Contamination Problems

Typical disinfecting agents used to get rid of contamination are:

• sodium hypochlorite (commercial bleach)

• calcium hypochlorite (pool disinfecting agent)

• sodium   dichloroisocyanurate  [NaDCC] (pool disinfecting agent)

• hydrogen peroxide

• PPM (Plant Preservative Mixture)
  

Solving Subculture Contamination Problems

• Plantlets growing in culture are often contaminated but do not exhibit characteristics of contamination

• Upon subculture the contaminants are shaken loose or other wise disrupted and grow.  End result:  contamination

• To avoid this, the following can be done:

  • Dip each explant to be subcultured in a solution of 1 ml PPM plus 50 ml water (or 5 ml in one cup water).  The diluted PPM container should be in the hood or cleanbox.  Using a sterile forceps, aseptically remove the explant from the mother culture, dip it in the PPM solution, and then transfer to fresh media WITHOUT rinsing off the PPM

  • Solutions of NaDCC can be used in the same way but tend to be harsh on explants so one must experiment with the proper concentration.   The advantage is that NaDCC is cheaper than PPM, but PPM is gentler on the explants than other agents.

  • Solutions of 5-10% commercial may also be used for this purpose but these may also be harsh and experimentation is needed.