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Etiology

Spiroplasmas from Plants with Aster Yellows Disease and X-Disease: Isolation and Transmission by Leafhoppers. Boligala C. Raju, Department of Plant Pathology, University of California, Davis 95616, Current address of senior author: Yoder Brothers, Inc., Box 68, Alva, FL 33920; Alexander H. Purcell(2), and George Nyland(3). (2)Department of Entomological Sciences, University of California, Berkeley 94720; (3)Department of Plant Pathology, University of California, Davis 95616. Phytopathology 74:925-931. Accepted for publication 6 March 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-925.

Spiroplasma citri was isolated infrequently in vitro from surface-sterilized plants affected with aster yellows (AY) disease and from aster leafhoppers, Macrosteles severini (= M. fascifrons), that had fed on AY-affected Plantago. Similarly, spiroplasmas were isolated from celery, cherry, and peach affected by X-disease and from leafhoppers (Colladonus montanus) that had fed on X-diseased celery. No spiroplasmas were isolated from plant, insect, or media controls. In transmission trials, M. severini was injected with spiroplasmas that had been cultured from AY-diseased plants. Similarly, the leafhoppers C. montanus and Scaphytopius nitridus were injected with spiroplasma from X-diseased plants. No apparent transmissions occurred with most isolates (AY, 36 isolates and X-disease, 23 isolates). However, typical AY and X-disease symptoms were produced in Plantago and celery, respectively, with three separate uncloned isolates from AY-diseased plants and with three uncloned isolates from X-diseased plants. Plants with typical AY or X-disease symptoms were good sources for efficient leafhopper transmission, but spiroplasmas were only infrequently cultured in many attempts. Some spiroplasma isolates from AY-affected plants or X-diseased plants caused disease symptoms that were not typical of either AY or of X-disease in Plantago or celery, respectively. A spiroplasma was isolated readily from plants with “atypical” symptoms, but none of the three species of leafhoppers that were tested transmitted spiroplasma after acquisition feeding on “atypical” plants. Spiroplasma isolates reacted identically to Spiroplasma citri in spiral deformation and growth inhibition tests. S. citri from stubborn-affected oranges injected into C. montanus and S. nitridus, which subsequently inoculated celery, induced disease symptoms distinct from either “atypical” symptoms or from symptoms of AY or X-disease.