Mycoplasma development and cell alterations in white clover affected by clover dwarf an electron microscopy study |
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Authors: | Giuliana Lombardo Maria Bassi F. M. Gerola |
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Affiliation: | (1) Present address: Istituto di Scienze Botaniche, Università di Milano, Milan, Italy;(2) Politecnico di Milano, Centro di Microscopia Elettronica, Milan, Italy |
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Abstract: | Summary The presence of mycoplasma has been demonstrated in the phloem of leaves of white clover (Trifolium repens L.) affected by clover dwarf. Mycoplasma-like bodies were found both in parenchyma and companion cells and in sieve elements.In young parenchyma and companion cells mycoplasma-like bodies appeared as round or oval particles with high ribosomal content, delimited by a ribosome-bearing membrane. Their diameter ranged between 50 and 400 nm. In mature sieve elements they were larger, more pleomorphic, and showed a central clear area containing presumed DNA filaments. Budding and dividing forms were sometimes seen among them.The main alterations found in the infected cells were: increased ribosome content, dilation of the perinuclear space, degeneration of mitochondria and chloroplasts, and cytoplasmic vacuolation. Many cells appeared completely disrupted and their content was replaced by a great number of pleomorphic mycoplasma.This investigation was supported by a grant of Consiglio Nazionale delle Ricerche, Rome. |
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