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The Ultrastructure of a Rickettsialike Organism from a Peach Tree Affected with Phony Disease. George Nyland, Plant Pathologist, University of California, Davis 95616; A. C. Goheen(2), S. K. Lowe(3), and H. C. Kirkpatrick(4). (2)Staff Research Associate IV., University of California, Davis 95616; (3)Research Plant Pathologist, USDA, Agricultural Research Service, Davis, California 95616; (4)Research Plant Pathologist, USDA, Agricultural Research Service, Byron, Georgia. Phytopathology 63:1275-1278. Accepted for publication 5 April 1973. DOI: 10.1094/Phyto-63-1275.

Electron microscopy revealed a rickettsialike organism in vessels of roots of a peach tree affected with phony disease. None was found in similar roots from four nearby healthy trees. The most prominent feature of the cells of the organism is the circumferential folds of the outer wall which are oriented in a regular annular or spiral pattern. In thin sections the outer wall appears notched, wavy, or rippled. The cells are about 2.3 µ × 0.35 µ, slightly smaller than a similar organism associated with Pierce’s disease in grape. A double-layered outer wall and a double-layered cytoplasmic membrane surround the cell contents which appear similar to those illustrated for rickettsiae. A matrix seems to surround some groups of cells. Strands that appear made up of subunits protrude from the outer wall or lie free among the cells. Also among the cells are particles about 28-nm diam that occur singly, in short chains, or clusters. These may be broken portions or subunits of the strands.