VIROID-LIKE RNA ASSOCIATED WITH APPLE SCAR SKIN (OR DAPPLE APPLE) DISEASE

Authors:	H. Koganezawa, H. Yanase, T. Sakuma
Abstract: The close relationship between apple scar skin and dapple apple disease was suggested by Yamaguchi and Yanase (1976), but the causal agent has not been identified. In order to test the viroid etiology for the disease, nucleic acid was isolated from apples infected with scar skin or dapple apple disease by the combined methods used for isolating viroids. Electrophoresis in polyacrylamide gels showed two bands (RNA 1 and RNA 2) which were not detected in extracts from healthy fruit. RNA 1 was a fast moving band and was detectable in extracts from both mature and young fruit showing scar skin, cracking or dapple symptoms. The migration behavior in the electrophoresis of RNA 1 was similar to that of known viroids. RNA 2 was a slow moving band and detectable only in extracts from young fruit showing scar skin symptoms. The unusual nucleic acid component as mentioned above was not detectable in extracts from apple fruit affected by 'Kikei-ka' (green crinkle) disease. Those results suggest a common viroid etiology of apple scar skin (or dapple apple) disease.
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