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Sweet Potato Little-Leaf (Witches’-Broom) Associated with a Mycoplasmalike Organism. Robert P. Kahn, Plant Pathologist, Agricultural Quarantine Inspection Program (APHS), U.S. Plant Introduction Station (USPIS), USDA, Glenn Dale, Maryland 20769; R. H. Lawson(2), R. L. Monroe(3), and Suzanne Hearon(4). (2)Plant Pathologist, Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705; (3)(4)Agricultural Research Technician, USPIS, USDA, and Microbiologist, Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705. Phytopathology 62:903-909. Accepted for publication 21 February 1972. DOI: 10.1094/Phyto-62-903.

A plant introduction, Ipomoea batatas ‘Nukua Loka’ (P.I. 308200) from New Zealand, originally collected in Tonga, showed little-leaf, proliferation, yellowing, stunting, and witches’-broom symptoms when grown in quarantine at the U.S. Plant Introduction Station, Glenn Dale, Md. Sweet potato russet crack virus (RCV) and a mycoplasmalike organism (MLO) were both detected in P.I. 308200. However, the little-leaf, proliferation, and witches’-broom symptoms were associated with a MLO and not RCV on the basis of electron microscopy, short-term heat therapy, and oxytetracycline sensitivity data. Plants of P.I. 308200 without little-leaf or proliferation symptoms were developed either by heat therapy or oxytetracycline treatment.

Additional keywords: sweet potato viruses.