accepted for publication 27 July 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-165.

Procedures for the detection of coconut cadang-cadang viroid (CCCV) by polyacrylamide gel electrophoresis (PAGE) and molecular hybridization with ³H- or ³²P-labelled complementary DNA (cDNA) are compared. The lower limits of detection per assay for the three techniques were: PAGE, 50 ng; ³H-cDNA hybridization in solution, 0.5 ng; ³²P-cDNA spot hybridization on nitrocellulose membranes, 0.25 ng. Spot hybridization was considered the best for routine diagnosis of CCCV because of its sensitivity, ease of operation, and reliability. Infection in inoculated seedlings could be detected by this method at least 4 mo before the viroid band was detectable by PAGE. Concentrations of CCCV in partially purified nucleic acid extracts were estimated by molecular hybridization and measurements of yields of purified viroid. In the same palm, young fronds contained lower amounts of CCCV than mature fronds. Palms in the early and medium stages of disease contained similar amounts of CCCV while late stage palms contained lower amounts. Palms at the same stage of disease from varied geographical locations with different levels of disease incidence contained comparable levels of CCCV.