ISHS Acta Horticulturae 225: Bacterial and Bacteria-like Contaminants of Plant Tissue Cultures
CONTROL OF ACCIDENTAL CONTAMINATIONS DURING MASS PROPAGATION |
| Authors: | Ph. Boxus, J.M. Terzi |
| Abstract:
The present report covers twelve years of observations carried out in our laboratory, which produced an annual average of one million plants. The sterilisation of the culture media at 110°C, the insufficient flaming of the tools as well as the use of contaminated alcohol undoubtedly play a large part in the selection and spread of resistant bacterial lines. In propagation media, many contaminants remain latent allowing the plants to grow more or less normally. In order to reveal them, peptone (265 mg/l) and yeast extracts 88 mg/l) are added. In these conditions, examination based on transparency or the turbidity of the condensation water at the agar surface enables detection and removal of the contaminated flasks. Contaminants, more virulent in rooting media, are likely to be lethal for the young trees propagated in vitro. Yet, the addition of kinetin (0.5 mg/l) to these media enables a nearly normal development of the young plantlets without inhibiting root induction. In the course of twelve years of mass production, mainly of strawberry plants and woody species, problems caused by bacterial contaminants were to be faced in increasing numbers. As previously mentioned, they were difficult to detect and unconsciously transmitted by workers (Boxus and Terzi, 1987). Culture media were always autoclaved for 20 minutes at 110°C only. Yet, in 1979, the selection of a more thermostable germ involved doubling of autoclaving duration. Later on, stocks fully contaminated by bacteria (not easily detectable), resistant to instrument flaming and able to survive for a few hours, at least in alcohol, were increasingly observed (Boxus and Terzi, 1987). The bacteria present in some of these stocks, also frequently isolated in medical bacteriology laboratories, were always identified as non-phytopathogenic and often considered as water and soil contaminants. Yeasts were sometimes identified. Here, the fermentation smell liberated enabled rapid detection. The main contaminants identified were: Acinetobacter, Corynebacterium, Enterobacter (Erwinia), Flavobacterium, Pseudomonas, Torulopsis glabrata. | |
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