Mycoplasma-like bodies in plants infected with potato witches' broom disease and the response of plants to tetracycline treatment

The virus origin of a Czechoslovak isolate of potato witches' broom disease is discounted: electron micrographs of ultrathin section of phloem tissues from plants infected with potato witches' broom disease demonstratedMycoplasma-like bodies, spherical or elongated showing binary fission and fragmentation. The minute corpuscles have a diameter of about 50–60 nm, the largest bodies of 1000 nm. The width of elongated filamentous structures is about 200 nm, most oval bodies have a diameter of 250 nm. A weak tetracycline treatment of diseased plants causes a delay of symptom development; a strong dose of tetracycline (applied by means of the wick method into the stem) inhibits symptom appearance completely. Tetracycline produces a phytotoxic effect inhibiting the growth of tomato plants and causing (at higher concentrations) necrosis and death of these plants. There is a note in the paper dealing with the term “mycoplasma”. The word mycoplasma in the sense ofEriksson (1897) or ofMereschkowsky (1910) does not correspond to the genus nameMycoplasma Nowak (1929).