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Association of Two Ribonucleic Acid Species with Cadang-Cadang Disease of Coconut Palm. J. W. Randles, Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, South Australia 5064; Phytopathology 65:163-167. Accepted for publication 6 August 1974. DOI: 10.1094/Phyto-65-163.

Coconut palms with cadang-cadang, a disease of suspected viral etiology, contain two apparently disease-specific RNA species of low molecular weight. A survey of coconut palms, within and outside the area where the disease is known to occur, has shown that the two RNA species are found only in nucleic acid extracts of diseased palms, not in normal or stressed (but nondiseased) palms. They can be detected just before symptoms appear in developing young fronds, and are then retained as the leaves mature. They can also be detected at early, mid-, and late stages of disease development, and therefore may be useful in the diagnosis of the disease. It is suggested that these RNA species may be components of the presumed cadang-cadang pathogen, and one of them, with a molecular weight of 84,000 daltons, a sedimentation coefficient of 7.5S, and a thermal denaturation curve with an approximate 10% hyperchromic shift at about 58 C, is similar to known members of the viroid group of pathogens. Failure to find conventional virus particles in preparations from which the disease-specific RNA’s were obtained, and the sensitivity of the disease-specific RNA species to low concentrations of ribonuclease before deproteinization of preparations, supports the view that a viroid hypothesis for cadang-cadang disease should be seriously considered.

Additional keywords: yellow mottle decline, viroid hypothesis, diagnosis.