DECONTAMINATION OF KAVA (PIPER METHYSTICUM) FOR IN VITRO PROPAGATION

Abstract

The major constraint to kava (Piper methysticum) tissue culture is endogenous contaminants. Despite stringent surface sterilisation procedures, decontamination has been unsuccessful in the past. In view of this problem, which prevents the establishment of kava in vitro, different approaches to decontamination have been investigated. The first approach involved growing kava plants in a glasshouse and applying 8-hydroquinoline with various concentrations of BAP to induce new shoots. Once new shoots had been initiated the plants were sprayed weekly with a solution containing a fungicide (Benlate) and an antibiotic (rifampicin). It was thought that the combination of chemicals would alleviate the problems of endogenous contaminants. However, the use of explants from treated plants and new shoots were both unsuccessful. The second approach involved the use of antibiotics in sterilization procedures and the incorporation of antibiotics in culture medium. Various fungi, bacteria, and yeast contaminants were identified and were tested against a range of antibiotics that were added to the culture medium. There were always a few cultures that remained clean for 3 - 5 weeks and when contaminants started to appear, an attempt to rescue these cultures by resterilizing and transferring to new medium failed due to phytotoxicity effects. The use of explants from the treated plants is preferred as they showed a limited degree of contamination and delayed the appearance of contaminants. The decontamination strategies suggested are based on the results of these decontamination procedure investigations and the knowledge of the phytotoxicity effects of the disinfectants and antibiotics on kava.