ISHS Acta Horticulturae 616: I International Symposium on Acclimatization and Establishment of Micropropagated Plants
DISEASE MANAGEMENT OF MICROPLANTS: GOOD LABORATORY PRACTICE |
| Authors: | A.C. Cassalls, E.A. O´Herlihy |
| Keywords: | Aseptic culture, biotization, contamination, molecular diagnostics, pathogens, pathogen-indexing |
| DOI: | 10.17660/ActaHortic.2003.616.8 |
| Abstract:
The first international conference on bacterial contamination of plant tissue culture was held in 1987, since then there has been a series of conferences on the topic of the health quality of microplants. A consensus emerging from these conferences has been that: rigorous pathogen-indexing should be carried out on the stock plants. Where contamination is detected, pathogen-free escapes should be sought or thermo- or chemotherapy applied. In vivo progeny plants should be rigorously re-screened after therapy to ensure freedom from pathogens. Pathogen-free plants should be maintained under Stage 0 conditions. Cultures should be established preferentially from apical meristems. The excised meristem tips should be of minimal size, should be placed on bacterial expression media and should be rigorously indexed for bacterial contamination before clonal propagations begins. Where meristem culture combined with in vitro therapy is used to eliminate pathogens. Preferentially, progeny plants should be grown in vivo for pathogen-indexing before clonal propagation begins. Mass clonal propagation from aseptic cultures should be monitored for laboratory contamination following HACCP guidelines. Contaminated cultures should be disposed of appropriately or attempts may be made to recover contaminated cultures by transfer to autotrophic culture. A weaning strategy should be devised to protect against the risks of damping-off pathogens. This can be based on promotion of microplant physiological quality and by elicitation of pathogenesis-related proteins and/or by biotization in vitro or immediately post vitrum. Ideally, microplants should be certified as to their freedom from known diseases of the crop and freedom from cultivable contaminant. These guidelines provide a framework for managing contamination in tissue culture. They make the clear distinction between the establishment of aseptic cultures and the management of laboratory contamination. The major problems are still associated with the first stage for there are few crops e.g. potato, where most if not all diseases are characterised and for which diagnostics and diagnostic tests are available. Even for temperate fruit crops e.g. rosaceous fruit crops, not all pathogens have been characterised, nor are commercial diagnostics available for all characterised pathogens. This problem is even greater for the less known crops which are the main subject for micropropagation. A further problem in e.g. woody plants, if the often reported re-emergence in the nursery of pathogens from plants exposed to thermotherapy and indexing negative in in vitro cultures. Here, contamination management in micropropagation will be discussed with emphasis on the development of broad spectrum (non-strain specific or ‘quarantine’) molecular diagnostics and on the validation of in vitro screening using serological and molecular diagnostics. | |
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