Contamination in Plant Tissue Cultures1

In recent years, the possibility of developing numerous plantlets of many plant species in vitro has been realized. Termed plant tissue culture, this method of plant propagation has not been without problems when employed in commercial practice. One problem of major consequence has been bacterial contamination, usually becoming evident during later stages of tissue culture increase and multiplica tion. Present methods of explant disinfestation prior to place ment into culture are often unsatisfactory in completely eliminating bacterial contaminants. Preconditioning of ex plant source plants in cool, dry environments has proved helpful in solving the contamination problem. Studies with Gentamicin®, an antibiotic used in animal tissue cultures, produced results that are unacceptable for plant tissue culture systems. The importance of indexing techniques in development of contaminant free cultures of plants such as dieffenbachias is discussed. Commercial plant tissue culture propagation is an accepted practice in tropical foliage plant production, es pecially in California and Florida. Murashige (3) and other workers have provided the guidelines, techniques, and media formulae that now allow tissue culture propagation of many foliage plant types. Although successful as a propagative technique, plant tissue culture is not without problems. One of the most im portant is culture contamination, especially where caused by bacteria. Even with the most careful workers, bacterial contamination may appear in Stage II, the multiplication stage in Murashige's scheme for production (3). It has been shown (1) that a high percentage of seemingly noncontaminated plantlets of Dieffenbachia maculata 'Perfec tion' Schott. still contained bacteria. Knauss and Miller (2) in studies on bacterial contaminants from several commer cial plant tissue cultures found several isolates to be the plant pathogen, Erwinia carotovora L. R. Jones, and further investigation revealed these isolates to be pathogenic to chrysanthemum cuttings and fern tissue cultures. The research to be discussed in this report was initiated to investigate in more detail culture contamination and to develop procedures to reduce or eliminate this problem. Materials and Methods