ABSTRACT
Research and commercial tissue culture laboratories often use only visual methods to index for culture contamination (the so-called EBD or eyeball determination method). There are several important reasons why screening only for visible microbial contamination is not adequate. Visible growth of microbial contaminants may be suppressed in plant culture media (Leifert and Waites, 1992). Although many fungal contaminants quickly become visible, endophytic bacterial infections may be latent and difcult to detect (Tanprasert and Reed, 1997; Thomas, 2004). Microbial contaminants such as Methylobacteria have evolved close biochemical relationships with the plant epidermis in vivo and will not grow independently on standard plant culture media (Holland and Polacco, 1994).
