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Etiology

Purification and Infectivity of the Coconut Cadang-cadang Viroid. 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; R. Bautista(2), G. Buenaflor(3), and J. S. Imperial(4). (2)(3)(4)FAO/UNDP Coconut Project, Philippine Coconut Authority, Albay Research Centre, Guinobatan, Albay, Philippines 4908. Phytopathology 75:79-83. Accepted for publication 12 July 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-79.

A procedure is described for the extraction of cadang-cadang viroid RNAs (cc RNA) from infected coconut leaves and their purification by three cycles of polyacrylamide gel electrophoresis. The fast and slow forms of cc RNA-1 (246 and 287 residues, respectively) and the fast form of cc RNA-2 (492 residues) were all infectious. There was no significant difference between the infectivities of the fast forms of cc RNA-1 and -2 and between linear and circular forms of cc RNA-1. The fast form of cc RNA-1 (246 residues) was significantly more infectious (P <0.001) than the slow form (287 residues) from the same palm; the extra repeated segment of 41 nucleotide residues reduced infectivity of the cc RNA significantly. Therefore, the fast form appears to be the basic infectious unit of the cadang-cadang viroid RNAs and is designated to be the coconut cadang-cadang viroid.