Screening Antibiotics for the Elimination of Bacteria from in vitro Yam Plantlets

Abstract

Plant tissue culture technology has been successfully used for the commercial production of pathogen-free plants and for germplasm conservation of rare and endangered species. Clean cultures of aseptically micropropagated shoot cultures of the genus Dioscorea (yam) grown on yam multiplication media are often contaminated with covert bacteria. The bacteria may survive endophytically within these plantlets thereby making the plantlets unusable for in vitro maintenance of germplasm. This study aimed at screening some antibiotics with a view of identifying the best one that can eradicate these endophytic bacteria from yam germplasm maintained in vitro. Eleven antibiotics, at different concentration range, were evaluated on the identified isolates to determine their potential to inhibit these contaminants, using the disk diffusion technique. Single or combined antibiotic treatments effective against the contaminants were also screened for their stability and minimum bactericidal concentration (MBC). The results shows that tetracycline combined with rifampicin (TR), streptomycin plus gentamycin (SG), rifampicin (Rn), vancomycin plus streptomycin (VS) at ≥ 125 μg/ml and TVSGR (tetracycline + vancomycin + streptomycin + gentamycin + rifampicin) at ≥ 100 μg/ml were highly bactericidal. These potential bactericidal doses can be further tested in vivo to determine their efficacy in the eradication of bacterial contaminants from the in vitro yam tissue cultured.