Problems in tissue culture: culture contamination

Abstract

Contamination in tissue culture can originate from two sources, either through carry over of microorganisms on the surface or in the tissues of explants, or through faulty procedures in the laboratory. Plant surfaces are habitats for microorganisms (Campbell, 1985). In the course of plant growth and development many surface and rhizosphere-inhabiting microorganisms may enter the tissues of the plant through natural openings, wounds etc. opportunistically and to varying extents colonise the plant tissues. In addition, facultative and obligate pathogens may colonise plants similarly, be vector assisted or possess host plant penetration mechanisms (Tarr, 1972; Matthews, 1981). Plants may thus develop endophytic ‘floras' of variable species composition consisting of inter-and intracellular microorganisms including viruses, viroids, prokaryotes (bacterial and bacteria-like agents) and fungi. In establishing tissue cultures, depending on the explant used, surface and endophytic microorganisms may be carried over into culture. In meristem culture, depending on meristem size most organisms will be eliminated whereas in leaf, petiole or stem explant, most if not all microorganisms in the tissues may be carried over.