Maintenance of MLOs (mycoplasma-like organisms) on <em>Populus alba</em> micropropagation.

Populus alba plantlet micropropagation has been used for maintaining MLOs more than three years in samples collected from infected trees in Paris. Symptoms were observed on plantlets obtained from subcultures of the apical, middle and basal parts of the stems, and from the roots. Fluorescent microscopy failed to detect MLOs in the apical part of the plantlets and showed that they increased near the roots. Electron microscopy confirmed their presence. Some root sieve tubes were completely packed with MLOs. The sensitivity of the two methods used, subculturing and microscopy, for detection of MLOs is discussed. The symptoms remained for one year in plants regenerated from diseased plantlets and grown in the greenhouse. Then they started to disappear. [ABSTRACT FROM AUTHOR]