Mycoplasmalike Organism Found in the Phloem of Bunch-Diseased Walnuts
Abstract:Walnut bunch is a yellows-type of witches'-broom disease occurring on Japanese, Manchurian, English, native black walnut, and butternut. An electron-microscope study of the phloem tissues of walnut revealed the presence of a mycoplasmalike organism (MLO) in diseased but not in healthy leaf and stem phloem cells. The MLO are pleomorphic, vary in length from 150 to 1000 nm, and are enclosed in a plastic trilaminar unit membrane. Spherical or oval shapes predominate, but tubular forms were also evident near sieve plates. Some sections clearly showed the presence of ribosome- and DNA-like material within MLO cells. The apparent absence of virus particles, together with the consistent association of MLO in diseased but not in healthy walnuts, suggests MLO as a likely causal suspect. The possible relationship of walnut bunch and pecan bunch disease is discussed. Forest Sci. 22:144-148.
Document Type: Journal Article
Affiliations: Principal Plant Pathologist, USDA Forest Service, Northeastern Forest Experiment Station, Delaware, Ohio
Publication date: June 1, 1976
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- Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.
Forest Science is published bimonthly in February, April, June, August, October, and December.
2015 Impact Factor: 1.702
Ranking: 16 of 66 in forestry
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