Elimination of systemic contamination in explant and protoplast cultures of rubber (Hevea brasiliensis Muell. Arg.)

Ten systemic microorganisms (bacteria and yeasts) were isolated from stem sections of ex vitro grown rubber plants. Antibiotics were screened for their efficacy against these microorganisms and for possible tissue phytotoxicity. Erythromycin, nystatin and streptomycin at bactericidal levels were asymptomatic in relation to tissue stress nor was callusing capacity reduced. Contamination of stem explants as used for callus initiation, was reduced from 95.8 to 43.8% by the incorporation of these three antibiotics, at concentrations of 32.0, 16.0, 16.0 g/ml respectively. Contamination was eliminated from protoplast cultures by these antibiotics, at half strength, in the plasmolysis and enzyme solutions. Rubber protoplast survival was promoted by these antibiotics.Abbreviations WPM woody plant medium (Lloyd and McCown 1981) - 24D 2,4-dichlorophenoxyacetic acid - KN kinetin - WPMDKN woody plant basal medium supplemented with 2.0 mg/l 24D and 0.5 mg/l KN - MS Murashige and Skoog (1962) - ery. erythromycin - ny. nystatin - strep. streptomycin sulphate - tet. tetracycline (all Sigma) - FDA fluorescein diacetate - MIC minimum inhibitory concentration